drivers/misc/cxl/fault.c - linux - Git at Google

 /*
  * Copyright 2014 IBM Corp.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
  * as published by the Free Software Foundation; either version
  * 2 of the License, or (at your option) any later version.
  */

 #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 (!atomic_inc_not_zero(&ctx->mm->mm_users))
 		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 void cxl_prefault_one(struct cxl_context *ctx, u64 ea)
 {
 	struct mm_struct *mm;

 	mm = get_mem_context(ctx);
 	if (mm == NULL) {
 		pr_devel("cxl_prefault_one unable to get mm %i\n",
 			 pid_nr(ctx->pid));
 		return;
 	}

 	cxl_fault_segment(ctx, mm, ea);

 	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)
 {
 	u64 ea, last_esid = 0;
 	struct copro_slb slb;
 	struct vm_area_struct *vma;
 	int rc;
 	struct mm_struct *mm;

 	mm = get_mem_context(ctx);
 	if (mm == NULL) {
 		pr_devel("cxl_prefault_vm unable to get mm %i\n",
 			 pid_nr(ctx->pid));
 		return;
 	}

 	down_read(&mm->mmap_sem);
 	for (vma = mm->mmap; vma; vma = vma->vm_next) {
 		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;
 		}
 	}
 	up_read(&mm->mmap_sem);

 	mmput(mm);
 }

 void cxl_prefault(struct cxl_context *ctx, u64 wed)
 {
 	switch (ctx->afu->prefault_mode) {
 	case CXL_PREFAULT_WED:
 		cxl_prefault_one(ctx, wed);
 		break;
 	case CXL_PREFAULT_ALL:
 		cxl_prefault_vma(ctx);
 		break;
 	default:
 		break;
 	}
 }
	/*
	* Copyright 2014 IBM Corp.
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License
	* as published by the Free Software Foundation; either version
	* 2 of the License, or (at your option) any later version.
	*/

	#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 (!atomic_inc_not_zero(&ctx->mm->mm_users))
	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 void cxl_prefault_one(struct cxl_context *ctx, u64 ea)
	{
	struct mm_struct *mm;

	mm = get_mem_context(ctx);
	if (mm == NULL) {
	pr_devel("cxl_prefault_one unable to get mm %i\n",
	pid_nr(ctx->pid));
	return;
	}

	cxl_fault_segment(ctx, mm, ea);

	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)
	{
	u64 ea, last_esid = 0;
	struct copro_slb slb;
	struct vm_area_struct *vma;
	int rc;
	struct mm_struct *mm;

	mm = get_mem_context(ctx);
	if (mm == NULL) {
	pr_devel("cxl_prefault_vm unable to get mm %i\n",
	pid_nr(ctx->pid));
	return;
	}

	down_read(&mm->mmap_sem);
	for (vma = mm->mmap; vma; vma = vma->vm_next) {
	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;
	}
	}
	up_read(&mm->mmap_sem);

	mmput(mm);
	}

	void cxl_prefault(struct cxl_context *ctx, u64 wed)
	{
	switch (ctx->afu->prefault_mode) {
	case CXL_PREFAULT_WED:
	cxl_prefault_one(ctx, wed);
	break;
	case CXL_PREFAULT_ALL:
	cxl_prefault_vma(ctx);
	break;
	default:
	break;
	}
	}