From: Paolo Bonzini <pbonzini@redhat.com>
To: Sean Christopherson <seanjc@google.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Michael Kelley <mhklinux@outlook.com>,
Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Xi Ruoyao <xry111@xry111.site>
Subject: Re: [RFC PATCH] KVM: x86: Advertise PCID based on hardware support (with an asterisk)
Date: Thu, 11 Apr 2024 18:36:46 +0200 [thread overview]
Message-ID: <bd8e7f8b-532f-4372-a3fd-69893e359b42@redhat.com> (raw)
In-Reply-To: <20240411163130.1809713-1-seanjc@google.com>
On 4/11/24 18:31, Sean Christopherson wrote:
> Force set a synthetic feature, GUEST_PCID, if PCID can be safely used in
> virtual machines, even if the kernel itself disables PCID support, and
> advertise PCID support in KVM if GUEST_PCID is set.
>
> When running on a CPU that is affected by Intel's "Global INVLPG" erratum,
> which does NOT affect VMX non-root mode, it is safe to virtualize PCID for
> KVM guests, even though it is not safe for the kernel itself to enable PCID.
> Ditto for if the kernel disables PCID because CR4.PGE isn't supported.
But the guest would not use it if the f/m/s matches, right? If the
advantage is basically not splitting the migration pool, is that a
concern for the affected Alder Lake/Gracemont/Raptor Lake processors?
Paolo
next prev parent reply other threads:[~2024-04-11 16:36 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-11 16:31 [RFC PATCH] KVM: x86: Advertise PCID based on hardware support (with an asterisk) Sean Christopherson
2024-04-11 16:36 ` Paolo Bonzini [this message]
2024-04-11 19:11 ` Sean Christopherson
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=bd8e7f8b-532f-4372-a3fd-69893e359b42@redhat.com \
--to=pbonzini@redhat.com \
--cc=andrew.cooper3@citrix.com \
--cc=bp@alien8.de \
--cc=dave.hansen@linux.intel.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@kernel.org \
--cc=mhklinux@outlook.com \
--cc=mingo@redhat.com \
--cc=pawan.kumar.gupta@linux.intel.com \
--cc=peterz@infradead.org \
--cc=seanjc@google.com \
--cc=tglx@linutronix.de \
--cc=x86@kernel.org \
--cc=xry111@xry111.site \
/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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox