On 02/09/2011 02:56 PM, Roedel, Joerg wrote:
On Wed, Feb 09, 2011 at 05:43:28AM -0500, Andre Przywara wrote:
> Roedel, Joerg wrote:
> > On Tue, Feb 08, 2011 at 07:22:29PM -0500, Andre Przywara wrote:
> >> Somehow the code line advancing the RIP and checking for exceptions
> >> got dropped between the post on the ML and the commit.
> >> Add it again to let guests boot on upcoming AMD CPUs again.
> >>
> >> Reported-by: Joerg Roedel<joerg.roe...@amd.com>
> >> Signed-off-by: Andre Przywara<andre.przyw...@amd.com>
> >> ---
> >> arch/x86/kvm/svm.c | 1 +
> >> 1 files changed, 1 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> >> index 25bd1bc..be06e58 100644
> >> --- a/arch/x86/kvm/svm.c
> >> +++ b/arch/x86/kvm/svm.c
> >> @@ -2776,6 +2776,7 @@ static int dr_interception(struct vcpu_svm *svm)
> >> if (!err)
> >> kvm_register_write(&svm->vcpu, reg, val);
> >> }
> >> + kvm_complete_insn_gp(&svm->vcpu, err);
> >
> > Any exception check takes presedence over the intercept. So a call to
> > skip_emulated_instruction should be sufficient here.
> You are right, but I think this way the implementation is cleaner and
> more generic. If there is no exception condition detected (err==0), then
> the call will just do skip_emulated_instruction anyway.
> But as I write this, I see that err is not initialized, so I'd propose
> this corrected version of the patch instead.
One function call is not less clean than another and this function call
has more overhead.
Beside that, looking at kvm_set_dr this function only returns 1 if one
tries to set dr4 or dr5 while CR4.DE is not set. In this case the
function you call here would inject a #GP but architecturally a #UD
is required.
This problem doesn't matter too much because the exceptions take
precedence over the intercept anyway so it is sufficient to call
skip_emulated_instruction here.
Given that the exception is incorrect I agree
skip_emulated_instruction() is a better choice here.
--
error compiling committee.c: too many arguments to function
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