Adding upstream version 5.10.209.upstream/5.10.209

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1444 insertions, 0 deletions

diff --git a/arch/powerpc/platforms/powernv/vas-window.c b/arch/powerpc/platforms/powernv/vas-window.c
new file mode 100644
index 000000000..3a86cdd5a
--- /dev/null
+++ b/arch/powerpc/platforms/powernv/vas-window.c
@@ -0,0 +1,1444 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright 2016-17 IBM Corp.
+ */
+
+#define pr_fmt(fmt) "vas: " fmt
+
+#include <linux/types.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/io.h>
+#include <linux/log2.h>
+#include <linux/rcupdate.h>
+#include <linux/cred.h>
+#include <linux/sched/mm.h>
+#include <linux/mmu_context.h>
+#include <asm/switch_to.h>
+#include <asm/ppc-opcode.h>
+#include "vas.h"
+#include "copy-paste.h"
+
+#define CREATE_TRACE_POINTS
+#include "vas-trace.h"
+
+/*
+ * Compute the paste address region for the window @window using the
+ * ->paste_base_addr and ->paste_win_id_shift we got from device tree.
+ */
+void vas_win_paste_addr(struct vas_window *window, u64 *addr, int *len)
+{
+	int winid;
+	u64 base, shift;
+
+	base = window->vinst->paste_base_addr;
+	shift = window->vinst->paste_win_id_shift;
+	winid = window->winid;
+
+	*addr  = base + (winid << shift);
+	if (len)
+		*len = PAGE_SIZE;
+
+	pr_debug("Txwin #%d: Paste addr 0x%llx\n", winid, *addr);
+}
+
+static inline void get_hvwc_mmio_bar(struct vas_window *window,
+			u64 *start, int *len)
+{
+	u64 pbaddr;
+
+	pbaddr = window->vinst->hvwc_bar_start;
+	*start = pbaddr + window->winid * VAS_HVWC_SIZE;
+	*len = VAS_HVWC_SIZE;
+}
+
+static inline void get_uwc_mmio_bar(struct vas_window *window,
+			u64 *start, int *len)
+{
+	u64 pbaddr;
+
+	pbaddr = window->vinst->uwc_bar_start;
+	*start = pbaddr + window->winid * VAS_UWC_SIZE;
+	*len = VAS_UWC_SIZE;
+}
+
+/*
+ * Map the paste bus address of the given send window into kernel address
+ * space. Unlike MMIO regions (map_mmio_region() below), paste region must
+ * be mapped cache-able and is only applicable to send windows.
+ */
+static void *map_paste_region(struct vas_window *txwin)
+{
+	int len;
+	void *map;
+	char *name;
+	u64 start;
+
+	name = kasprintf(GFP_KERNEL, "window-v%d-w%d", txwin->vinst->vas_id,
+				txwin->winid);
+	if (!name)
+		goto free_name;
+
+	txwin->paste_addr_name = name;
+	vas_win_paste_addr(txwin, &start, &len);
+
+	if (!request_mem_region(start, len, name)) {
+		pr_devel("%s(): request_mem_region(0x%llx, %d) failed\n",
+				__func__, start, len);
+		goto free_name;
+	}
+
+	map = ioremap_cache(start, len);
+	if (!map) {
+		pr_devel("%s(): ioremap_cache(0x%llx, %d) failed\n", __func__,
+				start, len);
+		goto free_name;
+	}
+
+	pr_devel("Mapped paste addr 0x%llx to kaddr 0x%p\n", start, map);
+	return map;
+
+free_name:
+	kfree(name);
+	return ERR_PTR(-ENOMEM);
+}
+
+static void *map_mmio_region(char *name, u64 start, int len)
+{
+	void *map;
+
+	if (!request_mem_region(start, len, name)) {
+		pr_devel("%s(): request_mem_region(0x%llx, %d) failed\n",
+				__func__, start, len);
+		return NULL;
+	}
+
+	map = ioremap(start, len);
+	if (!map) {
+		pr_devel("%s(): ioremap(0x%llx, %d) failed\n", __func__, start,
+				len);
+		return NULL;
+	}
+
+	return map;
+}
+
+static void unmap_region(void *addr, u64 start, int len)
+{
+	iounmap(addr);
+	release_mem_region((phys_addr_t)start, len);
+}
+
+/*
+ * Unmap the paste address region for a window.
+ */
+static void unmap_paste_region(struct vas_window *window)
+{
+	int len;
+	u64 busaddr_start;
+
+	if (window->paste_kaddr) {
+		vas_win_paste_addr(window, &busaddr_start, &len);
+		unmap_region(window->paste_kaddr, busaddr_start, len);
+		window->paste_kaddr = NULL;
+		kfree(window->paste_addr_name);
+		window->paste_addr_name = NULL;
+	}
+}
+
+/*
+ * Unmap the MMIO regions for a window. Hold the vas_mutex so we don't
+ * unmap when the window's debugfs dir is in use. This serializes close
+ * of a window even on another VAS instance but since its not a critical
+ * path, just minimize the time we hold the mutex for now. We can add
+ * a per-instance mutex later if necessary.
+ */
+static void unmap_winctx_mmio_bars(struct vas_window *window)
+{
+	int len;
+	void *uwc_map;
+	void *hvwc_map;
+	u64 busaddr_start;
+
+	mutex_lock(&vas_mutex);
+
+	hvwc_map = window->hvwc_map;
+	window->hvwc_map = NULL;
+
+	uwc_map = window->uwc_map;
+	window->uwc_map = NULL;
+
+	mutex_unlock(&vas_mutex);
+
+	if (hvwc_map) {
+		get_hvwc_mmio_bar(window, &busaddr_start, &len);
+		unmap_region(hvwc_map, busaddr_start, len);
+	}
+
+	if (uwc_map) {
+		get_uwc_mmio_bar(window, &busaddr_start, &len);
+		unmap_region(uwc_map, busaddr_start, len);
+	}
+}
+
+/*
+ * Find the Hypervisor Window Context (HVWC) MMIO Base Address Region and the
+ * OS/User Window Context (UWC) MMIO Base Address Region for the given window.
+ * Map these bus addresses and save the mapped kernel addresses in @window.
+ */
+static int map_winctx_mmio_bars(struct vas_window *window)
+{
+	int len;
+	u64 start;
+
+	get_hvwc_mmio_bar(window, &start, &len);
+	window->hvwc_map = map_mmio_region("HVWCM_Window", start, len);
+
+	get_uwc_mmio_bar(window, &start, &len);
+	window->uwc_map = map_mmio_region("UWCM_Window", start, len);
+
+	if (!window->hvwc_map || !window->uwc_map) {
+		unmap_winctx_mmio_bars(window);
+		return -1;
+	}
+
+	return 0;
+}
+
+/*
+ * Reset all valid registers in the HV and OS/User Window Contexts for
+ * the window identified by @window.
+ *
+ * NOTE: We cannot really use a for loop to reset window context. Not all
+ *	 offsets in a window context are valid registers and the valid
+ *	 registers are not sequential. And, we can only write to offsets
+ *	 with valid registers.
+ */
+static void reset_window_regs(struct vas_window *window)
+{
+	write_hvwc_reg(window, VREG(LPID), 0ULL);
+	write_hvwc_reg(window, VREG(PID), 0ULL);
+	write_hvwc_reg(window, VREG(XLATE_MSR), 0ULL);
+	write_hvwc_reg(window, VREG(XLATE_LPCR), 0ULL);
+	write_hvwc_reg(window, VREG(XLATE_CTL), 0ULL);
+	write_hvwc_reg(window, VREG(AMR), 0ULL);
+	write_hvwc_reg(window, VREG(SEIDR), 0ULL);
+	write_hvwc_reg(window, VREG(FAULT_TX_WIN), 0ULL);
+	write_hvwc_reg(window, VREG(OSU_INTR_SRC_RA), 0ULL);
+	write_hvwc_reg(window, VREG(HV_INTR_SRC_RA), 0ULL);
+	write_hvwc_reg(window, VREG(PSWID), 0ULL);
+	write_hvwc_reg(window, VREG(LFIFO_BAR), 0ULL);
+	write_hvwc_reg(window, VREG(LDATA_STAMP_CTL), 0ULL);
+	write_hvwc_reg(window, VREG(LDMA_CACHE_CTL), 0ULL);
+	write_hvwc_reg(window, VREG(LRFIFO_PUSH), 0ULL);
+	write_hvwc_reg(window, VREG(CURR_MSG_COUNT), 0ULL);
+	write_hvwc_reg(window, VREG(LNOTIFY_AFTER_COUNT), 0ULL);
+	write_hvwc_reg(window, VREG(LRX_WCRED), 0ULL);
+	write_hvwc_reg(window, VREG(LRX_WCRED_ADDER), 0ULL);
+	write_hvwc_reg(window, VREG(TX_WCRED), 0ULL);
+	write_hvwc_reg(window, VREG(TX_WCRED_ADDER), 0ULL);
+	write_hvwc_reg(window, VREG(LFIFO_SIZE), 0ULL);
+	write_hvwc_reg(window, VREG(WINCTL), 0ULL);
+	write_hvwc_reg(window, VREG(WIN_STATUS), 0ULL);
+	write_hvwc_reg(window, VREG(WIN_CTX_CACHING_CTL), 0ULL);
+	write_hvwc_reg(window, VREG(TX_RSVD_BUF_COUNT), 0ULL);
+	write_hvwc_reg(window, VREG(LRFIFO_WIN_PTR), 0ULL);
+	write_hvwc_reg(window, VREG(LNOTIFY_CTL), 0ULL);
+	write_hvwc_reg(window, VREG(LNOTIFY_PID), 0ULL);
+	write_hvwc_reg(window, VREG(LNOTIFY_LPID), 0ULL);
+	write_hvwc_reg(window, VREG(LNOTIFY_TID), 0ULL);
+	write_hvwc_reg(window, VREG(LNOTIFY_SCOPE), 0ULL);
+	write_hvwc_reg(window, VREG(NX_UTIL_ADDER), 0ULL);
+
+	/* Skip read-only registers: NX_UTIL and NX_UTIL_SE */
+
+	/*
+	 * The send and receive window credit adder registers are also
+	 * accessible from HVWC and have been initialized above. We don't
+	 * need to initialize from the OS/User Window Context, so skip
+	 * following calls:
+	 *
+	 *	write_uwc_reg(window, VREG(TX_WCRED_ADDER), 0ULL);
+	 *	write_uwc_reg(window, VREG(LRX_WCRED_ADDER), 0ULL);
+	 */
+}
+
+/*
+ * Initialize window context registers related to Address Translation.
+ * These registers are common to send/receive windows although they
+ * differ for user/kernel windows. As we resolve the TODOs we may
+ * want to add fields to vas_winctx and move the initialization to
+ * init_vas_winctx_regs().
+ */
+static void init_xlate_regs(struct vas_window *window, bool user_win)
+{
+	u64 lpcr, val;
+
+	/*
+	 * MSR_TA, MSR_US are false for both kernel and user.
+	 * MSR_DR and MSR_PR are false for kernel.
+	 */
+	val = 0ULL;
+	val = SET_FIELD(VAS_XLATE_MSR_HV, val, 1);
+	val = SET_FIELD(VAS_XLATE_MSR_SF, val, 1);
+	if (user_win) {
+		val = SET_FIELD(VAS_XLATE_MSR_DR, val, 1);
+		val = SET_FIELD(VAS_XLATE_MSR_PR, val, 1);
+	}
+	write_hvwc_reg(window, VREG(XLATE_MSR), val);
+
+	lpcr = mfspr(SPRN_LPCR);
+	val = 0ULL;
+	/*
+	 * NOTE: From Section 5.7.8.1 Segment Lookaside Buffer of the
+	 *	 Power ISA, v3.0B, Page size encoding is 0 = 4KB, 5 = 64KB.
+	 *
+	 * NOTE: From Section 1.3.1, Address Translation Context of the
+	 *	 Nest MMU Workbook, LPCR_SC should be 0 for Power9.
+	 */
+	val = SET_FIELD(VAS_XLATE_LPCR_PAGE_SIZE, val, 5);
+	val = SET_FIELD(VAS_XLATE_LPCR_ISL, val, lpcr & LPCR_ISL);
+	val = SET_FIELD(VAS_XLATE_LPCR_TC, val, lpcr & LPCR_TC);
+	val = SET_FIELD(VAS_XLATE_LPCR_SC, val, 0);
+	write_hvwc_reg(window, VREG(XLATE_LPCR), val);
+
+	/*
+	 * Section 1.3.1 (Address translation Context) of NMMU workbook.
+	 *	0b00	Hashed Page Table mode
+	 *	0b01	Reserved
+	 *	0b10	Radix on HPT
+	 *	0b11	Radix on Radix
+	 */
+	val = 0ULL;
+	val = SET_FIELD(VAS_XLATE_MODE, val, radix_enabled() ? 3 : 2);
+	write_hvwc_reg(window, VREG(XLATE_CTL), val);
+
+	/*
+	 * TODO: Can we mfspr(AMR) even for user windows?
+	 */
+	val = 0ULL;
+	val = SET_FIELD(VAS_AMR, val, mfspr(SPRN_AMR));
+	write_hvwc_reg(window, VREG(AMR), val);
+
+	val = 0ULL;
+	val = SET_FIELD(VAS_SEIDR, val, 0);
+	write_hvwc_reg(window, VREG(SEIDR), val);
+}
+
+/*
+ * Initialize Reserved Send Buffer Count for the send window. It involves
+ * writing to the register, reading it back to confirm that the hardware
+ * has enough buffers to reserve. See section 1.3.1.2.1 of VAS workbook.
+ *
+ * Since we can only make a best-effort attempt to fulfill the request,
+ * we don't return any errors if we cannot.
+ *
+ * TODO: Reserved (aka dedicated) send buffers are not supported yet.
+ */
+static void init_rsvd_tx_buf_count(struct vas_window *txwin,
+				struct vas_winctx *winctx)
+{
+	write_hvwc_reg(txwin, VREG(TX_RSVD_BUF_COUNT), 0ULL);
+}
+
+/*
+ * init_winctx_regs()
+ *	Initialize window context registers for a receive window.
+ *	Except for caching control and marking window open, the registers
+ *	are initialized in the order listed in Section 3.1.4 (Window Context
+ *	Cache Register Details) of the VAS workbook although they don't need
+ *	to be.
+ *
+ * Design note: For NX receive windows, NX allocates the FIFO buffer in OPAL
+ *	(so that it can get a large contiguous area) and passes that buffer
+ *	to kernel via device tree. We now write that buffer address to the
+ *	FIFO BAR. Would it make sense to do this all in OPAL? i.e have OPAL
+ *	write the per-chip RX FIFO addresses to the windows during boot-up
+ *	as a one-time task? That could work for NX but what about other
+ *	receivers?  Let the receivers tell us the rx-fifo buffers for now.
+ */
+static void init_winctx_regs(struct vas_window *window,
+			     struct vas_winctx *winctx)
+{
+	u64 val;
+	int fifo_size;
+
+	reset_window_regs(window);
+
+	val = 0ULL;
+	val = SET_FIELD(VAS_LPID, val, winctx->lpid);
+	write_hvwc_reg(window, VREG(LPID), val);
+
+	val = 0ULL;
+	val = SET_FIELD(VAS_PID_ID, val, winctx->pidr);
+	write_hvwc_reg(window, VREG(PID), val);
+
+	init_xlate_regs(window, winctx->user_win);
+
+	val = 0ULL;
+	val = SET_FIELD(VAS_FAULT_TX_WIN, val, winctx->fault_win_id);
+	write_hvwc_reg(window, VREG(FAULT_TX_WIN), val);
+
+	/* In PowerNV, interrupts go to HV. */
+	write_hvwc_reg(window, VREG(OSU_INTR_SRC_RA), 0ULL);
+
+	val = 0ULL;
+	val = SET_FIELD(VAS_HV_INTR_SRC_RA, val, winctx->irq_port);
+	write_hvwc_reg(window, VREG(HV_INTR_SRC_RA), val);
+
+	val = 0ULL;
+	val = SET_FIELD(VAS_PSWID_EA_HANDLE, val, winctx->pswid);
+	write_hvwc_reg(window, VREG(PSWID), val);
+
+	write_hvwc_reg(window, VREG(SPARE1), 0ULL);
+	write_hvwc_reg(window, VREG(SPARE2), 0ULL);
+	write_hvwc_reg(window, VREG(SPARE3), 0ULL);
+
+	/*
+	 * NOTE: VAS expects the FIFO address to be copied into the LFIFO_BAR
+	 *	 register as is - do NOT shift the address into VAS_LFIFO_BAR
+	 *	 bit fields! Ok to set the page migration select fields -
+	 *	 VAS ignores the lower 10+ bits in the address anyway, because
+	 *	 the minimum FIFO size is 1K?
+	 *
+	 * See also: Design note in function header.
+	 */
+	val = winctx->rx_fifo;
+	val = SET_FIELD(VAS_PAGE_MIGRATION_SELECT, val, 0);
+	write_hvwc_reg(window, VREG(LFIFO_BAR), val);
+
+	val = 0ULL;
+	val = SET_FIELD(VAS_LDATA_STAMP, val, winctx->data_stamp);
+	write_hvwc_reg(window, VREG(LDATA_STAMP_CTL), val);
+
+	val = 0ULL;
+	val = SET_FIELD(VAS_LDMA_TYPE, val, winctx->dma_type);
+	val = SET_FIELD(VAS_LDMA_FIFO_DISABLE, val, winctx->fifo_disable);
+	write_hvwc_reg(window, VREG(LDMA_CACHE_CTL), val);
+
+	write_hvwc_reg(window, VREG(LRFIFO_PUSH), 0ULL);
+	write_hvwc_reg(window, VREG(CURR_MSG_COUNT), 0ULL);
+	write_hvwc_reg(window, VREG(LNOTIFY_AFTER_COUNT), 0ULL);
+
+	val = 0ULL;
+	val = SET_FIELD(VAS_LRX_WCRED, val, winctx->wcreds_max);
+	write_hvwc_reg(window, VREG(LRX_WCRED), val);
+
+	val = 0ULL;
+	val = SET_FIELD(VAS_TX_WCRED, val, winctx->wcreds_max);
+	write_hvwc_reg(window, VREG(TX_WCRED), val);
+
+	write_hvwc_reg(window, VREG(LRX_WCRED_ADDER), 0ULL);
+	write_hvwc_reg(window, VREG(TX_WCRED_ADDER), 0ULL);
+
+	fifo_size = winctx->rx_fifo_size / 1024;
+
+	val = 0ULL;
+	val = SET_FIELD(VAS_LFIFO_SIZE, val, ilog2(fifo_size));
+	write_hvwc_reg(window, VREG(LFIFO_SIZE), val);
+
+	/* Update window control and caching control registers last so
+	 * we mark the window open only after fully initializing it and
+	 * pushing context to cache.
+	 */
+
+	write_hvwc_reg(window, VREG(WIN_STATUS), 0ULL);
+
+	init_rsvd_tx_buf_count(window, winctx);
+
+	/* for a send window, point to the matching receive window */
+	val = 0ULL;
+	val = SET_FIELD(VAS_LRX_WIN_ID, val, winctx->rx_win_id);
+	write_hvwc_reg(window, VREG(LRFIFO_WIN_PTR), val);
+
+	write_hvwc_reg(window, VREG(SPARE4), 0ULL);
+
+	val = 0ULL;
+	val = SET_FIELD(VAS_NOTIFY_DISABLE, val, winctx->notify_disable);
+	val = SET_FIELD(VAS_INTR_DISABLE, val, winctx->intr_disable);
+	val = SET_FIELD(VAS_NOTIFY_EARLY, val, winctx->notify_early);
+	val = SET_FIELD(VAS_NOTIFY_OSU_INTR, val, winctx->notify_os_intr_reg);
+	write_hvwc_reg(window, VREG(LNOTIFY_CTL), val);
+
+	val = 0ULL;
+	val = SET_FIELD(VAS_LNOTIFY_PID, val, winctx->lnotify_pid);
+	write_hvwc_reg(window, VREG(LNOTIFY_PID), val);
+
+	val = 0ULL;
+	val = SET_FIELD(VAS_LNOTIFY_LPID, val, winctx->lnotify_lpid);
+	write_hvwc_reg(window, VREG(LNOTIFY_LPID), val);
+
+	val = 0ULL;
+	val = SET_FIELD(VAS_LNOTIFY_TID, val, winctx->lnotify_tid);
+	write_hvwc_reg(window, VREG(LNOTIFY_TID), val);
+
+	val = 0ULL;
+	val = SET_FIELD(VAS_LNOTIFY_MIN_SCOPE, val, winctx->min_scope);
+	val = SET_FIELD(VAS_LNOTIFY_MAX_SCOPE, val, winctx->max_scope);
+	write_hvwc_reg(window, VREG(LNOTIFY_SCOPE), val);
+
+	/* Skip read-only registers NX_UTIL and NX_UTIL_SE */
+
+	write_hvwc_reg(window, VREG(SPARE5), 0ULL);
+	write_hvwc_reg(window, VREG(NX_UTIL_ADDER), 0ULL);
+	write_hvwc_reg(window, VREG(SPARE6), 0ULL);
+
+	/* Finally, push window context to memory and... */
+	val = 0ULL;
+	val = SET_FIELD(VAS_PUSH_TO_MEM, val, 1);
+	write_hvwc_reg(window, VREG(WIN_CTX_CACHING_CTL), val);
+
+	/* ... mark the window open for business */
+	val = 0ULL;
+	val = SET_FIELD(VAS_WINCTL_REJ_NO_CREDIT, val, winctx->rej_no_credit);
+	val = SET_FIELD(VAS_WINCTL_PIN, val, winctx->pin_win);
+	val = SET_FIELD(VAS_WINCTL_TX_WCRED_MODE, val, winctx->tx_wcred_mode);
+	val = SET_FIELD(VAS_WINCTL_RX_WCRED_MODE, val, winctx->rx_wcred_mode);
+	val = SET_FIELD(VAS_WINCTL_TX_WORD_MODE, val, winctx->tx_word_mode);
+	val = SET_FIELD(VAS_WINCTL_RX_WORD_MODE, val, winctx->rx_word_mode);
+	val = SET_FIELD(VAS_WINCTL_FAULT_WIN, val, winctx->fault_win);
+	val = SET_FIELD(VAS_WINCTL_NX_WIN, val, winctx->nx_win);
+	val = SET_FIELD(VAS_WINCTL_OPEN, val, 1);
+	write_hvwc_reg(window, VREG(WINCTL), val);
+}
+
+static void vas_release_window_id(struct ida *ida, int winid)
+{
+	ida_free(ida, winid);
+}
+
+static int vas_assign_window_id(struct ida *ida)
+{
+	int winid = ida_alloc_max(ida, VAS_WINDOWS_PER_CHIP - 1, GFP_KERNEL);
+
+	if (winid == -ENOSPC) {
+		pr_err("Too many (%d) open windows\n", VAS_WINDOWS_PER_CHIP);
+		return -EAGAIN;
+	}
+
+	return winid;
+}
+
+static void vas_window_free(struct vas_window *window)
+{
+	int winid = window->winid;
+	struct vas_instance *vinst = window->vinst;
+
+	unmap_winctx_mmio_bars(window);
+
+	vas_window_free_dbgdir(window);
+
+	kfree(window);
+
+	vas_release_window_id(&vinst->ida, winid);
+}
+
+static struct vas_window *vas_window_alloc(struct vas_instance *vinst)
+{
+	int winid;
+	struct vas_window *window;
+
+	winid = vas_assign_window_id(&vinst->ida);
+	if (winid < 0)
+		return ERR_PTR(winid);
+
+	window = kzalloc(sizeof(*window), GFP_KERNEL);
+	if (!window)
+		goto out_free;
+
+	window->vinst = vinst;
+	window->winid = winid;
+
+	if (map_winctx_mmio_bars(window))
+		goto out_free;
+
+	vas_window_init_dbgdir(window);
+
+	return window;
+
+out_free:
+	kfree(window);
+	vas_release_window_id(&vinst->ida, winid);
+	return ERR_PTR(-ENOMEM);
+}
+
+static void put_rx_win(struct vas_window *rxwin)
+{
+	/* Better not be a send window! */
+	WARN_ON_ONCE(rxwin->tx_win);
+
+	atomic_dec(&rxwin->num_txwins);
+}
+
+/*
+ * Find the user space receive window given the @pswid.
+ *      - We must have a valid vasid and it must belong to this instance.
+ *        (so both send and receive windows are on the same VAS instance)
+ *      - The window must refer to an OPEN, FTW, RECEIVE window.
+ *
+ * NOTE: We access ->windows[] table and assume that vinst->mutex is held.
+ */
+static struct vas_window *get_user_rxwin(struct vas_instance *vinst, u32 pswid)
+{
+	int vasid, winid;
+	struct vas_window *rxwin;
+
+	decode_pswid(pswid, &vasid, &winid);
+
+	if (vinst->vas_id != vasid)
+		return ERR_PTR(-EINVAL);
+
+	rxwin = vinst->windows[winid];
+
+	if (!rxwin || rxwin->tx_win || rxwin->cop != VAS_COP_TYPE_FTW)
+		return ERR_PTR(-EINVAL);
+
+	return rxwin;
+}
+
+/*
+ * Get the VAS receive window associated with NX engine identified
+ * by @cop and if applicable, @pswid.
+ *
+ * See also function header of set_vinst_win().
+ */
+static struct vas_window *get_vinst_rxwin(struct vas_instance *vinst,
+			enum vas_cop_type cop, u32 pswid)
+{
+	struct vas_window *rxwin;
+
+	mutex_lock(&vinst->mutex);
+
+	if (cop == VAS_COP_TYPE_FTW)
+		rxwin = get_user_rxwin(vinst, pswid);
+	else
+		rxwin = vinst->rxwin[cop] ?: ERR_PTR(-EINVAL);
+
+	if (!IS_ERR(rxwin))
+		atomic_inc(&rxwin->num_txwins);
+
+	mutex_unlock(&vinst->mutex);
+
+	return rxwin;
+}
+
+/*
+ * We have two tables of windows in a VAS instance. The first one,
+ * ->windows[], contains all the windows in the instance and allows
+ * looking up a window by its id. It is used to look up send windows
+ * during fault handling and receive windows when pairing user space
+ * send/receive windows.
+ *
+ * The second table, ->rxwin[], contains receive windows that are
+ * associated with NX engines. This table has VAS_COP_TYPE_MAX
+ * entries and is used to look up a receive window by its
+ * coprocessor type.
+ *
+ * Here, we save @window in the ->windows[] table. If it is a receive
+ * window, we also save the window in the ->rxwin[] table.
+ */
+static void set_vinst_win(struct vas_instance *vinst,
+			struct vas_window *window)
+{
+	int id = window->winid;
+
+	mutex_lock(&vinst->mutex);
+
+	/*
+	 * There should only be one receive window for a coprocessor type
+	 * unless its a user (FTW) window.
+	 */
+	if (!window->user_win && !window->tx_win) {
+		WARN_ON_ONCE(vinst->rxwin[window->cop]);
+		vinst->rxwin[window->cop] = window;
+	}
+
+	WARN_ON_ONCE(vinst->windows[id] != NULL);
+	vinst->windows[id] = window;
+
+	mutex_unlock(&vinst->mutex);
+}
+
+/*
+ * Clear this window from the table(s) of windows for this VAS instance.
+ * See also function header of set_vinst_win().
+ */
+static void clear_vinst_win(struct vas_window *window)
+{
+	int id = window->winid;
+	struct vas_instance *vinst = window->vinst;
+
+	mutex_lock(&vinst->mutex);
+
+	if (!window->user_win && !window->tx_win) {
+		WARN_ON_ONCE(!vinst->rxwin[window->cop]);
+		vinst->rxwin[window->cop] = NULL;
+	}
+
+	WARN_ON_ONCE(vinst->windows[id] != window);
+	vinst->windows[id] = NULL;
+
+	mutex_unlock(&vinst->mutex);
+}
+
+static void init_winctx_for_rxwin(struct vas_window *rxwin,
+			struct vas_rx_win_attr *rxattr,
+			struct vas_winctx *winctx)
+{
+	/*
+	 * We first zero (memset()) all fields and only set non-zero fields.
+	 * Following fields are 0/false but maybe deserve a comment:
+	 *
+	 *	->notify_os_intr_reg	In powerNV, send intrs to HV
+	 *	->notify_disable	False for NX windows
+	 *	->intr_disable		False for Fault Windows
+	 *	->xtra_write		False for NX windows
+	 *	->notify_early		NA for NX windows
+	 *	->rsvd_txbuf_count	NA for Rx windows
+	 *	->lpid, ->pid, ->tid	NA for Rx windows
+	 */
+
+	memset(winctx, 0, sizeof(struct vas_winctx));
+
+	winctx->rx_fifo = rxattr->rx_fifo;
+	winctx->rx_fifo_size = rxattr->rx_fifo_size;
+	winctx->wcreds_max = rxwin->wcreds_max;
+	winctx->pin_win = rxattr->pin_win;
+
+	winctx->nx_win = rxattr->nx_win;
+	winctx->fault_win = rxattr->fault_win;
+	winctx->user_win = rxattr->user_win;
+	winctx->rej_no_credit = rxattr->rej_no_credit;
+	winctx->rx_word_mode = rxattr->rx_win_ord_mode;
+	winctx->tx_word_mode = rxattr->tx_win_ord_mode;
+	winctx->rx_wcred_mode = rxattr->rx_wcred_mode;
+	winctx->tx_wcred_mode = rxattr->tx_wcred_mode;
+	winctx->notify_early = rxattr->notify_early;
+
+	if (winctx->nx_win) {
+		winctx->data_stamp = true;
+		winctx->intr_disable = true;
+		winctx->pin_win = true;
+
+		WARN_ON_ONCE(winctx->fault_win);
+		WARN_ON_ONCE(!winctx->rx_word_mode);
+		WARN_ON_ONCE(!winctx->tx_word_mode);
+		WARN_ON_ONCE(winctx->notify_after_count);
+	} else if (winctx->fault_win) {
+		winctx->notify_disable = true;
+	} else if (winctx->user_win) {
+		/*
+		 * Section 1.8.1 Low Latency Core-Core Wake up of
+		 * the VAS workbook:
+		 *
+		 *      - disable credit checks ([tr]x_wcred_mode = false)
+		 *      - disable FIFO writes
+		 *      - enable ASB_Notify, disable interrupt
+		 */
+		winctx->fifo_disable = true;
+		winctx->intr_disable = true;
+		winctx->rx_fifo = 0;
+	}
+
+	winctx->lnotify_lpid = rxattr->lnotify_lpid;
+	winctx->lnotify_pid = rxattr->lnotify_pid;
+	winctx->lnotify_tid = rxattr->lnotify_tid;
+	winctx->pswid = rxattr->pswid;
+	winctx->dma_type = VAS_DMA_TYPE_INJECT;
+	winctx->tc_mode = rxattr->tc_mode;
+
+	winctx->min_scope = VAS_SCOPE_LOCAL;
+	winctx->max_scope = VAS_SCOPE_VECTORED_GROUP;
+	if (rxwin->vinst->virq)
+		winctx->irq_port = rxwin->vinst->irq_port;
+}
+
+static bool rx_win_args_valid(enum vas_cop_type cop,
+			struct vas_rx_win_attr *attr)
+{
+	pr_debug("Rxattr: fault %d, notify %d, intr %d, early %d, fifo %d\n",
+			attr->fault_win, attr->notify_disable,
+			attr->intr_disable, attr->notify_early,
+			attr->rx_fifo_size);
+
+	if (cop >= VAS_COP_TYPE_MAX)
+		return false;
+
+	if (cop != VAS_COP_TYPE_FTW &&
+				attr->rx_fifo_size < VAS_RX_FIFO_SIZE_MIN)
+		return false;
+
+	if (attr->rx_fifo_size > VAS_RX_FIFO_SIZE_MAX)
+		return false;
+
+	if (!attr->wcreds_max)
+		return false;
+
+	if (attr->nx_win) {
+		/* cannot be fault or user window if it is nx */
+		if (attr->fault_win || attr->user_win)
+			return false;
+		/*
+		 * Section 3.1.4.32: NX Windows must not disable notification,
+		 *	and must not enable interrupts or early notification.
+		 */
+		if (attr->notify_disable || !attr->intr_disable ||
+				attr->notify_early)
+			return false;
+	} else if (attr->fault_win) {
+		/* cannot be both fault and user window */
+		if (attr->user_win)
+			return false;
+
+		/*
+		 * Section 3.1.4.32: Fault windows must disable notification
+		 *	but not interrupts.
+		 */
+		if (!attr->notify_disable || attr->intr_disable)
+			return false;
+
+	} else if (attr->user_win) {
+		/*
+		 * User receive windows are only for fast-thread-wakeup
+		 * (FTW). They don't need a FIFO and must disable interrupts
+		 */
+		if (attr->rx_fifo || attr->rx_fifo_size || !attr->intr_disable)
+			return false;
+	} else {
+		/* Rx window must be one of NX or Fault or User window. */
+		return false;
+	}
+
+	return true;
+}
+
+void vas_init_rx_win_attr(struct vas_rx_win_attr *rxattr, enum vas_cop_type cop)
+{
+	memset(rxattr, 0, sizeof(*rxattr));
+
+	if (cop == VAS_COP_TYPE_842 || cop == VAS_COP_TYPE_842_HIPRI ||
+		cop == VAS_COP_TYPE_GZIP || cop == VAS_COP_TYPE_GZIP_HIPRI) {
+		rxattr->pin_win = true;
+		rxattr->nx_win = true;
+		rxattr->fault_win = false;
+		rxattr->intr_disable = true;
+		rxattr->rx_wcred_mode = true;
+		rxattr->tx_wcred_mode = true;
+		rxattr->rx_win_ord_mode = true;
+		rxattr->tx_win_ord_mode = true;
+	} else if (cop == VAS_COP_TYPE_FAULT) {
+		rxattr->pin_win = true;
+		rxattr->fault_win = true;
+		rxattr->notify_disable = true;
+		rxattr->rx_wcred_mode = true;
+		rxattr->rx_win_ord_mode = true;
+		rxattr->rej_no_credit = true;
+		rxattr->tc_mode = VAS_THRESH_DISABLED;
+	} else if (cop == VAS_COP_TYPE_FTW) {
+		rxattr->user_win = true;
+		rxattr->intr_disable = true;
+
+		/*
+		 * As noted in the VAS Workbook we disable credit checks.
+		 * If we enable credit checks in the future, we must also
+		 * implement a mechanism to return the user credits or new
+		 * paste operations will fail.
+		 */
+	}
+}
+EXPORT_SYMBOL_GPL(vas_init_rx_win_attr);
+
+struct vas_window *vas_rx_win_open(int vasid, enum vas_cop_type cop,
+			struct vas_rx_win_attr *rxattr)
+{
+	struct vas_window *rxwin;
+	struct vas_winctx winctx;
+	struct vas_instance *vinst;
+
+	trace_vas_rx_win_open(current, vasid, cop, rxattr);
+
+	if (!rx_win_args_valid(cop, rxattr))
+		return ERR_PTR(-EINVAL);
+
+	vinst = find_vas_instance(vasid);
+	if (!vinst) {
+		pr_devel("vasid %d not found!\n", vasid);
+		return ERR_PTR(-EINVAL);
+	}
+	pr_devel("Found instance %d\n", vasid);
+
+	rxwin = vas_window_alloc(vinst);
+	if (IS_ERR(rxwin)) {
+		pr_devel("Unable to allocate memory for Rx window\n");
+		return rxwin;
+	}
+
+	rxwin->tx_win = false;
+	rxwin->nx_win = rxattr->nx_win;
+	rxwin->user_win = rxattr->user_win;
+	rxwin->cop = cop;
+	rxwin->wcreds_max = rxattr->wcreds_max;
+
+	init_winctx_for_rxwin(rxwin, rxattr, &winctx);
+	init_winctx_regs(rxwin, &winctx);
+
+	set_vinst_win(vinst, rxwin);
+
+	return rxwin;
+}
+EXPORT_SYMBOL_GPL(vas_rx_win_open);
+
+void vas_init_tx_win_attr(struct vas_tx_win_attr *txattr, enum vas_cop_type cop)
+{
+	memset(txattr, 0, sizeof(*txattr));
+
+	if (cop == VAS_COP_TYPE_842 || cop == VAS_COP_TYPE_842_HIPRI ||
+		cop == VAS_COP_TYPE_GZIP || cop == VAS_COP_TYPE_GZIP_HIPRI) {
+		txattr->rej_no_credit = false;
+		txattr->rx_wcred_mode = true;
+		txattr->tx_wcred_mode = true;
+		txattr->rx_win_ord_mode = true;
+		txattr->tx_win_ord_mode = true;
+	} else if (cop == VAS_COP_TYPE_FTW) {
+		txattr->user_win = true;
+	}
+}
+EXPORT_SYMBOL_GPL(vas_init_tx_win_attr);
+
+static void init_winctx_for_txwin(struct vas_window *txwin,
+			struct vas_tx_win_attr *txattr,
+			struct vas_winctx *winctx)
+{
+	/*
+	 * We first zero all fields and only set non-zero ones. Following
+	 * are some fields set to 0/false for the stated reason:
+	 *
+	 *	->notify_os_intr_reg	In powernv, send intrs to HV
+	 *	->rsvd_txbuf_count	Not supported yet.
+	 *	->notify_disable	False for NX windows
+	 *	->xtra_write		False for NX windows
+	 *	->notify_early		NA for NX windows
+	 *	->lnotify_lpid		NA for Tx windows
+	 *	->lnotify_pid		NA for Tx windows
+	 *	->lnotify_tid		NA for Tx windows
+	 *	->tx_win_cred_mode	Ignore for now for NX windows
+	 *	->rx_win_cred_mode	Ignore for now for NX windows
+	 */
+	memset(winctx, 0, sizeof(struct vas_winctx));
+
+	winctx->wcreds_max = txwin->wcreds_max;
+
+	winctx->user_win = txattr->user_win;
+	winctx->nx_win = txwin->rxwin->nx_win;
+	winctx->pin_win = txattr->pin_win;
+	winctx->rej_no_credit = txattr->rej_no_credit;
+	winctx->rsvd_txbuf_enable = txattr->rsvd_txbuf_enable;
+
+	winctx->rx_wcred_mode = txattr->rx_wcred_mode;
+	winctx->tx_wcred_mode = txattr->tx_wcred_mode;
+	winctx->rx_word_mode = txattr->rx_win_ord_mode;
+	winctx->tx_word_mode = txattr->tx_win_ord_mode;
+	winctx->rsvd_txbuf_count = txattr->rsvd_txbuf_count;
+
+	winctx->intr_disable = true;
+	if (winctx->nx_win)
+		winctx->data_stamp = true;
+
+	winctx->lpid = txattr->lpid;
+	winctx->pidr = txattr->pidr;
+	winctx->rx_win_id = txwin->rxwin->winid;
+	/*
+	 * IRQ and fault window setup is successful. Set fault window
+	 * for the send window so that ready to handle faults.
+	 */
+	if (txwin->vinst->virq)
+		winctx->fault_win_id = txwin->vinst->fault_win->winid;
+
+	winctx->dma_type = VAS_DMA_TYPE_INJECT;
+	winctx->tc_mode = txattr->tc_mode;
+	winctx->min_scope = VAS_SCOPE_LOCAL;
+	winctx->max_scope = VAS_SCOPE_VECTORED_GROUP;
+	if (txwin->vinst->virq)
+		winctx->irq_port = txwin->vinst->irq_port;
+
+	winctx->pswid = txattr->pswid ? txattr->pswid :
+			encode_pswid(txwin->vinst->vas_id, txwin->winid);
+}
+
+static bool tx_win_args_valid(enum vas_cop_type cop,
+			struct vas_tx_win_attr *attr)
+{
+	if (attr->tc_mode != VAS_THRESH_DISABLED)
+		return false;
+
+	if (cop > VAS_COP_TYPE_MAX)
+		return false;
+
+	if (attr->wcreds_max > VAS_TX_WCREDS_MAX)
+		return false;
+
+	if (attr->user_win) {
+		if (attr->rsvd_txbuf_count)
+			return false;
+
+		if (cop != VAS_COP_TYPE_FTW && cop != VAS_COP_TYPE_GZIP &&
+			cop != VAS_COP_TYPE_GZIP_HIPRI)
+			return false;
+	}
+
+	return true;
+}
+
+struct vas_window *vas_tx_win_open(int vasid, enum vas_cop_type cop,
+			struct vas_tx_win_attr *attr)
+{
+	int rc;
+	struct vas_window *txwin;
+	struct vas_window *rxwin;
+	struct vas_winctx winctx;
+	struct vas_instance *vinst;
+
+	trace_vas_tx_win_open(current, vasid, cop, attr);
+
+	if (!tx_win_args_valid(cop, attr))
+		return ERR_PTR(-EINVAL);
+
+	/*
+	 * If caller did not specify a vasid but specified the PSWID of a
+	 * receive window (applicable only to FTW windows), use the vasid
+	 * from that receive window.
+	 */
+	if (vasid == -1 && attr->pswid)
+		decode_pswid(attr->pswid, &vasid, NULL);
+
+	vinst = find_vas_instance(vasid);
+	if (!vinst) {
+		pr_devel("vasid %d not found!\n", vasid);
+		return ERR_PTR(-EINVAL);
+	}
+
+	rxwin = get_vinst_rxwin(vinst, cop, attr->pswid);
+	if (IS_ERR(rxwin)) {
+		pr_devel("No RxWin for vasid %d, cop %d\n", vasid, cop);
+		return rxwin;
+	}
+
+	txwin = vas_window_alloc(vinst);
+	if (IS_ERR(txwin)) {
+		rc = PTR_ERR(txwin);
+		goto put_rxwin;
+	}
+
+	txwin->cop = cop;
+	txwin->tx_win = 1;
+	txwin->rxwin = rxwin;
+	txwin->nx_win = txwin->rxwin->nx_win;
+	txwin->user_win = attr->user_win;
+	txwin->wcreds_max = attr->wcreds_max ?: VAS_WCREDS_DEFAULT;
+
+	init_winctx_for_txwin(txwin, attr, &winctx);
+
+	init_winctx_regs(txwin, &winctx);
+
+	/*
+	 * If its a kernel send window, map the window address into the
+	 * kernel's address space. For user windows, user must issue an
+	 * mmap() to map the window into their address space.
+	 *
+	 * NOTE: If kernel ever resubmits a user CRB after handling a page
+	 *	 fault, we will need to map this into kernel as well.
+	 */
+	if (!txwin->user_win) {
+		txwin->paste_kaddr = map_paste_region(txwin);
+		if (IS_ERR(txwin->paste_kaddr)) {
+			rc = PTR_ERR(txwin->paste_kaddr);
+			goto free_window;
+		}
+	} else {
+		/*
+		 * Interrupt hanlder or fault window setup failed. Means
+		 * NX can not generate fault for page fault. So not
+		 * opening for user space tx window.
+		 */
+		if (!vinst->virq) {
+			rc = -ENODEV;
+			goto free_window;
+		}
+
+		/*
+		 * Window opened by a child thread may not be closed when
+		 * it exits. So take reference to its pid and release it
+		 * when the window is free by parent thread.
+		 * Acquire a reference to the task's pid to make sure
+		 * pid will not be re-used - needed only for multithread
+		 * applications.
+		 */
+		txwin->pid = get_task_pid(current, PIDTYPE_PID);
+		/*
+		 * Acquire a reference to the task's mm.
+		 */
+		txwin->mm = get_task_mm(current);
+
+		if (!txwin->mm) {
+			put_pid(txwin->pid);
+			pr_err("VAS: pid(%d): mm_struct is not found\n",
+					current->pid);
+			rc = -EPERM;
+			goto free_window;
+		}
+
+		mmgrab(txwin->mm);
+		mmput(txwin->mm);
+		mm_context_add_vas_window(txwin->mm);
+		/*
+		 * Process closes window during exit. In the case of
+		 * multithread application, the child thread can open
+		 * window and can exit without closing it. so takes tgid
+		 * reference until window closed to make sure tgid is not
+		 * reused.
+		 */
+		txwin->tgid = find_get_pid(task_tgid_vnr(current));
+		/*
+		 * Even a process that has no foreign real address mapping can
+		 * use an unpaired COPY instruction (to no real effect). Issue
+		 * CP_ABORT to clear any pending COPY and prevent a covert
+		 * channel.
+		 *
+		 * __switch_to() will issue CP_ABORT on future context switches
+		 * if process / thread has any open VAS window (Use
+		 * current->mm->context.vas_windows).
+		 */
+		asm volatile(PPC_CP_ABORT);
+	}
+
+	set_vinst_win(vinst, txwin);
+
+	return txwin;
+
+free_window:
+	vas_window_free(txwin);
+
+put_rxwin:
+	put_rx_win(rxwin);
+	return ERR_PTR(rc);
+
+}
+EXPORT_SYMBOL_GPL(vas_tx_win_open);
+
+int vas_copy_crb(void *crb, int offset)
+{
+	return vas_copy(crb, offset);
+}
+EXPORT_SYMBOL_GPL(vas_copy_crb);
+
+#define RMA_LSMP_REPORT_ENABLE PPC_BIT(53)
+int vas_paste_crb(struct vas_window *txwin, int offset, bool re)
+{
+	int rc;
+	void *addr;
+	uint64_t val;
+
+	trace_vas_paste_crb(current, txwin);
+
+	/*
+	 * Only NX windows are supported for now and hardware assumes
+	 * report-enable flag is set for NX windows. Ensure software
+	 * complies too.
+	 */
+	WARN_ON_ONCE(txwin->nx_win && !re);
+
+	addr = txwin->paste_kaddr;
+	if (re) {
+		/*
+		 * Set the REPORT_ENABLE bit (equivalent to writing
+		 * to 1K offset of the paste address)
+		 */
+		val = SET_FIELD(RMA_LSMP_REPORT_ENABLE, 0ULL, 1);
+		addr += val;
+	}
+
+	/*
+	 * Map the raw CR value from vas_paste() to an error code (there
+	 * is just pass or fail for now though).
+	 */
+	rc = vas_paste(addr, offset);
+	if (rc == 2)
+		rc = 0;
+	else
+		rc = -EINVAL;
+
+	pr_debug("Txwin #%d: Msg count %llu\n", txwin->winid,
+			read_hvwc_reg(txwin, VREG(LRFIFO_PUSH)));
+
+	return rc;
+}
+EXPORT_SYMBOL_GPL(vas_paste_crb);
+
+/*
+ * If credit checking is enabled for this window, poll for the return
+ * of window credits (i.e for NX engines to process any outstanding CRBs).
+ * Since NX-842 waits for the CRBs to be processed before closing the
+ * window, we should not have to wait for too long.
+ *
+ * TODO: We retry in 10ms intervals now. We could/should probably peek at
+ *	the VAS_LRFIFO_PUSH_OFFSET register to get an estimate of pending
+ *	CRBs on the FIFO and compute the delay dynamically on each retry.
+ *	But that is not really needed until we support NX-GZIP access from
+ *	user space. (NX-842 driver waits for CSB and Fast thread-wakeup
+ *	doesn't use credit checking).
+ */
+static void poll_window_credits(struct vas_window *window)
+{
+	u64 val;
+	int creds, mode;
+	int count = 0;
+
+	val = read_hvwc_reg(window, VREG(WINCTL));
+	if (window->tx_win)
+		mode = GET_FIELD(VAS_WINCTL_TX_WCRED_MODE, val);
+	else
+		mode = GET_FIELD(VAS_WINCTL_RX_WCRED_MODE, val);
+
+	if (!mode)
+		return;
+retry:
+	if (window->tx_win) {
+		val = read_hvwc_reg(window, VREG(TX_WCRED));
+		creds = GET_FIELD(VAS_TX_WCRED, val);
+	} else {
+		val = read_hvwc_reg(window, VREG(LRX_WCRED));
+		creds = GET_FIELD(VAS_LRX_WCRED, val);
+	}
+
+	/*
+	 * Takes around few milliseconds to complete all pending requests
+	 * and return credits.
+	 * TODO: Scan fault FIFO and invalidate CRBs points to this window
+	 *       and issue CRB Kill to stop all pending requests. Need only
+	 *       if there is a bug in NX or fault handling in kernel.
+	 */
+	if (creds < window->wcreds_max) {
+		val = 0;
+		set_current_state(TASK_UNINTERRUPTIBLE);
+		schedule_timeout(msecs_to_jiffies(10));
+		count++;
+		/*
+		 * Process can not close send window until all credits are
+		 * returned.
+		 */
+		if (!(count % 1000))
+			pr_warn_ratelimited("VAS: pid %d stuck. Waiting for credits returned for Window(%d). creds %d, Retries %d\n",
+				vas_window_pid(window), window->winid,
+				creds, count);
+
+		goto retry;
+	}
+}
+
+/*
+ * Wait for the window to go to "not-busy" state. It should only take a
+ * short time to queue a CRB, so window should not be busy for too long.
+ * Trying 5ms intervals.
+ */
+static void poll_window_busy_state(struct vas_window *window)
+{
+	int busy;
+	u64 val;
+	int count = 0;
+
+retry:
+	val = read_hvwc_reg(window, VREG(WIN_STATUS));
+	busy = GET_FIELD(VAS_WIN_BUSY, val);
+	if (busy) {
+		val = 0;
+		set_current_state(TASK_UNINTERRUPTIBLE);
+		schedule_timeout(msecs_to_jiffies(10));
+		count++;
+		/*
+		 * Takes around few milliseconds to process all pending
+		 * requests.
+		 */
+		if (!(count % 1000))
+			pr_warn_ratelimited("VAS: pid %d stuck. Window (ID=%d) is in busy state. Retries %d\n",
+				vas_window_pid(window), window->winid, count);
+
+		goto retry;
+	}
+}
+
+/*
+ * Have the hardware cast a window out of cache and wait for it to
+ * be completed.
+ *
+ * NOTE: It can take a relatively long time to cast the window context
+ *	out of the cache. It is not strictly necessary to cast out if:
+ *
+ *	- we clear the "Pin Window" bit (so hardware is free to evict)
+ *
+ *	- we re-initialize the window context when it is reassigned.
+ *
+ *	We do the former in vas_win_close() and latter in vas_win_open().
+ *	So, ignoring the cast-out for now. We can add it as needed. If
+ *	casting out becomes necessary we should consider offloading the
+ *	job to a worker thread, so the window close can proceed quickly.
+ */
+static void poll_window_castout(struct vas_window *window)
+{
+	/* stub for now */
+}
+
+/*
+ * Unpin and close a window so no new requests are accepted and the
+ * hardware can evict this window from cache if necessary.
+ */
+static void unpin_close_window(struct vas_window *window)
+{
+	u64 val;
+
+	val = read_hvwc_reg(window, VREG(WINCTL));
+	val = SET_FIELD(VAS_WINCTL_PIN, val, 0);
+	val = SET_FIELD(VAS_WINCTL_OPEN, val, 0);
+	write_hvwc_reg(window, VREG(WINCTL), val);
+}
+
+/*
+ * Close a window.
+ *
+ * See Section 1.12.1 of VAS workbook v1.05 for details on closing window:
+ *	- Disable new paste operations (unmap paste address)
+ *	- Poll for the "Window Busy" bit to be cleared
+ *	- Clear the Open/Enable bit for the Window.
+ *	- Poll for return of window Credits (implies FIFO empty for Rx win?)
+ *	- Unpin and cast window context out of cache
+ *
+ * Besides the hardware, kernel has some bookkeeping of course.
+ */
+int vas_win_close(struct vas_window *window)
+{
+	if (!window)
+		return 0;
+
+	if (!window->tx_win && atomic_read(&window->num_txwins) != 0) {
+		pr_devel("Attempting to close an active Rx window!\n");
+		WARN_ON_ONCE(1);
+		return -EBUSY;
+	}
+
+	unmap_paste_region(window);
+
+	poll_window_busy_state(window);
+
+	unpin_close_window(window);
+
+	poll_window_credits(window);
+
+	clear_vinst_win(window);
+
+	poll_window_castout(window);
+
+	/* if send window, drop reference to matching receive window */
+	if (window->tx_win) {
+		if (window->user_win) {
+			/* Drop references to pid. tgid and mm */
+			put_pid(window->pid);
+			put_pid(window->tgid);
+			if (window->mm) {
+				mm_context_remove_vas_window(window->mm);
+				mmdrop(window->mm);
+			}
+		}
+		put_rx_win(window->rxwin);
+	}
+
+	vas_window_free(window);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(vas_win_close);
+
+/*
+ * Return credit for the given window.
+ * Send windows and fault window uses credit mechanism as follows:
+ *
+ * Send windows:
+ * - The default number of credits available for each send window is
+ *   1024. It means 1024 requests can be issued asynchronously at the
+ *   same time. If the credit is not available, that request will be
+ *   returned with RMA_Busy.
+ * - One credit is taken when NX request is issued.
+ * - This credit is returned after NX processed that request.
+ * - If NX encounters translation error, kernel will return the
+ *   credit on the specific send window after processing the fault CRB.
+ *
+ * Fault window:
+ * - The total number credits available is FIFO_SIZE/CRB_SIZE.
+ *   Means 4MB/128 in the current implementation. If credit is not
+ *   available, RMA_Reject is returned.
+ * - A credit is taken when NX pastes CRB in fault FIFO.
+ * - The kernel with return credit on fault window after reading entry
+ *   from fault FIFO.
+ */
+void vas_return_credit(struct vas_window *window, bool tx)
+{
+	uint64_t val;
+
+	val = 0ULL;
+	if (tx) { /* send window */
+		val = SET_FIELD(VAS_TX_WCRED, val, 1);
+		write_hvwc_reg(window, VREG(TX_WCRED_ADDER), val);
+	} else {
+		val = SET_FIELD(VAS_LRX_WCRED, val, 1);
+		write_hvwc_reg(window, VREG(LRX_WCRED_ADDER), val);
+	}
+}
+
+struct vas_window *vas_pswid_to_window(struct vas_instance *vinst,
+		uint32_t pswid)
+{
+	struct vas_window *window;
+	int winid;
+
+	if (!pswid) {
+		pr_devel("%s: called for pswid 0!\n", __func__);
+		return ERR_PTR(-ESRCH);
+	}
+
+	decode_pswid(pswid, NULL, &winid);
+
+	if (winid >= VAS_WINDOWS_PER_CHIP)
+		return ERR_PTR(-ESRCH);
+
+	/*
+	 * If application closes the window before the hardware
+	 * returns the fault CRB, we should wait in vas_win_close()
+	 * for the pending requests. so the window must be active
+	 * and the process alive.
+	 *
+	 * If its a kernel process, we should not get any faults and
+	 * should not get here.
+	 */
+	window = vinst->windows[winid];
+
+	if (!window) {
+		pr_err("PSWID decode: Could not find window for winid %d pswid %d vinst 0x%p\n",
+			winid, pswid, vinst);
+		return NULL;
+	}
+
+	/*
+	 * Do some sanity checks on the decoded window.  Window should be
+	 * NX GZIP user send window. FTW windows should not incur faults
+	 * since their CRBs are ignored (not queued on FIFO or processed
+	 * by NX).
+	 */
+	if (!window->tx_win || !window->user_win || !window->nx_win ||
+			window->cop == VAS_COP_TYPE_FAULT ||
+			window->cop == VAS_COP_TYPE_FTW) {
+		pr_err("PSWID decode: id %d, tx %d, user %d, nx %d, cop %d\n",
+			winid, window->tx_win, window->user_win,
+			window->nx_win, window->cop);
+		WARN_ON(1);
+	}
+
+	return window;
+}