From: Dominik Dingel <din...@linux.vnet.ibm.com>
In case of a fault retry exit sie64() with gmap_fault indication for the
running thread set. This makes it possible to handle async page faults
without the need for mm notifiers.
Based on a patch from Martin Schwidefsky.
Signed-off-by: Dominik Dingel <din...@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntrae...@de.ibm.com>
---
arch/s390/include/asm/pgtable.h | 2 ++
arch/s390/include/asm/processor.h | 1 +
arch/s390/kvm/kvm-s390.c | 28 +++++++++++++++++++++++-----
arch/s390/mm/fault.c | 26 ++++++++++++++++++++++----
4 files changed, 48 insertions(+), 9 deletions(-)
diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 9b60a36..18495d9 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -765,6 +765,7 @@ static inline void pgste_set_pte(pte_t *ptep, pte_t entry)
* @table: pointer to the page directory
* @asce: address space control element for gmap page table
* @crst_list: list of all crst tables used in the guest address space
+ * @pfault_enabled: defines if pfaults are applicable for the guest
*/
struct gmap {
struct list_head list;
@@ -773,6 +774,7 @@ struct gmap {
unsigned long asce;
void *private;
struct list_head crst_list;
+ bool pfault_enabled;
};
/**
diff --git a/arch/s390/include/asm/processor.h
b/arch/s390/include/asm/processor.h
index 0eb3750..bea6968 100644
--- a/arch/s390/include/asm/processor.h
+++ b/arch/s390/include/asm/processor.h
@@ -79,6 +79,7 @@ struct thread_struct {
unsigned long ksp; /* kernel stack pointer */
mm_segment_t mm_segment;
unsigned long gmap_addr; /* address of last gmap fault. */
+ unsigned int gmap_pfault; /* signal of a pending guest pfault */
struct per_regs per_user; /* User specified PER registers */
struct per_event per_event; /* Cause of the last PER trap */
unsigned long per_flags; /* Flags to control debug behavior */
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 30e2c9a..785e36e 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -255,6 +255,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
if (!kvm->arch.gmap)
goto out_nogmap;
kvm->arch.gmap->private = kvm;
+ kvm->arch.gmap->pfault_enabled = 0;
}
kvm->arch.css_support = 0;
@@ -690,6 +691,17 @@ static int kvm_s390_handle_requests(struct kvm_vcpu *vcpu)
return 0;
}
+static long kvm_arch_fault_in_sync(struct kvm_vcpu *vcpu)
+{
+ long rc;
+ hva_t fault = gmap_fault(current->thread.gmap_addr, vcpu->arch.gmap);
+ struct mm_struct *mm = current->mm;
+ down_read(&mm->mmap_sem);
+ rc = get_user_pages(current, mm, fault, 1, 1, 0, NULL, NULL);
+ up_read(&mm->mmap_sem);
+ return rc;
+}
+
static int vcpu_pre_run(struct kvm_vcpu *vcpu)
{
int rc, cpuflags;
@@ -719,7 +731,7 @@ static int vcpu_pre_run(struct kvm_vcpu *vcpu)
static int vcpu_post_run(struct kvm_vcpu *vcpu, int exit_reason)
{
- int rc;
+ int rc = -1;
VCPU_EVENT(vcpu, 6, "exit sie icptcode %d",
vcpu->arch.sie_block->icptcode);
@@ -730,13 +742,19 @@ static int vcpu_post_run(struct kvm_vcpu *vcpu, int
exit_reason)
} else {
if (kvm_is_ucontrol(vcpu->kvm)) {
rc = SIE_INTERCEPT_UCONTROL;
- } else {
- VCPU_EVENT(vcpu, 3, "%s", "fault in sie instruction");
- trace_kvm_s390_sie_fault(vcpu);
- rc = kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
+ } else if (current->thread.gmap_pfault) {
+ current->thread.gmap_pfault = 0;
+ if (kvm_arch_fault_in_sync(vcpu) >= 0)
+ rc = 0;
}
}
+ if (rc == -1) {
+ VCPU_EVENT(vcpu, 3, "%s", "fault in sie instruction");
+ trace_kvm_s390_sie_fault(vcpu);
+ rc = kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
+ }
+
memcpy(&vcpu->run->s.regs.gprs[14], &vcpu->arch.sie_block->gg14, 16);
if (rc == 0) {
diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index fc66792..7505552 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -50,6 +50,7 @@
#define VM_FAULT_BADMAP 0x020000
#define VM_FAULT_BADACCESS 0x040000
#define VM_FAULT_SIGNAL 0x080000
+#define VM_FAULT_PFAULT 0x100000
static unsigned long store_indication __read_mostly;
@@ -232,6 +233,7 @@ static noinline void do_fault_error(struct pt_regs *regs,
int fault)
return;
}
case VM_FAULT_BADCONTEXT:
+ case VM_FAULT_PFAULT:
do_no_context(regs);
break;
case VM_FAULT_SIGNAL:
@@ -269,6 +271,9 @@ static noinline void do_fault_error(struct pt_regs *regs,
int fault)
*/
static inline int do_exception(struct pt_regs *regs, int access)
{
+#ifdef CONFIG_PGSTE
+ struct gmap *gmap;
+#endif
struct task_struct *tsk;
struct mm_struct *mm;
struct vm_area_struct *vma;
@@ -309,9 +314,10 @@ static inline int do_exception(struct pt_regs *regs, int
access)
down_read(&mm->mmap_sem);
#ifdef CONFIG_PGSTE
- if ((current->flags & PF_VCPU) && S390_lowcore.gmap) {
- address = __gmap_fault(address,
- (struct gmap *) S390_lowcore.gmap);
+ gmap = (struct gmap *)
+ ((current->flags & PF_VCPU) ? S390_lowcore.gmap : 0);
+ if (gmap) {
+ address = __gmap_fault(address, gmap);
if (address == -EFAULT) {
fault = VM_FAULT_BADMAP;
goto out_up;
@@ -320,6 +326,8 @@ static inline int do_exception(struct pt_regs *regs, int
access)
fault = VM_FAULT_OOM;
goto out_up;
}
+ if (gmap->pfault_enabled)
+ flags |= FAULT_FLAG_RETRY_NOWAIT;
}
#endif
@@ -376,9 +384,19 @@ retry:
regs, address);
}
if (fault & VM_FAULT_RETRY) {
+#ifdef CONFIG_PGSTE
+ if (gmap && (flags & FAULT_FLAG_RETRY_NOWAIT)) {
+ /* FAULT_FLAG_RETRY_NOWAIT has been set,
+ * mmap_sem has not been released */
+ current->thread.gmap_pfault = 1;
+ fault = VM_FAULT_PFAULT;
+ goto out_up;
+ }
+#endif
/* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
* of starvation. */
- flags &= ~FAULT_FLAG_ALLOW_RETRY;
+ flags &= ~(FAULT_FLAG_ALLOW_RETRY |
+ FAULT_FLAG_RETRY_NOWAIT);
flags |= FAULT_FLAG_TRIED;
down_read(&mm->mmap_sem);
goto retry;
--
1.8.3.1
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