Am 06.02.2012 10:57, schrieb Gleb Natapov: > 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 <kw...@redhat.com> >>>> --- >>>> 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.
Good point. The easy, but IMHO somewhat hackish way to fix it is to only call svm_update_cpl() if the VM flag has changed. For the real thing, we'd have to know whether we are in the middle of a mode switch, i.e. whether the segment selector is a protected mode or real mode selector. I don't think we have this information, do we? Kevin -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html