From 33e3885de25148e00595c4dd808d6eb15db2edcf Mon Sep 17 00:00:00 2001 From: Avi Kivity Date: Wed, 21 May 2008 15:34:25 +0300 Subject: KVM: x86 emulator: fix hypercall return value on AMD The hypercall instructions on Intel and AMD are different. KVM allows the guest to choose one or the other (the default is Intel), and if the guest chooses incorrectly, KVM will patch it at runtime to select the correct instruction. This allows live migration between Intel and AMD machines. This patching occurs in the x86 emulator. The current code also executes the hypercall. Unfortunately, the tail end of the x86 emulator code also executes, overwriting the return value of the hypercall with the original contents of rax (which happens to be the hypercall number). Fix not by executing the hypercall in the emulator context; instead let the guest reissue the patched instruction and execute the hypercall via the normal path. Signed-off-by: Avi Kivity --- arch/x86/kvm/x86_emulate.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'arch/x86/kvm/x86_emulate.c') diff --git a/arch/x86/kvm/x86_emulate.c b/arch/x86/kvm/x86_emulate.c index 8a96320ab071..932f216d890c 100644 --- a/arch/x86/kvm/x86_emulate.c +++ b/arch/x86/kvm/x86_emulate.c @@ -1727,7 +1727,8 @@ twobyte_insn: if (rc) goto done; - kvm_emulate_hypercall(ctxt->vcpu); + /* Let the processor re-execute the fixed hypercall */ + c->eip = ctxt->vcpu->arch.rip; /* Disable writeback. */ c->dst.type = OP_NONE; break; -- cgit v1.2.3