From: Eduardo Habkost <ehabkost@redhat.com>
To: Jim Mattson <jmattson@google.com>
Cc: "Gerd Hoffmann" <kraxel@redhat.com>,
"Daniel P. Berrangé" <berrange@redhat.com>,
mtosatti@redhat.com,
"Pedro Principeza" <pedro.principeza@canonical.com>,
"kvm list" <kvm@vger.kernel.org>,
libvir-list@redhat.com,
"Dann Frazier" <dann.frazier@canonical.com>,
"Guilherme Piccoli" <gpiccoli@canonical.com>,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
"Christian Ehrhardt" <christian.ehrhardt@canonical.com>,
qemu-devel@nongnu.org, "Paolo Bonzini" <pbonzini@redhat.com>,
"Mohammed Gamal" <mgamal@redhat.com>,
"Laszlo Ersek" <lersek@redhat.com>,
fw@gpiccoli.net, rth@twiddle.net
Subject: Re: [PATCH 2/2] x86/cpu: Handle GUEST_MAXPHYADDR < HOST_MAXPHYADDR for hosts that don't support it
Date: Thu, 9 Jul 2020 15:13:07 -0400 [thread overview]
Message-ID: <20200709191307.GH780932@habkost.net> (raw)
In-Reply-To: <CALMp9eQnrdu-9sZhW3aXpK4pizOW=8G=bj1wkumSgHVNfG=CbQ@mail.gmail.com>
On Thu, Jul 09, 2020 at 10:00:59AM -0700, Jim Mattson wrote:
> On Thu, Jul 9, 2020 at 2:44 AM Gerd Hoffmann <kraxel@redhat.com> wrote:
>
> > (2) GUEST_MAXPHYADDR < HOST_MAXPHYADDR
> >
> > Mostly fine. Some edge cases, like different page fault errors for
> > addresses above GUEST_MAXPHYADDR and below HOST_MAXPHYADDR. Which I
> > think Mohammed fixed in the kernel recently.
>
> Doesn't this require intercepting MOV-to-CR3 when the guest is in PAE
> mode, so that the hypervisor can validate the high bits in the PDPTEs?
If the fix has additional overhead, is the additional overhead
bad enough to warrant making it optional? Most existing
GUEST_MAXPHYADDR < HOST_MAXPHYADDR guests already work today
without the fix.
--
Eduardo
next prev parent reply other threads:[~2020-07-09 19:13 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-19 15:53 [PATCH 0/2] kvm: x86/cpu: Support guest MAXPHYADDR < host MAXPHYADDR Mohammed Gamal
2020-06-19 15:53 ` [PATCH 1/2] kvm: Add support for KVM_CAP_HAS_SMALLER_MAXPHYADDR Mohammed Gamal
2020-06-19 15:53 ` [PATCH 2/2] x86/cpu: Handle GUEST_MAXPHYADDR < HOST_MAXPHYADDR for hosts that don't support it Mohammed Gamal
2020-06-19 16:25 ` Paolo Bonzini
2020-07-08 17:16 ` Eduardo Habkost
2020-07-08 17:26 ` Daniel P. Berrangé
2020-07-09 9:44 ` Gerd Hoffmann
2020-07-09 9:55 ` Mohammed Gamal
2020-07-09 10:11 ` Paolo Bonzini
2020-07-09 17:00 ` Jim Mattson
2020-07-09 19:13 ` Eduardo Habkost [this message]
2020-07-10 7:22 ` Paolo Bonzini
2020-07-10 16:02 ` Eduardo Habkost
2020-07-10 16:49 ` Paolo Bonzini
2020-07-10 7:21 ` Paolo Bonzini
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