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| author | Nadav Amit <namit@cs.technion.ac.il> | 2014-12-25 02:52:16 +0200 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2015-01-09 10:24:11 +0100 |
| commit | c205fb7d7d4f81e46fc577b707ceb9e356af1456 (patch) | |
| tree | b73dbbae61efb80a231368f88f319688bc71d8b1 /arch/x86/kvm/emulate.c | |
| parent | 7e71a59b250330fd52ee7293eb9d31952f16682e (diff) | |
| download | lwn-c205fb7d7d4f81e46fc577b707ceb9e356af1456.tar.gz lwn-c205fb7d7d4f81e46fc577b707ceb9e356af1456.zip | |
KVM: x86: #PF error-code on R/W operations is wrong
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 <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/emulate.c')
| -rw-r--r-- | arch/x86/kvm/emulate.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index d949287ed010..ef23c1e5fa9f 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -4909,8 +4909,12 @@ 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; |