[PATCH] KVM: emulate: warn on invalid or uninitialized exception numbers

From: Paolo Bonzini
Date: Wed Aug 20 2014 - 07:24:53 EST


These were reported when running Jailhouse on AMD processors.

Initialize ctxt->exception.vector with an invalid exception number,
and warn if it remained invalid even though the emulator got
an X86EMUL_PROPAGATE_FAULT return code.

Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
arch/x86/kvm/emulate.c | 5 ++++-
arch/x86/kvm/x86.c | 1 +
2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 4fbf4b598f92..e5bf13003cd2 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -527,6 +527,7 @@ static unsigned long seg_base(struct x86_emulate_ctxt *ctxt, int seg)
static int emulate_exception(struct x86_emulate_ctxt *ctxt, int vec,
u32 error, bool valid)
{
+ WARN_ON(vec > 0x1f);
ctxt->exception.vector = vec;
ctxt->exception.error_code = error;
ctxt->exception.error_code_valid = valid;
@@ -4827,8 +4828,10 @@ writeback:
ctxt->eip = ctxt->_eip;

done:
- if (rc == X86EMUL_PROPAGATE_FAULT)
+ if (rc == X86EMUL_PROPAGATE_FAULT) {
+ WARN_ON(ctxt->exception.vector > 0x1f);
ctxt->have_exception = true;
+ }
if (rc == X86EMUL_INTERCEPTED)
return EMULATION_INTERCEPTED;

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 737b4bdac41c..cd718c01cdf1 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5248,6 +5248,7 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu,

ctxt->interruptibility = 0;
ctxt->have_exception = false;
+ ctxt->exception.vector = -1;
ctxt->perm_ok = false;

ctxt->ud = emulation_type & EMULTYPE_TRAP_UD;
--
1.8.3.1

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