Re: [PATCH kvm-unit-tests 2/2] vmx: fix expected results of new EPT tests

[Paolo Bonzini <pbonzini@redhat.com>]

----- Original Message -----
> From: "Peter Feiner" <pfeiner@google.com>
> To: "Paolo Bonzini" <pbonzini@redhat.com>
> Cc: kvm@vger.kernel.org, "David Matlack" <dmatlack@google.com>
> Sent: Thursday, May 11, 2017 5:58:49 PM
> Subject: Re: [PATCH kvm-unit-tests 2/2] vmx: fix expected results of new EPT tests
> 
> On Thu, May 11, 2017 at 4:23 AM, Paolo Bonzini <pbonzini@redhat.com> wrote:
> > Remove RD/EX exchange hack which we can fix in KVM; mark page table
> > accesses as read/write when EPT A/D is enabled, and expect them to
> > be handled as read/write even with disabled EPT A/D bits (even though
> > the exit qualification says otherwise).
> 
> I assume this is a stopgap change. I mean, you're asserting for the
> wrong behavior just so the tests pass. Correct?

No, I've tried the tests on upstream Linux with eptad=0 (so that EPT A/D
is not used by KVM on the host) and they also hang with an infinite stream
of EPT violations.  See the KVM patch I sent which also explains the hang
in the comments ("[PATCH 2/2] KVM: nVMX: fix nEPT handling of guest page
table accesses").

So it seems to me that this is the expected behavior of the processor
even when A/D bits are disabled.  I haven't tested on a processor with
EPT but without A/D bits though.

Paolo