On Tue, Feb 26, 2019 at 10:17 AM Singh, Brijesh <brijesh.singh@xxxxxxx> wrote: > > > > On 2/26/19 11:12 AM, Jim Mattson wrote: > > On Tue, Feb 26, 2019 at 9:02 AM Singh, Brijesh <brijesh.singh@xxxxxxx> wrote: > >> > >> Errata#1096: > >> > >> On a nested data page fault when CR.SMAP=1 and the guest data read > >> generates a SMAP violation, GuestInstrBytes field of the VMCB on a > >> VMEXIT will incorrectly return 0h instead the correct guest > >> instruction bytes . > >> > >> Recommend Workaround: > >> > >> To determine what instruction the guest was executing the hypervisor > >> will have to decode the instruction at the instruction pointer. > >> > >> The recommended workaround can not be implemented for the SEV > >> guest because guest memory is encrypted with the guest specific key, > >> and instruction decoder will not be able to decode the instruction > >> bytes. If we hit this errata in the SEV guest then log the message > >> and request a guest shutdown. > >> > >> Reported-by: Venkatesh Srinivas <venkateshs@xxxxxxxxxx> > >> Cc: Jim Mattson <jmattson@xxxxxxxxxx> > >> Cc: Tom Lendacky <thomas.lendacky@xxxxxxx> > >> Cc: Borislav Petkov <bp@xxxxxxxxx> > >> Cc: Joerg Roedel <joro@xxxxxxxxxx> > >> Cc: "Radim Krčmář" <rkrcmar@xxxxxxxxxx> > >> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx> > >> Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx> > >> --- > >> > >> Change since v2: > >> * rename the callback emulate_instruction_possible->need_emulation_on_page_fault > > > > This function still seems poorly named. You already know that you > > *need* emulation by the time you call it, don't you? > > > > > We know that we are going to require emulation to handle this #PF. > > How about can_emulate_on_page_fault(..) ? Any other suggestions ? Isn't "can_emulate_on_page_fault()" exactly the same as "!sev_guest()"? The function in question also returns false when CPL != 3 or CR4.SMAP is clear. I think it's difficult to name this function because the function is essentially answering two unrelated questions: 1) Did we encounter erratum 1096? 2) Can we emulate an instruction to make forward progress? I would suggest that this be broken up into two separate functions: one which determines whether or not we've encountered erratum 1096 and another which determines whether or not SEV is enabled. I suspect that a function to answer the SEV question on its own is going to prove itself quite useful over time.
