Messages in this thread | | | Date | Mon, 26 Aug 2019 07:06:51 -0700 | From | Sean Christopherson <> | Subject | Re: [PATCH] KVM: x86: Don't update RIP or do single-step on faulting emulation |
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On Fri, Aug 23, 2019 at 03:46:20PM -0700, Andy Lutomirski wrote: > On Fri, Aug 23, 2019 at 1:55 PM Sean Christopherson > <sean.j.christopherson@intel.com> wrote: > > > > Don't advance RIP or inject a single-step #DB if emulation signals a > > fault. This logic applies to all state updates that are conditional on > > clean retirement of the emulation instruction, e.g. updating RFLAGS was > > previously handled by commit 38827dbd3fb85 ("KVM: x86: Do not update > > EFLAGS on faulting emulation"). > > > > Not advancing RIP is likely a nop, i.e. ctxt->eip isn't updated with > > ctxt->_eip until emulation "retires" anyways. Skipping #DB injection > > fixes a bug reported by Andy Lutomirski where a #UD on SYSCALL due to > > invalid state with RFLAGS.RF=1 would loop indefinitely due to emulation > > EFLAGS.TF=1
It's always some mundane detail...
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