From: Sean Christopherson <seanjc@google.com>
To: Maxim Levitsky <mlevitsk@redhat.com>
Cc: kvm@vger.kernel.org, pbonzini@redhat.com,
Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Subject: Re: FYI: xapic_state_test selftest fails with avic enabled
Date: Tue, 23 Aug 2022 14:19:05 +0000 [thread overview]
Message-ID: <YwTh2b8ThbiEA7iq@google.com> (raw)
In-Reply-To: <cdbe3d8d07557d73d7a96cd4a69e717574494e34.camel@redhat.com>
On Tue, Aug 23, 2022, Maxim Levitsky wrote:
> Hi!
>
> I just noticed that this test fails when the AVIC is enabled.
>
> It seems that it exposes actual shortcomings in the AVIC hardware implementation,
> although these should not matter in real life usage of it.
>
>
> First of all it seems that AVIC just allows to set the APIC_ICR_BUSY bit (it should be read-only)
> and it never clears it if set.
>
> Second AVIC seems to drop writes to low 24 bits of to ICR2, because these are not really used,
> although technically not marked as reserved in the spec (though APIC_ID register in AMD spec,
> states explicity that only bits 24-31 can be set, and the rest are reserved).
>
> And finally AVIC inhibit when x2apic is exposed to the guest was recently removed,
> because in this case AVIC also works just fine (but with msr emulation) and that
> means that we don't need anymore to hide x2apic from the guest to avoid AVIC inhibit.
KUT's APIC test also fails for a variety of reasons when AVIC is enabled.
https://lore.kernel.org/all/20220204214410.3315068-1-seanjc@google.com
prev parent reply other threads:[~2022-08-23 16:51 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-23 12:57 FYI: xapic_state_test selftest fails with avic enabled Maxim Levitsky
2022-08-23 14:19 ` Sean Christopherson [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YwTh2b8ThbiEA7iq@google.com \
--to=seanjc@google.com \
--cc=kvm@vger.kernel.org \
--cc=mlevitsk@redhat.com \
--cc=pbonzini@redhat.com \
--cc=suravee.suthikulpanit@amd.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.