On Sat, Jul 31, 2010 at 08:25:13PM +0300, Avi Kivity wrote:
>  On 07/29/2010 03:11 PM, Gleb Natapov wrote:
> >No need to update vcpu state since instruction is in the middle of the
> >emulation.
> >
> >Signed-off-by: Gleb Natapov<[email protected]>
> >---
> >  arch/x86/kvm/x86.c |   31 +++++++++++++------------------
> >  1 files changed, 13 insertions(+), 18 deletions(-)
> >
> >diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> >index 76fbc32..7e5f075 100644
> >--- a/arch/x86/kvm/x86.c
> >+++ b/arch/x86/kvm/x86.c
> >@@ -4057,32 +4057,27 @@ restart:
> >             return handle_emulation_failure(vcpu);
> >     }
> >
> >-    toggle_interruptibility(vcpu, vcpu->arch.emulate_ctxt.interruptibility);
> >-    kvm_x86_ops->set_rflags(vcpu, vcpu->arch.emulate_ctxt.eflags);
> >-    memcpy(vcpu->arch.regs, c->regs, sizeof c->regs);
> >-    kvm_rip_write(vcpu, vcpu->arch.emulate_ctxt.eip);
> >+    r = EMULATE_DONE;
> >
> >-    if (vcpu->arch.emulate_ctxt.exception>= 0) {
> >+    if (vcpu->arch.emulate_ctxt.exception>= 0)
> >             inject_emulated_exception(vcpu);
> >-            return EMULATE_DONE;
> >-    }
> >-
> >-    if (vcpu->arch.pio.count) {
> >+    else if (vcpu->arch.pio.count) {
> >             if (!vcpu->arch.pio.in)
> >                     vcpu->arch.pio.count = 0;
> >-            return EMULATE_DO_MMIO;
> >-    }
> >-
> >-    if (vcpu->mmio_needed) {
> >+            r = EMULATE_DO_MMIO;
> >+    } else if (vcpu->mmio_needed) {
> >             if (vcpu->mmio_is_write)
> >                     vcpu->mmio_needed = 0;
> >-            return EMULATE_DO_MMIO;
> >-    }
> >-
> >-    if (vcpu->arch.emulate_ctxt.restart)
> >+            r = EMULATE_DO_MMIO;
> >+    } else if (vcpu->arch.emulate_ctxt.restart)
> >             goto restart;
> >
> >-    return EMULATE_DONE;
> >+    toggle_interruptibility(vcpu, vcpu->arch.emulate_ctxt.interruptibility);
> >+    kvm_x86_ops->set_rflags(vcpu, vcpu->arch.emulate_ctxt.eflags);
> >+    memcpy(vcpu->arch.regs, c->regs, sizeof c->regs);
> >+    kvm_rip_write(vcpu, vcpu->arch.emulate_ctxt.eip);
> >+
> >+    return r;
> >  }
> >  EXPORT_SYMBOL_GPL(emulate_instruction);
> >
> 
> What about kvm-tpr-opt.c?  It uses rip after pio.
> 
It uses rip _during_ pio. And pio emulation changes rip
only at the end of emulation.

> It's true that it usually doesn't go through the emulator.
> 
> -- 
> I have a truly marvellous patch that fixes the bug which this
> signature is too narrow to contain.

--
                        Gleb.
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