When emulating an instruction that reads the destination memory operand (i.e.,
instructions without the Mov flag in the emulator), the operand is first read.
If a page-fault is detected in this phase, the error-code which would be
delivered to the VM does not indicate that the access that caused the exception
is a write one. This does not conform with real hardware, and may cause the VM
to enter the page-fault handler twice for no reason (once for read, once for
write).
Signed-off-by: Nadav Amit <na...@cs.technion.ac.il>
---
arch/x86/include/asm/kvm_host.h | 12 ++++++++++++
arch/x86/kvm/emulate.c | 6 +++++-
arch/x86/kvm/mmu.h | 12 ------------
3 files changed, 17 insertions(+), 13 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 73ccb12..d6f90ca 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -162,6 +162,18 @@ enum {
#define DR7_FIXED_1 0x00000400
#define DR7_VOLATILE 0xffff2bff
+#define PFERR_PRESENT_BIT 0
+#define PFERR_WRITE_BIT 1
+#define PFERR_USER_BIT 2
+#define PFERR_RSVD_BIT 3
+#define PFERR_FETCH_BIT 4
+
+#define PFERR_PRESENT_MASK (1U << PFERR_PRESENT_BIT)
+#define PFERR_WRITE_MASK (1U << PFERR_WRITE_BIT)
+#define PFERR_USER_MASK (1U << PFERR_USER_BIT)
+#define PFERR_RSVD_MASK (1U << PFERR_RSVD_BIT)
+#define PFERR_FETCH_MASK (1U << PFERR_FETCH_BIT)
+
/* apic attention bits */
#define KVM_APIC_CHECK_VAPIC 0
/*
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 7a9697f..e5a84be 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -4941,8 +4941,12 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
/* optimisation - avoid slow emulated read if Mov */
rc = segmented_read(ctxt, ctxt->dst.addr.mem,
&ctxt->dst.val, ctxt->dst.bytes);
- if (rc != X86EMUL_CONTINUE)
+ if (rc != X86EMUL_CONTINUE) {
+ if (rc == X86EMUL_PROPAGATE_FAULT &&
+ ctxt->exception.vector == PF_VECTOR)
+ ctxt->exception.error_code |= PFERR_WRITE_MASK;
goto done;
+ }
}
ctxt->dst.orig_val = ctxt->dst.val;
diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index 6b34876b..daae711 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -44,18 +44,6 @@
#define PT_DIRECTORY_LEVEL 2
#define PT_PAGE_TABLE_LEVEL 1
-#define PFERR_PRESENT_BIT 0
-#define PFERR_WRITE_BIT 1
-#define PFERR_USER_BIT 2
-#define PFERR_RSVD_BIT 3
-#define PFERR_FETCH_BIT 4
-
-#define PFERR_PRESENT_MASK (1U << PFERR_PRESENT_BIT)
-#define PFERR_WRITE_MASK (1U << PFERR_WRITE_BIT)
-#define PFERR_USER_MASK (1U << PFERR_USER_BIT)
-#define PFERR_RSVD_MASK (1U << PFERR_RSVD_BIT)
-#define PFERR_FETCH_MASK (1U << PFERR_FETCH_BIT)
-
static inline u64 rsvd_bits(int s, int e)
{
return ((1ULL << (e - s + 1)) - 1) << s;
--
1.9.1
--
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