Il 04/09/2014 09:02, Gleb Natapov ha scritto:
> On Tue, Sep 02, 2014 at 05:13:49PM +0200, Paolo Bonzini wrote:
>> > This is required for the following patch to work correctly. If a nested
>> > page
>> > fault happens during emulation, we must inject a vmexit, not a page fault.
>> > Luckily we already have the required machinery: it is enough to return
>> > X86EMUL_INTERCEPTED instead of X86EMUL_PROPAGATE_FAULT.
>> >
> I wonder why this patch is needed. X86EMUL_PROPAGATE_FAULT causes
> ctxt->have_exception to be set to true in x86_emulate_insn().
> x86_emulate_instruction() checks ctxt->have_exception and calls
> inject_emulated_exception() if it is true. inject_emulated_exception()
> calls kvm_propagate_fault() where we check if the fault was nested and
> generate vmexit or a page fault accordingly.
Good question. :)
If you do that, KVM gets down to the "if (writeback)" and writes the
ctxt->eip from L2 into the L1 EIP.
Possibly this patch can be replaced by just this?
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 022513b..475e979 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5312,7 +5312,7 @@ restart:
if (ctxt->have_exception) {
inject_emulated_exception(vcpu);
- r = EMULATE_DONE;
+ return EMULATE_DONE;
} else if (vcpu->arch.pio.count) {
if (!vcpu->arch.pio.in) {
/* FIXME: return into emulator if single-stepping. */
But I'm not sure how to test it, and I like the idea of treating nested page
faults like other nested vmexits during emulation (which is what this patch
does).
If I included this patch, I could then remove kvm_propagate_fault
like (I think) this:
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 92493e10937c..e096db566ac2 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4910,9 +4902,10 @@ static void toggle_interruptibility(struct kvm_vcpu
*vcpu, u32 mask)
static void inject_emulated_exception(struct kvm_vcpu *vcpu)
{
struct x86_emulate_ctxt *ctxt = &vcpu->arch.emulate_ctxt;
- if (ctxt->exception.vector == PF_VECTOR)
- kvm_propagate_fault(vcpu, &ctxt->exception);
- else if (ctxt->exception.error_code_valid)
+ if (ctxt->exception.vector == PF_VECTOR) {
+ WARN_ON(fault->nested_page_fault);
+ vcpu->arch.walk_mmu->inject_page_fault(vcpu, fault);
+ } else if (ctxt->exception.error_code_valid)
kvm_queue_exception_e(vcpu, ctxt->exception.vector,
ctxt->exception.error_code);
else
What do you think?
Paolo
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
