3 files changed, 651 insertions, 0 deletions

diff --git a/arch/powerpc/platforms/book3s/Kconfig b/arch/powerpc/platforms/book3s/Kconfig
new file mode 100644
index 000000000..34c931592
--- /dev/null
+++ b/arch/powerpc/platforms/book3s/Kconfig
@@ -0,0 +1,15 @@
+# SPDX-License-Identifier: GPL-2.0
+config PPC_VAS
+	bool "IBM Virtual Accelerator Switchboard (VAS)"
+	depends on (PPC_POWERNV || PPC_PSERIES) && PPC_64K_PAGES
+	default y
+	help
+	  This enables support for IBM Virtual Accelerator Switchboard (VAS).
+
+	  VAS devices are found in POWER9-based and later systems, they
+	  provide access to accelerator coprocessors such as NX-GZIP and
+	  NX-842. This config allows the kernel to use NX-842 accelerators,
+	  and user-mode APIs for the NX-GZIP accelerator on POWER9 PowerNV
+	  and POWER10 PowerVM platforms.
+
+	  If unsure, say "N".
diff --git a/arch/powerpc/platforms/book3s/Makefile b/arch/powerpc/platforms/book3s/Makefile
new file mode 100644
index 000000000..e790f1910
--- /dev/null
+++ b/arch/powerpc/platforms/book3s/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_PPC_VAS)	+= vas-api.o
diff --git a/arch/powerpc/platforms/book3s/vas-api.c b/arch/powerpc/platforms/book3s/vas-api.c
new file mode 100644
index 000000000..92e60cb31
--- /dev/null
+++ b/arch/powerpc/platforms/book3s/vas-api.c
@@ -0,0 +1,634 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * VAS user space API for its accelerators (Only NX-GZIP is supported now)
+ * Copyright (C) 2019 Haren Myneni, IBM Corp
+ */
+
+#define pr_fmt(fmt)	"vas-api: " fmt
+
+#include <linux/kernel.h>
+#include <linux/device.h>
+#include <linux/cdev.h>
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <linux/kthread.h>
+#include <linux/sched/signal.h>
+#include <linux/mmu_context.h>
+#include <linux/io.h>
+#include <asm/vas.h>
+#include <uapi/asm/vas-api.h>
+
+/*
+ * The driver creates the device node that can be used as follows:
+ * For NX-GZIP
+ *
+ *	fd = open("/dev/crypto/nx-gzip", O_RDWR);
+ *	rc = ioctl(fd, VAS_TX_WIN_OPEN, &attr);
+ *	paste_addr = mmap(NULL, PAGE_SIZE, prot, MAP_SHARED, fd, 0ULL).
+ *	vas_copy(&crb, 0, 1);
+ *	vas_paste(paste_addr, 0, 1);
+ *	close(fd) or exit process to close window.
+ *
+ * where "vas_copy" and "vas_paste" are defined in copy-paste.h.
+ * copy/paste returns to the user space directly. So refer NX hardware
+ * documentation for exact copy/paste usage and completion / error
+ * conditions.
+ */
+
+/*
+ * Wrapper object for the nx-gzip device - there is just one instance of
+ * this node for the whole system.
+ */
+static struct coproc_dev {
+	struct cdev cdev;
+	struct device *device;
+	char *name;
+	dev_t devt;
+	struct class *class;
+	enum vas_cop_type cop_type;
+	const struct vas_user_win_ops *vops;
+} coproc_device;
+
+struct coproc_instance {
+	struct coproc_dev *coproc;
+	struct vas_window *txwin;
+};
+
+static char *coproc_devnode(struct device *dev, umode_t *mode)
+{
+	return kasprintf(GFP_KERNEL, "crypto/%s", dev_name(dev));
+}
+
+/*
+ * Take reference to pid and mm
+ */
+int get_vas_user_win_ref(struct vas_user_win_ref *task_ref)
+{
+	/*
+	 * 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.
+	 */
+	task_ref->pid = get_task_pid(current, PIDTYPE_PID);
+	/*
+	 * Acquire a reference to the task's mm.
+	 */
+	task_ref->mm = get_task_mm(current);
+	if (!task_ref->mm) {
+		put_pid(task_ref->pid);
+		pr_err("pid(%d): mm_struct is not found\n",
+				current->pid);
+		return -EPERM;
+	}
+
+	mmgrab(task_ref->mm);
+	mmput(task_ref->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.
+	 */
+	task_ref->tgid = find_get_pid(task_tgid_vnr(current));
+
+	return 0;
+}
+
+/*
+ * Successful return must release the task reference with
+ * put_task_struct
+ */
+static bool ref_get_pid_and_task(struct vas_user_win_ref *task_ref,
+			  struct task_struct **tskp, struct pid **pidp)
+{
+	struct task_struct *tsk;
+	struct pid *pid;
+
+	pid = task_ref->pid;
+	tsk = get_pid_task(pid, PIDTYPE_PID);
+	if (!tsk) {
+		pid = task_ref->tgid;
+		tsk = get_pid_task(pid, PIDTYPE_PID);
+		/*
+		 * Parent thread (tgid) will be closing window when it
+		 * exits. So should not get here.
+		 */
+		if (WARN_ON_ONCE(!tsk))
+			return false;
+	}
+
+	/* Return if the task is exiting. */
+	if (tsk->flags & PF_EXITING) {
+		put_task_struct(tsk);
+		return false;
+	}
+
+	*tskp = tsk;
+	*pidp = pid;
+
+	return true;
+}
+
+/*
+ * Update the CSB to indicate a translation error.
+ *
+ * User space will be polling on CSB after the request is issued.
+ * If NX can handle the request without any issues, it updates CSB.
+ * Whereas if NX encounters page fault, the kernel will handle the
+ * fault and update CSB with translation error.
+ *
+ * If we are unable to update the CSB means copy_to_user failed due to
+ * invalid csb_addr, send a signal to the process.
+ */
+void vas_update_csb(struct coprocessor_request_block *crb,
+		    struct vas_user_win_ref *task_ref)
+{
+	struct coprocessor_status_block csb;
+	struct kernel_siginfo info;
+	struct task_struct *tsk;
+	void __user *csb_addr;
+	struct pid *pid;
+	int rc;
+
+	/*
+	 * NX user space windows can not be opened for task->mm=NULL
+	 * and faults will not be generated for kernel requests.
+	 */
+	if (WARN_ON_ONCE(!task_ref->mm))
+		return;
+
+	csb_addr = (void __user *)be64_to_cpu(crb->csb_addr);
+
+	memset(&csb, 0, sizeof(csb));
+	csb.cc = CSB_CC_FAULT_ADDRESS;
+	csb.ce = CSB_CE_TERMINATION;
+	csb.cs = 0;
+	csb.count = 0;
+
+	/*
+	 * NX operates and returns in BE format as defined CRB struct.
+	 * So saves fault_storage_addr in BE as NX pastes in FIFO and
+	 * expects user space to convert to CPU format.
+	 */
+	csb.address = crb->stamp.nx.fault_storage_addr;
+	csb.flags = 0;
+
+	/*
+	 * Process closes send window after all pending NX requests are
+	 * completed. In multi-thread applications, a child thread can
+	 * open a window and can exit without closing it. May be some
+	 * requests are pending or this window can be used by other
+	 * threads later. We should handle faults if NX encounters
+	 * pages faults on these requests. Update CSB with translation
+	 * error and fault address. If csb_addr passed by user space is
+	 * invalid, send SEGV signal to pid saved in window. If the
+	 * child thread is not running, send the signal to tgid.
+	 * Parent thread (tgid) will close this window upon its exit.
+	 *
+	 * pid and mm references are taken when window is opened by
+	 * process (pid). So tgid is used only when child thread opens
+	 * a window and exits without closing it.
+	 */
+
+	if (!ref_get_pid_and_task(task_ref, &tsk, &pid))
+		return;
+
+	kthread_use_mm(task_ref->mm);
+	rc = copy_to_user(csb_addr, &csb, sizeof(csb));
+	/*
+	 * User space polls on csb.flags (first byte). So add barrier
+	 * then copy first byte with csb flags update.
+	 */
+	if (!rc) {
+		csb.flags = CSB_V;
+		/* Make sure update to csb.flags is visible now */
+		smp_mb();
+		rc = copy_to_user(csb_addr, &csb, sizeof(u8));
+	}
+	kthread_unuse_mm(task_ref->mm);
+	put_task_struct(tsk);
+
+	/* Success */
+	if (!rc)
+		return;
+
+
+	pr_debug("Invalid CSB address 0x%p signalling pid(%d)\n",
+			csb_addr, pid_vnr(pid));
+
+	clear_siginfo(&info);
+	info.si_signo = SIGSEGV;
+	info.si_errno = EFAULT;
+	info.si_code = SEGV_MAPERR;
+	info.si_addr = csb_addr;
+	/*
+	 * process will be polling on csb.flags after request is sent to
+	 * NX. So generally CSB update should not fail except when an
+	 * application passes invalid csb_addr. So an error message will
+	 * be displayed and leave it to user space whether to ignore or
+	 * handle this signal.
+	 */
+	rcu_read_lock();
+	rc = kill_pid_info(SIGSEGV, &info, pid);
+	rcu_read_unlock();
+
+	pr_devel("pid %d kill_proc_info() rc %d\n", pid_vnr(pid), rc);
+}
+
+void vas_dump_crb(struct coprocessor_request_block *crb)
+{
+	struct data_descriptor_entry *dde;
+	struct nx_fault_stamp *nx;
+
+	dde = &crb->source;
+	pr_devel("SrcDDE: addr 0x%llx, len %d, count %d, idx %d, flags %d\n",
+		be64_to_cpu(dde->address), be32_to_cpu(dde->length),
+		dde->count, dde->index, dde->flags);
+
+	dde = &crb->target;
+	pr_devel("TgtDDE: addr 0x%llx, len %d, count %d, idx %d, flags %d\n",
+		be64_to_cpu(dde->address), be32_to_cpu(dde->length),
+		dde->count, dde->index, dde->flags);
+
+	nx = &crb->stamp.nx;
+	pr_devel("NX Stamp: PSWID 0x%x, FSA 0x%llx, flags 0x%x, FS 0x%x\n",
+		be32_to_cpu(nx->pswid),
+		be64_to_cpu(crb->stamp.nx.fault_storage_addr),
+		nx->flags, nx->fault_status);
+}
+
+static int coproc_open(struct inode *inode, struct file *fp)
+{
+	struct coproc_instance *cp_inst;
+
+	cp_inst = kzalloc(sizeof(*cp_inst), GFP_KERNEL);
+	if (!cp_inst)
+		return -ENOMEM;
+
+	cp_inst->coproc = container_of(inode->i_cdev, struct coproc_dev,
+					cdev);
+	fp->private_data = cp_inst;
+
+	return 0;
+}
+
+static int coproc_ioc_tx_win_open(struct file *fp, unsigned long arg)
+{
+	void __user *uptr = (void __user *)arg;
+	struct vas_tx_win_open_attr uattr;
+	struct coproc_instance *cp_inst;
+	struct vas_window *txwin;
+	int rc;
+
+	cp_inst = fp->private_data;
+
+	/*
+	 * One window for file descriptor
+	 */
+	if (cp_inst->txwin)
+		return -EEXIST;
+
+	rc = copy_from_user(&uattr, uptr, sizeof(uattr));
+	if (rc) {
+		pr_err("copy_from_user() returns %d\n", rc);
+		return -EFAULT;
+	}
+
+	if (uattr.version != 1) {
+		pr_err("Invalid window open API version\n");
+		return -EINVAL;
+	}
+
+	if (!cp_inst->coproc->vops || !cp_inst->coproc->vops->open_win) {
+		pr_err("VAS API is not registered\n");
+		return -EACCES;
+	}
+
+	txwin = cp_inst->coproc->vops->open_win(uattr.vas_id, uattr.flags,
+						cp_inst->coproc->cop_type);
+	if (IS_ERR(txwin)) {
+		pr_err_ratelimited("VAS window open failed rc=%ld\n",
+				PTR_ERR(txwin));
+		return PTR_ERR(txwin);
+	}
+
+	mutex_init(&txwin->task_ref.mmap_mutex);
+	cp_inst->txwin = txwin;
+
+	return 0;
+}
+
+static int coproc_release(struct inode *inode, struct file *fp)
+{
+	struct coproc_instance *cp_inst = fp->private_data;
+	int rc;
+
+	if (cp_inst->txwin) {
+		if (cp_inst->coproc->vops &&
+			cp_inst->coproc->vops->close_win) {
+			rc = cp_inst->coproc->vops->close_win(cp_inst->txwin);
+			if (rc)
+				return rc;
+		}
+		cp_inst->txwin = NULL;
+	}
+
+	kfree(cp_inst);
+	fp->private_data = NULL;
+
+	/*
+	 * We don't know here if user has other receive windows
+	 * open, so we can't really call clear_thread_tidr().
+	 * So, once the process calls set_thread_tidr(), the
+	 * TIDR value sticks around until process exits, resulting
+	 * in an extra copy in restore_sprs().
+	 */
+
+	return 0;
+}
+
+/*
+ * If the executed instruction that caused the fault was a paste, then
+ * clear regs CR0[EQ], advance NIP, and return 0. Else return error code.
+ */
+static int do_fail_paste(void)
+{
+	struct pt_regs *regs = current->thread.regs;
+	u32 instword;
+
+	if (WARN_ON_ONCE(!regs))
+		return -EINVAL;
+
+	if (WARN_ON_ONCE(!user_mode(regs)))
+		return -EINVAL;
+
+	/*
+	 * If we couldn't translate the instruction, the driver should
+	 * return success without handling the fault, it will be retried
+	 * or the instruction fetch will fault.
+	 */
+	if (get_user(instword, (u32 __user *)(regs->nip)))
+		return -EAGAIN;
+
+	/*
+	 * Not a paste instruction, driver may fail the fault.
+	 */
+	if ((instword & PPC_INST_PASTE_MASK) != PPC_INST_PASTE)
+		return -ENOENT;
+
+	regs->ccr &= ~0xe0000000;	/* Clear CR0[0-2] to fail paste */
+	regs_add_return_ip(regs, 4);	/* Emulate the paste */
+
+	return 0;
+}
+
+/*
+ * This fault handler is invoked when the core generates page fault on
+ * the paste address. Happens if the kernel closes window in hypervisor
+ * (on pseries) due to lost credit or the paste address is not mapped.
+ */
+static vm_fault_t vas_mmap_fault(struct vm_fault *vmf)
+{
+	struct vm_area_struct *vma = vmf->vma;
+	struct file *fp = vma->vm_file;
+	struct coproc_instance *cp_inst = fp->private_data;
+	struct vas_window *txwin;
+	vm_fault_t fault;
+	u64 paste_addr;
+	int ret;
+
+	/*
+	 * window is not opened. Shouldn't expect this error.
+	 */
+	if (!cp_inst || !cp_inst->txwin) {
+		pr_err("Unexpected fault on paste address with TX window closed\n");
+		return VM_FAULT_SIGBUS;
+	}
+
+	txwin = cp_inst->txwin;
+	/*
+	 * When the LPAR lost credits due to core removal or during
+	 * migration, invalidate the existing mapping for the current
+	 * paste addresses and set windows in-active (zap_page_range in
+	 * reconfig_close_windows()).
+	 * New mapping will be done later after migration or new credits
+	 * available. So continue to receive faults if the user space
+	 * issue NX request.
+	 */
+	if (txwin->task_ref.vma != vmf->vma) {
+		pr_err("No previous mapping with paste address\n");
+		return VM_FAULT_SIGBUS;
+	}
+
+	mutex_lock(&txwin->task_ref.mmap_mutex);
+	/*
+	 * The window may be inactive due to lost credit (Ex: core
+	 * removal with DLPAR). If the window is active again when
+	 * the credit is available, map the new paste address at the
+	 * window virtual address.
+	 */
+	if (txwin->status == VAS_WIN_ACTIVE) {
+		paste_addr = cp_inst->coproc->vops->paste_addr(txwin);
+		if (paste_addr) {
+			fault = vmf_insert_pfn(vma, vma->vm_start,
+					(paste_addr >> PAGE_SHIFT));
+			mutex_unlock(&txwin->task_ref.mmap_mutex);
+			return fault;
+		}
+	}
+	mutex_unlock(&txwin->task_ref.mmap_mutex);
+
+	/*
+	 * Received this fault due to closing the actual window.
+	 * It can happen during migration or lost credits.
+	 * Since no mapping, return the paste instruction failure
+	 * to the user space.
+	 */
+	ret = do_fail_paste();
+	/*
+	 * The user space can retry several times until success (needed
+	 * for migration) or should fallback to SW compression or
+	 * manage with the existing open windows if available.
+	 * Looking at sysfs interface, it can determine whether these
+	 * failures are coming during migration or core removal:
+	 * nr_used_credits > nr_total_credits when lost credits
+	 */
+	if (!ret || (ret == -EAGAIN))
+		return VM_FAULT_NOPAGE;
+
+	return VM_FAULT_SIGBUS;
+}
+
+static const struct vm_operations_struct vas_vm_ops = {
+	.fault = vas_mmap_fault,
+};
+
+static int coproc_mmap(struct file *fp, struct vm_area_struct *vma)
+{
+	struct coproc_instance *cp_inst = fp->private_data;
+	struct vas_window *txwin;
+	unsigned long pfn;
+	u64 paste_addr;
+	pgprot_t prot;
+	int rc;
+
+	txwin = cp_inst->txwin;
+
+	if ((vma->vm_end - vma->vm_start) > PAGE_SIZE) {
+		pr_debug("size 0x%zx, PAGE_SIZE 0x%zx\n",
+				(vma->vm_end - vma->vm_start), PAGE_SIZE);
+		return -EINVAL;
+	}
+
+	/* Ensure instance has an open send window */
+	if (!txwin) {
+		pr_err("No send window open?\n");
+		return -EINVAL;
+	}
+
+	if (!cp_inst->coproc->vops || !cp_inst->coproc->vops->paste_addr) {
+		pr_err("VAS API is not registered\n");
+		return -EACCES;
+	}
+
+	/*
+	 * The initial mmap is done after the window is opened
+	 * with ioctl. But before mmap(), this window can be closed in
+	 * the hypervisor due to lost credit (core removal on pseries).
+	 * So if the window is not active, return mmap() failure with
+	 * -EACCES and expects the user space reissue mmap() when it
+	 * is active again or open new window when the credit is available.
+	 * mmap_mutex protects the paste address mmap() with DLPAR
+	 * close/open event and allows mmap() only when the window is
+	 * active.
+	 */
+	mutex_lock(&txwin->task_ref.mmap_mutex);
+	if (txwin->status != VAS_WIN_ACTIVE) {
+		pr_err("Window is not active\n");
+		rc = -EACCES;
+		goto out;
+	}
+
+	paste_addr = cp_inst->coproc->vops->paste_addr(txwin);
+	if (!paste_addr) {
+		pr_err("Window paste address failed\n");
+		rc = -EINVAL;
+		goto out;
+	}
+
+	pfn = paste_addr >> PAGE_SHIFT;
+
+	/* flags, page_prot from cxl_mmap(), except we want cachable */
+	vma->vm_flags |= VM_IO | VM_PFNMAP;
+	vma->vm_page_prot = pgprot_cached(vma->vm_page_prot);
+
+	prot = __pgprot(pgprot_val(vma->vm_page_prot) | _PAGE_DIRTY);
+
+	rc = remap_pfn_range(vma, vma->vm_start, pfn + vma->vm_pgoff,
+			vma->vm_end - vma->vm_start, prot);
+
+	pr_devel("paste addr %llx at %lx, rc %d\n", paste_addr,
+			vma->vm_start, rc);
+
+	txwin->task_ref.vma = vma;
+	vma->vm_ops = &vas_vm_ops;
+
+out:
+	mutex_unlock(&txwin->task_ref.mmap_mutex);
+	return rc;
+}
+
+static long coproc_ioctl(struct file *fp, unsigned int cmd, unsigned long arg)
+{
+	switch (cmd) {
+	case VAS_TX_WIN_OPEN:
+		return coproc_ioc_tx_win_open(fp, arg);
+	default:
+		return -EINVAL;
+	}
+}
+
+static struct file_operations coproc_fops = {
+	.open = coproc_open,
+	.release = coproc_release,
+	.mmap = coproc_mmap,
+	.unlocked_ioctl = coproc_ioctl,
+};
+
+/*
+ * Supporting only nx-gzip coprocessor type now, but this API code
+ * extended to other coprocessor types later.
+ */
+int vas_register_coproc_api(struct module *mod, enum vas_cop_type cop_type,
+			    const char *name,
+			    const struct vas_user_win_ops *vops)
+{
+	int rc = -EINVAL;
+	dev_t devno;
+
+	rc = alloc_chrdev_region(&coproc_device.devt, 1, 1, name);
+	if (rc) {
+		pr_err("Unable to allocate coproc major number: %i\n", rc);
+		return rc;
+	}
+
+	pr_devel("%s device allocated, dev [%i,%i]\n", name,
+			MAJOR(coproc_device.devt), MINOR(coproc_device.devt));
+
+	coproc_device.class = class_create(mod, name);
+	if (IS_ERR(coproc_device.class)) {
+		rc = PTR_ERR(coproc_device.class);
+		pr_err("Unable to create %s class %d\n", name, rc);
+		goto err_class;
+	}
+	coproc_device.class->devnode = coproc_devnode;
+	coproc_device.cop_type = cop_type;
+	coproc_device.vops = vops;
+
+	coproc_fops.owner = mod;
+	cdev_init(&coproc_device.cdev, &coproc_fops);
+
+	devno = MKDEV(MAJOR(coproc_device.devt), 0);
+	rc = cdev_add(&coproc_device.cdev, devno, 1);
+	if (rc) {
+		pr_err("cdev_add() failed %d\n", rc);
+		goto err_cdev;
+	}
+
+	coproc_device.device = device_create(coproc_device.class, NULL,
+			devno, NULL, name, MINOR(devno));
+	if (IS_ERR(coproc_device.device)) {
+		rc = PTR_ERR(coproc_device.device);
+		pr_err("Unable to create coproc-%d %d\n", MINOR(devno), rc);
+		goto err;
+	}
+
+	pr_devel("Added dev [%d,%d]\n", MAJOR(devno), MINOR(devno));
+
+	return 0;
+
+err:
+	cdev_del(&coproc_device.cdev);
+err_cdev:
+	class_destroy(coproc_device.class);
+err_class:
+	unregister_chrdev_region(coproc_device.devt, 1);
+	return rc;
+}
+
+void vas_unregister_coproc_api(void)
+{
+	dev_t devno;
+
+	cdev_del(&coproc_device.cdev);
+	devno = MKDEV(MAJOR(coproc_device.devt), 0);
+	device_destroy(coproc_device.class, devno);
+
+	class_destroy(coproc_device.class);
+	unregister_chrdev_region(coproc_device.devt, 1);
+}