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 <dingel@xxxxxxxxxxxxxxxxxx>
---
arch/s390/include/asm/pgtable.h | 2 ++
arch/s390/include/asm/processor.h | 1 +
arch/s390/kvm/kvm-s390.c | 13 +++++++++++++
arch/s390/mm/fault.c | 26 ++++++++++++++++++++++----
4 files changed, 38 insertions(+), 4 deletions(-)
diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 0ea4e59..4a4cc64 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -740,6 +740,7 @@ 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;
@@ -748,6 +749,7 @@ struct gmap {
unsigned long asce;
void *private;
struct list_head crst_list;
+ unsigned long pfault_enabled;
};
/**
diff --git a/arch/s390/include/asm/processor.h b/arch/s390/include/asm/processor.h
index 6b49987..4fa96ca 100644
--- a/arch/s390/include/asm/processor.h
+++ b/arch/s390/include/asm/processor.h
@@ -77,6 +77,7 @@ 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 ba694d2..702daca 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -682,6 +682,15 @@ static int kvm_s390_handle_requests(struct kvm_vcpu *vcpu)
return 0;
}
+static void kvm_arch_fault_in_sync(struct kvm_vcpu *vcpu)
+{
+ hva_t fault = gmap_fault(current->thread.gmap_addr, vcpu->arch.gmap);
+ struct mm_struct *mm = current->mm;
+ down_read(&mm->mmap_sem);
+ get_user_pages(current, mm, fault, 1, 1, 0, NULL, NULL);
+ up_read(&mm->mmap_sem);
+}
+
static int __vcpu_run(struct kvm_vcpu *vcpu)
{
int rc;
@@ -715,6 +724,10 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
if (rc < 0) {
if (kvm_is_ucontrol(vcpu->kvm)) {
rc = SIE_INTERCEPT_UCONTROL;
+ } else if (current->thread.gmap_pfault) {
+ kvm_arch_fault_in_sync(vcpu);
+ current->thread.gmap_pfault = 0;
+ rc = 0;
} else {
VCPU_EVENT(vcpu, 3, "%s", "fault in sie instruction");
trace_kvm_s390_sie_fault(vcpu);
diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index 047c3e4..7d4c4b1 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;
@@ -307,9 +312,10 @@ 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;
@@ -318,6 +324,8 @@ static inline int do_exception(struct pt_regs *regs, int access)
fault = VM_FAULT_OOM;
goto out_up;
}
+ if (test_bit(1, &gmap->pfault_enabled))
+ flags |= FAULT_FLAG_RETRY_NOWAIT;
}
#endif
@@ -374,9 +382,19 @@ 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;
--
1.8.2.2
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