1 files changed, 341 insertions, 0 deletions
diff --git a/drivers/misc/cxl/fault.c b/drivers/misc/cxl/fault.c
new file mode 100644
index 000000000..2c64f55cf
--- /dev/null
+++ b/drivers/misc/cxl/fault.c
@@ -0,0 +1,341 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright 2014 IBM Corp.
+ */
+
+#include <linux/workqueue.h>
+#include <linux/sched/signal.h>
+#include <linux/sched/mm.h>
+#include <linux/pid.h>
+#include <linux/mm.h>
+#include <linux/moduleparam.h>
+
+#undef MODULE_PARAM_PREFIX
+#define MODULE_PARAM_PREFIX "cxl" "."
+#include <asm/current.h>
+#include <asm/copro.h>
+#include <asm/mmu.h>
+
+#include "cxl.h"
+#include "trace.h"
+
+static bool sste_matches(struct cxl_sste *sste, struct copro_slb *slb)
+{
+	return ((sste->vsid_data == cpu_to_be64(slb->vsid)) &&
+		(sste->esid_data == cpu_to_be64(slb->esid)));
+}
+
+/*
+ * This finds a free SSTE for the given SLB, or returns NULL if it's already in
+ * the segment table.
+ */
+static struct cxl_sste *find_free_sste(struct cxl_context *ctx,
+				       struct copro_slb *slb)
+{
+	struct cxl_sste *primary, *sste, *ret = NULL;
+	unsigned int mask = (ctx->sst_size >> 7) - 1; /* SSTP0[SegTableSize] */
+	unsigned int entry;
+	unsigned int hash;
+
+	if (slb->vsid & SLB_VSID_B_1T)
+		hash = (slb->esid >> SID_SHIFT_1T) & mask;
+	else /* 256M */
+		hash = (slb->esid >> SID_SHIFT) & mask;
+
+	primary = ctx->sstp + (hash << 3);
+
+	for (entry = 0, sste = primary; entry < 8; entry++, sste++) {
+		if (!ret && !(be64_to_cpu(sste->esid_data) & SLB_ESID_V))
+			ret = sste;
+		if (sste_matches(sste, slb))
+			return NULL;
+	}
+	if (ret)
+		return ret;
+
+	/* Nothing free, select an entry to cast out */
+	ret = primary + ctx->sst_lru;
+	ctx->sst_lru = (ctx->sst_lru + 1) & 0x7;
+
+	return ret;
+}
+
+static void cxl_load_segment(struct cxl_context *ctx, struct copro_slb *slb)
+{
+	/* mask is the group index, we search primary and secondary here. */
+	struct cxl_sste *sste;
+	unsigned long flags;
+
+	spin_lock_irqsave(&ctx->sste_lock, flags);
+	sste = find_free_sste(ctx, slb);
+	if (!sste)
+		goto out_unlock;
+
+	pr_devel("CXL Populating SST[%li]: %#llx %#llx\n",
+			sste - ctx->sstp, slb->vsid, slb->esid);
+	trace_cxl_ste_write(ctx, sste - ctx->sstp, slb->esid, slb->vsid);
+
+	sste->vsid_data = cpu_to_be64(slb->vsid);
+	sste->esid_data = cpu_to_be64(slb->esid);
+out_unlock:
+	spin_unlock_irqrestore(&ctx->sste_lock, flags);
+}
+
+static int cxl_fault_segment(struct cxl_context *ctx, struct mm_struct *mm,
+			     u64 ea)
+{
+	struct copro_slb slb = {0,0};
+	int rc;
+
+	if (!(rc = copro_calculate_slb(mm, ea, &slb))) {
+		cxl_load_segment(ctx, &slb);
+	}
+
+	return rc;
+}
+
+static void cxl_ack_ae(struct cxl_context *ctx)
+{
+	unsigned long flags;
+
+	cxl_ops->ack_irq(ctx, CXL_PSL_TFC_An_AE, 0);
+
+	spin_lock_irqsave(&ctx->lock, flags);
+	ctx->pending_fault = true;
+	ctx->fault_addr = ctx->dar;
+	ctx->fault_dsisr = ctx->dsisr;
+	spin_unlock_irqrestore(&ctx->lock, flags);
+
+	wake_up_all(&ctx->wq);
+}
+
+static int cxl_handle_segment_miss(struct cxl_context *ctx,
+				   struct mm_struct *mm, u64 ea)
+{
+	int rc;
+
+	pr_devel("CXL interrupt: Segment fault pe: %i ea: %#llx\n", ctx->pe, ea);
+	trace_cxl_ste_miss(ctx, ea);
+
+	if ((rc = cxl_fault_segment(ctx, mm, ea)))
+		cxl_ack_ae(ctx);
+	else {
+
+		mb(); /* Order seg table write to TFC MMIO write */
+		cxl_ops->ack_irq(ctx, CXL_PSL_TFC_An_R, 0);
+	}
+
+	return IRQ_HANDLED;
+}
+
+int cxl_handle_mm_fault(struct mm_struct *mm, u64 dsisr, u64 dar)
+{
+	vm_fault_t flt = 0;
+	int result;
+	unsigned long access, flags, inv_flags = 0;
+
+	/*
+	 * Add the fault handling cpu to task mm cpumask so that we
+	 * can do a safe lockless page table walk when inserting the
+	 * hash page table entry. This function get called with a
+	 * valid mm for user space addresses. Hence using the if (mm)
+	 * check is sufficient here.
+	 */
+	if (mm && !cpumask_test_cpu(smp_processor_id(), mm_cpumask(mm))) {
+		cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm));
+		/*
+		 * We need to make sure we walk the table only after
+		 * we update the cpumask. The other side of the barrier
+		 * is explained in serialize_against_pte_lookup()
+		 */
+		smp_mb();
+	}
+	if ((result = copro_handle_mm_fault(mm, dar, dsisr, &flt))) {
+		pr_devel("copro_handle_mm_fault failed: %#x\n", result);
+		return result;
+	}
+
+	if (!radix_enabled()) {
+		/*
+		 * update_mmu_cache() will not have loaded the hash since current->trap
+		 * is not a 0x400 or 0x300, so just call hash_page_mm() here.
+		 */
+		access = _PAGE_PRESENT | _PAGE_READ;
+		if (dsisr & CXL_PSL_DSISR_An_S)
+			access |= _PAGE_WRITE;
+
+		if (!mm && (get_region_id(dar) != USER_REGION_ID))
+			access |= _PAGE_PRIVILEGED;
+
+		if (dsisr & DSISR_NOHPTE)
+			inv_flags |= HPTE_NOHPTE_UPDATE;
+
+		local_irq_save(flags);
+		hash_page_mm(mm, dar, access, 0x300, inv_flags);
+		local_irq_restore(flags);
+	}
+	return 0;
+}
+
+static void cxl_handle_page_fault(struct cxl_context *ctx,
+				  struct mm_struct *mm,
+				  u64 dsisr, u64 dar)
+{
+	trace_cxl_pte_miss(ctx, dsisr, dar);
+
+	if (cxl_handle_mm_fault(mm, dsisr, dar)) {
+		cxl_ack_ae(ctx);
+	} else {
+		pr_devel("Page fault successfully handled for pe: %i!\n", ctx->pe);
+		cxl_ops->ack_irq(ctx, CXL_PSL_TFC_An_R, 0);
+	}
+}
+
+/*
+ * Returns the mm_struct corresponding to the context ctx.
+ * mm_users == 0, the context may be in the process of being closed.
+ */
+static struct mm_struct *get_mem_context(struct cxl_context *ctx)
+{
+	if (ctx->mm == NULL)
+		return NULL;
+
+	if (!mmget_not_zero(ctx->mm))
+		return NULL;
+
+	return ctx->mm;
+}
+
+static bool cxl_is_segment_miss(struct cxl_context *ctx, u64 dsisr)
+{
+	if ((cxl_is_power8() && (dsisr & CXL_PSL_DSISR_An_DS)))
+		return true;
+
+	return false;
+}
+
+static bool cxl_is_page_fault(struct cxl_context *ctx, u64 dsisr)
+{
+	if ((cxl_is_power8()) && (dsisr & CXL_PSL_DSISR_An_DM))
+		return true;
+
+	if (cxl_is_power9())
+		return true;
+
+	return false;
+}
+
+void cxl_handle_fault(struct work_struct *fault_work)
+{
+	struct cxl_context *ctx =
+		container_of(fault_work, struct cxl_context, fault_work);
+	u64 dsisr = ctx->dsisr;
+	u64 dar = ctx->dar;
+	struct mm_struct *mm = NULL;
+
+	if (cpu_has_feature(CPU_FTR_HVMODE)) {
+		if (cxl_p2n_read(ctx->afu, CXL_PSL_DSISR_An) != dsisr ||
+		    cxl_p2n_read(ctx->afu, CXL_PSL_DAR_An) != dar ||
+		    cxl_p2n_read(ctx->afu, CXL_PSL_PEHandle_An) != ctx->pe) {
+			/* Most likely explanation is harmless - a dedicated
+			 * process has detached and these were cleared by the
+			 * PSL purge, but warn about it just in case
+			 */
+			dev_notice(&ctx->afu->dev, "cxl_handle_fault: Translation fault regs changed\n");
+			return;
+		}
+	}
+
+	/* Early return if the context is being / has been detached */
+	if (ctx->status == CLOSED) {
+		cxl_ack_ae(ctx);
+		return;
+	}
+
+	pr_devel("CXL BOTTOM HALF handling fault for afu pe: %i. "
+		"DSISR: %#llx DAR: %#llx\n", ctx->pe, dsisr, dar);
+
+	if (!ctx->kernel) {
+
+		mm = get_mem_context(ctx);
+		if (mm == NULL) {
+			pr_devel("%s: unable to get mm for pe=%d pid=%i\n",
+				 __func__, ctx->pe, pid_nr(ctx->pid));
+			cxl_ack_ae(ctx);
+			return;
+		} else {
+			pr_devel("Handling page fault for pe=%d pid=%i\n",
+				 ctx->pe, pid_nr(ctx->pid));
+		}
+	}
+
+	if (cxl_is_segment_miss(ctx, dsisr))
+		cxl_handle_segment_miss(ctx, mm, dar);
+	else if (cxl_is_page_fault(ctx, dsisr))
+		cxl_handle_page_fault(ctx, mm, dsisr, dar);
+	else
+		WARN(1, "cxl_handle_fault has nothing to handle\n");
+
+	if (mm)
+		mmput(mm);
+}
+
+static u64 next_segment(u64 ea, u64 vsid)
+{
+	if (vsid & SLB_VSID_B_1T)
+		ea |= (1ULL << 40) - 1;
+	else
+		ea |= (1ULL << 28) - 1;
+
+	return ea + 1;
+}
+
+static void cxl_prefault_vma(struct cxl_context *ctx, struct mm_struct *mm)
+{
+	u64 ea, last_esid = 0;
+	struct copro_slb slb;
+	VMA_ITERATOR(vmi, mm, 0);
+	struct vm_area_struct *vma;
+	int rc;
+
+	mmap_read_lock(mm);
+	for_each_vma(vmi, vma) {
+		for (ea = vma->vm_start; ea < vma->vm_end;
+				ea = next_segment(ea, slb.vsid)) {
+			rc = copro_calculate_slb(mm, ea, &slb);
+			if (rc)
+				continue;
+
+			if (last_esid == slb.esid)
+				continue;
+
+			cxl_load_segment(ctx, &slb);
+			last_esid = slb.esid;
+		}
+	}
+	mmap_read_unlock(mm);
+}
+
+void cxl_prefault(struct cxl_context *ctx, u64 wed)
+{
+	struct mm_struct *mm = get_mem_context(ctx);
+
+	if (mm == NULL) {
+		pr_devel("cxl_prefault unable to get mm %i\n",
+			 pid_nr(ctx->pid));
+		return;
+	}
+
+	switch (ctx->afu->prefault_mode) {
+	case CXL_PREFAULT_WED:
+		cxl_fault_segment(ctx, mm, wed);
+		break;
+	case CXL_PREFAULT_ALL:
+		cxl_prefault_vma(ctx, mm);
+		break;
+	default:
+		break;
+	}
+
+	mmput(mm);
+}