On Mon, Feb 06, 2012 at 10:18:35AM +0100, Kevin Wolf wrote:
> Am 05.02.2012 12:16, schrieb Gleb Natapov:
> > On Fri, Feb 03, 2012 at 07:29:24PM +0100, Kevin Wolf wrote:
> >> Keep CPL at 0 in real mode and at 3 in VM86. In protected/long mode, use
> >> RPL rather than DPL of the code segment.
> >>
> >> Signed-off-by: Kevin Wolf <kwolf@xxxxxxxxxx>
> >> ---
> >> arch/x86/kvm/svm.c | 19 ++++++++++++++++---
> >> 1 files changed, 16 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> >> index 6a977c1..4124a7e 100644
> >> --- a/arch/x86/kvm/svm.c
> >> +++ b/arch/x86/kvm/svm.c
> >> @@ -1263,6 +1263,21 @@ static void svm_vcpu_put(struct kvm_vcpu *vcpu)
> >> wrmsrl(host_save_user_msrs[i], svm->host_user_msrs[i]);
> >> }
> >>
> >> +static void svm_update_cpl(struct kvm_vcpu *vcpu)
> >> +{
> >> + struct vcpu_svm *svm = to_svm(vcpu);
> >> + int cpl;
> >> +
> >> + if (!is_protmode(vcpu))
> >> + cpl = 0;
> >> + else if (svm->vmcb->save.rflags & X86_EFLAGS_VM)
> >> + cpl = 3;
> >> + else
> >> + cpl = svm->vmcb->save.cs.selector & 0x3;
> >> +
> >> + svm->vmcb->save.cpl = cpl;
> >> +}
> >> +
> > As you probably know already I think cpl should be updated in
> > svm_get_rflags() too. With current patch restoring CS segment
> > register before rflags register after migration may cause cpl
> > to get wrong value for instance.
>
> I think you mean set_rflags rather than get_rflags?
>
Uh, yes.
> Patch 4 adds this with the set_rflags emulator callback.
>
Sorry, missed that, I expected it to be in this patch for some reason.
I think calling svm_update_cpl() from set_rflags() is incorrect though.
svm_update_cpl() checks cr0 so if guest does "mov 1, %cr0; popf" and
popf happens to be emulated it will change cpl to cs&3 which is
incorrect.
--
Gleb.
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