Re: buggy emulate_int_real

["Serge E. Hallyn" <serge@hallyn.com>]

Quoting Serge E. Hallyn (serge@hallyn.com):
> Quoting Jan Kiszka (jan.kiszka@web.de):
> > From a brief refresh-reading, I would say
> > 
> > if (interrupt.soft || kvm_exception_is_soft(nr))
> >     increment_eip_by_inst_len
> > 
> > but only for those interrupts/exceptions which were raised by the
> > triggering instructions, _not_ for exceptions raise while processing
> > them (e.g. a page fault while accessing the IDT).
> > 
> > Jan
> 
> Ok, thanks guys.  I'm currently trying a compile of the following.

With the obvious fixes, that turns into the below, which seems to be
working for me:

>From 555696f355ec2db9f4919f5e363355a2671b15a5 Mon Sep 17 00:00:00 2001
From: Serge E. Hallyn <serge.hallyn@canonical.com>
Date: Tue, 12 Apr 2011 22:18:40 +0100
Subject: [PATCH 1/1] kvm: fix push of wrong eip when doing softint

When doing a soft int, we need to bump eip before pushing it to
the stack.  Otherwise we'll do the int a second time.

Signed-off-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
---
 arch/x86/kvm/vmx.c |   12 +++++++++---
 arch/x86/kvm/x86.c |    3 ++-
 arch/x86/kvm/x86.h |    2 +-
 3 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index bf89ec2..3aad96c 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1053,7 +1053,10 @@ static void vmx_queue_exception(struct kvm_vcpu *vcpu, unsigned nr,
 	}
 
 	if (vmx->rmode.vm86_active) {
-		if (kvm_inject_realmode_interrupt(vcpu, nr) != EMULATE_DONE)
+		int inc_eip = 0;
+		if (kvm_exception_is_soft(nr))
+			inc_eip = vcpu->arch.event_exit_inst_len;
+		if (kvm_inject_realmode_interrupt(vcpu, nr, inc_eip) != EMULATE_DONE)
 			kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu);
 		return;
 	}
@@ -2871,7 +2874,10 @@ static void vmx_inject_irq(struct kvm_vcpu *vcpu)
 
 	++vcpu->stat.irq_injections;
 	if (vmx->rmode.vm86_active) {
-		if (kvm_inject_realmode_interrupt(vcpu, irq) != EMULATE_DONE)
+		int inc_eip = 0;
+		if (vcpu->arch.interrupt.soft)
+			inc_eip = vcpu->arch.event_exit_inst_len;
+		if (kvm_inject_realmode_interrupt(vcpu, irq, inc_eip) != EMULATE_DONE)
 			kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu);
 		return;
 	}
@@ -2905,7 +2911,7 @@ static void vmx_inject_nmi(struct kvm_vcpu *vcpu)
 
 	++vcpu->stat.nmi_injections;
 	if (vmx->rmode.vm86_active) {
-		if (kvm_inject_realmode_interrupt(vcpu, NMI_VECTOR) != EMULATE_DONE)
+		if (kvm_inject_realmode_interrupt(vcpu, NMI_VECTOR, 0) != EMULATE_DONE)
 			kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu);
 		return;
 	}
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index bcc0efc..8911622 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4293,7 +4293,7 @@ static void init_emulate_ctxt(struct kvm_vcpu *vcpu)
 	memcpy(c->regs, vcpu->arch.regs, sizeof c->regs);
 }
 
-int kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq)
+int kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq, int inc_eip)
 {
 	struct decode_cache *c = &vcpu->arch.emulate_ctxt.decode;
 	int ret;
@@ -4303,6 +4303,7 @@ int kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq)
 	vcpu->arch.emulate_ctxt.decode.op_bytes = 2;
 	vcpu->arch.emulate_ctxt.decode.ad_bytes = 2;
 	vcpu->arch.emulate_ctxt.decode.eip = vcpu->arch.emulate_ctxt.eip;
+	vcpu->arch.emulate_ctxt.decode.eip += inc_eip;
 	ret = emulate_int_real(&vcpu->arch.emulate_ctxt, &emulate_ops, irq);
 
 	if (ret != X86EMUL_CONTINUE)
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index c600da8..e407ed3 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -77,7 +77,7 @@ static inline u32 bit(int bitno)
 
 void kvm_before_handle_nmi(struct kvm_vcpu *vcpu);
 void kvm_after_handle_nmi(struct kvm_vcpu *vcpu);
-int kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq);
+int kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq, int inc_eip);
 
 void kvm_write_tsc(struct kvm_vcpu *vcpu, u64 data);
 
-- 
1.7.0.4