From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Jim Mattson <jmattson@google.com>
Cc: Nadav Amit <nadav.amit@gmail.com>,
Paolo Bonzini <pbonzini@redhat.com>,
kvm list <kvm@vger.kernel.org>
Subject: Re: [kvm-unit-tests PATCH] x86: Fix max VMCS field encoding index check
Date: Tue, 17 Dec 2019 16:24:10 -0800 [thread overview]
Message-ID: <20191218002410.GN11771@linux.intel.com> (raw)
In-Reply-To: <CALMp9eT+K7qwLeBb231OjNwqTaS4XE6Ci+-j_b+a=0JU__HEqg@mail.gmail.com>
On Fri, Dec 13, 2019 at 09:30:45AM -0800, Jim Mattson wrote:
> On Fri, Dec 13, 2019 at 1:13 AM Nadav Amit <nadav.amit@gmail.com> wrote:
> >
> > > On Dec 13, 2019, at 12:59 AM, Jim Mattson <jmattson@google.com> wrote:
> > >
> > > On Sat, May 18, 2019 at 4:58 PM Nadav Amit <nadav.amit@gmail.com> wrote:
> > >> The test that checks the maximum VMCS field encoding does not probe all
> > >> possible VMCS fields. As a result it might fail since the actual
> > >> IA32_VMX_VMCS_ENUM.MAX_INDEX would be higher than the expected value.
> > >>
> > >> Change the test to check that the maximum of the supported probed
> > >> VMCS fields is lower/equal than the actual reported
> > >> IA32_VMX_VMCS_ENUM.MAX_INDEX.
> > >
> > > Wouldn't it be better to probe all possible VMCS fields and keep the
> > > test for equality?
> >
> > It might take a while though…
> >
> > How about probing VMREAD/VMWRITE to MAX_INDEX in addition to all the known
> > VMCS fields and then checking for equation?
> >
> It can't take that long. VMCS field encodings are only 15 bits, and
> you can ignore the "high" part of 64-bit fields, so that leaves only
> 14 bits.
Unless kvm-unit-tests is being run in L1, in which case things like this
are painful. That being said, I do agree that probing "all" VMCS fields
is the way to go. Walking from highest->lowest probably won't even take
all that many VMREADS. If it is slow, the test can be binned to its own
config.
next prev parent reply other threads:[~2019-12-18 0:24 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-18 16:37 [kvm-unit-tests PATCH] x86: Fix max VMCS field encoding index check Nadav Amit
2019-05-20 14:51 ` Paolo Bonzini
2019-12-12 22:59 ` Jim Mattson
2019-12-13 9:13 ` Nadav Amit
2019-12-13 17:30 ` Jim Mattson
2019-12-18 0:24 ` Sean Christopherson [this message]
2019-12-19 8:52 ` Nadav Amit
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