From: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Add FAULT_FLAG_RETRY_NOWAIT to the fault flags if the host is processing
a guest fault. In case of a fault retry exit sie64a() with the gmap_fault
indication set. This makes it possible to handle asynchronous page faults
without the need for mm notifiers.
Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
---
arch/s390/include/asm/pgtable.h | 1 +
arch/s390/include/asm/processor.h | 1 +
arch/s390/mm/fault.c | 28 +++++++++++++++++++++++-----
arch/s390/mm/pgtable.c | 7 +++++++
4 files changed, 32 insertions(+), 5 deletions(-)
diff -urpN linux-2.6/arch/s390/include/asm/pgtable.h linux-2.6-patched/arch/s390/include/asm/pgtable.h
--- linux-2.6/arch/s390/include/asm/pgtable.h 2011-11-17 10:03:47.000000000 +0100
+++ linux-2.6-patched/arch/s390/include/asm/pgtable.h 2011-11-17 10:03:53.000000000 +0100
@@ -688,6 +688,7 @@ int gmap_unmap_segment(struct gmap *gmap
unsigned long __gmap_fault(unsigned long address, struct gmap *);
unsigned long gmap_fault(unsigned long address, struct gmap *);
void gmap_discard(unsigned long from, unsigned long to, struct gmap *);
+int gmap_pfault(struct gmap *gmap);
/*
* Certain architectures need to do special things when PTEs
diff -urpN linux-2.6/arch/s390/include/asm/processor.h linux-2.6-patched/arch/s390/include/asm/processor.h
--- linux-2.6/arch/s390/include/asm/processor.h 2011-11-17 10:03:39.000000000 +0100
+++ linux-2.6-patched/arch/s390/include/asm/processor.h 2011-11-17 10:03:53.000000000 +0100
@@ -83,6 +83,7 @@ struct thread_struct {
unsigned long prot_addr; /* address of protection-excep. */
unsigned int trap_no;
unsigned long gmap_addr; /* address of last gmap fault. */
+ unsigned int gmap_pfault; /* bool to indicate a guest pfault */
struct per_regs per_user; /* User specified PER registers */
struct per_event per_event; /* Cause of the last PER trap */
/* pfault_wait is used to block the process on a pfault event */
diff -urpN linux-2.6/arch/s390/mm/fault.c linux-2.6-patched/arch/s390/mm/fault.c
--- linux-2.6/arch/s390/mm/fault.c 2011-11-17 10:03:49.000000000 +0100
+++ linux-2.6-patched/arch/s390/mm/fault.c 2011-11-17 10:03:53.000000000 +0100
@@ -52,6 +52,7 @@
#define VM_FAULT_BADCONTEXT 0x010000
#define VM_FAULT_BADMAP 0x020000
#define VM_FAULT_BADACCESS 0x040000
+#define VM_FAULT_PFAULT 0x080000
static unsigned long store_indication;
@@ -242,6 +243,7 @@ static noinline void do_fault_error(stru
return;
}
case VM_FAULT_BADCONTEXT:
+ case VM_FAULT_PFAULT:
do_no_context(regs, int_code, trans_exc_code);
break;
default: /* fault & VM_FAULT_ERROR */
@@ -276,6 +278,9 @@ static noinline void do_fault_error(stru
static inline int do_exception(struct pt_regs *regs, int access,
unsigned long trans_exc_code)
{
+#ifdef CONFIG_PGSTE
+ struct gmap *gmap;
+#endif
struct task_struct *tsk;
struct mm_struct *mm;
struct vm_area_struct *vma;
@@ -306,9 +311,10 @@ static inline int do_exception(struct pt
down_read(&mm->mmap_sem);
#ifdef CONFIG_PGSTE
- if (test_tsk_thread_flag(current, TIF_SIE) && S390_lowcore.gmap) {
- address = __gmap_fault(address,
- (struct gmap *) S390_lowcore.gmap);
+ gmap = (struct gmap *)
+ (test_thread_flag(TIF_SIE) ? S390_lowcore.gmap : 0);
+ if (gmap) {
+ address = __gmap_fault(address, gmap);
if (address == -EFAULT) {
fault = VM_FAULT_BADMAP;
goto out_up;
@@ -317,6 +323,7 @@ static inline int do_exception(struct pt
fault = VM_FAULT_OOM;
goto out_up;
}
+ flags |= FAULT_FLAG_RETRY_NOWAIT;
}
#endif
@@ -368,10 +375,21 @@ retry:
regs, address);
}
if (fault & VM_FAULT_RETRY) {
+#ifdef CONFIG_PGSTE
+ if (gmap) {
+ /* FAULT_FLAG_RETRY_NOWAIT has been set,
+ * mmap_sem has not been released. */
+ if (gmap_pfault(gmap)) {
+ fault = VM_FAULT_PFAULT;
+ goto out_up;
+ }
+ } else
+#endif
+ down_read(&mm->mmap_sem);
/* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
* of starvation. */
- flags &= ~FAULT_FLAG_ALLOW_RETRY;
- down_read(&mm->mmap_sem);
+ flags &= ~(FAULT_FLAG_ALLOW_RETRY |
+ FAULT_FLAG_RETRY_NOWAIT);
goto retry;
}
}
diff -urpN linux-2.6/arch/s390/mm/pgtable.c linux-2.6-patched/arch/s390/mm/pgtable.c
--- linux-2.6/arch/s390/mm/pgtable.c 2011-11-17 10:03:47.000000000 +0100
+++ linux-2.6-patched/arch/s390/mm/pgtable.c 2011-11-17 10:03:53.000000000 +0100
@@ -398,6 +398,7 @@ unsigned long __gmap_fault(unsigned long
pmd_t *pmd;
current->thread.gmap_addr = address;
+ current->thread.gmap_pfault = 0;
mm = gmap->mm;
/* Walk the gmap address space page table */
table = gmap->table + ((address >> 53) & 0x7ff);
@@ -514,6 +515,12 @@ void gmap_discard(unsigned long from, un
}
EXPORT_SYMBOL_GPL(gmap_discard);
+int gmap_pfault(struct gmap *gmap)
+{
+ current->thread.gmap_pfault = 1;
+ return 1;
+}
+
void gmap_unmap_notifier(struct mm_struct *mm, unsigned long *table)
{
struct gmap_rmap *rmap, *next;
--
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