From: Joerg Roedel <joro@8bytes.org>
To: Bandan Das <bsd@redhat.com>
Cc: "Paolo Bonzini" <pbonzini@redhat.com>,
kvm@vger.kernel.org, "Dirk Müller" <dmueller@suse.com>
Subject: Re: [PATCH] Use WARN_ON_ONCE for missing X86_FEATURE_NRIPS
Date: Tue, 6 Oct 2015 12:28:38 +0200 [thread overview]
Message-ID: <20151006102838.GD20886@8bytes.org> (raw)
In-Reply-To: <jpgbncixlts.fsf@linux.bootlegged.copy>
On Thu, Oct 01, 2015 at 06:31:27PM -0400, Bandan Das wrote:
> >> @@ -514,7 +514,7 @@ static void skip_emulated_instruction(struct kvm_vcpu *vcpu)
> >> struct vcpu_svm *svm = to_svm(vcpu);
> >>
> >> if (svm->vmcb->control.next_rip != 0) {
> >> - WARN_ON(!static_cpu_has(X86_FEATURE_NRIPS));
> >> + WARN_ON_ONCE(!static_cpu_has(X86_FEATURE_NRIPS));
> >> svm->next_rip = svm->vmcb->control.next_rip;
> >> }
I looked again how this could possibly be triggered, and I am somewhat
confused now.
So svm->vmcb->control.next_rip is only written by hardware or in
svm_check_intercept(). Both cases write only to this field, if the
hardware supports X86_FEATURE_NRIPS. The write in nested_svm_vmexit only
targets the guests VMCB, and we don't use that one again.
So I can't see how the WARN_ON above could be triggered. Do I miss
something or might this also be a miscompilation of static_cpu_has?
Joerg
next prev parent reply other threads:[~2015-10-06 10:28 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-01 11:43 [PATCH] Use WARN_ON_ONCE for missing X86_FEATURE_NRIPS Dirk Müller
2015-10-01 12:25 ` Paolo Bonzini
2015-10-01 12:45 ` Dirk Müller
2015-10-01 12:31 ` Paolo Bonzini
2015-10-01 22:31 ` Bandan Das
2015-10-02 6:43 ` Dirk Müller
2015-10-05 1:15 ` Bandan Das
2015-10-05 9:50 ` Joerg Roedel
2015-10-05 16:54 ` Bandan Das
2015-10-05 17:15 ` Joerg Roedel
2015-10-05 17:42 ` Bandan Das
2015-10-06 10:23 ` Joerg Roedel
2015-10-06 18:02 ` Bandan Das
2015-10-05 20:12 ` Dirk Müller
2015-10-05 22:00 ` Bandan Das
2015-10-06 10:28 ` Joerg Roedel [this message]
2015-10-06 17:59 ` Bandan Das
2015-10-07 11:03 ` Joerg Roedel
2015-10-07 12:47 ` [PATCH] kvm: svm: Only propagate next_rip when guest supports it Joerg Roedel
2015-10-07 12:57 ` kbuild test robot
2015-10-07 15:48 ` Bandan Das
2015-10-07 16:14 ` Joerg Roedel
2015-10-07 17:03 ` Dirk Müller
2015-10-07 14:58 ` [PATCH] Use WARN_ON_ONCE for missing X86_FEATURE_NRIPS Bandan Das
2015-10-07 15:24 ` Joerg Roedel
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=20151006102838.GD20886@8bytes.org \
--to=joro@8bytes.org \
--cc=bsd@redhat.com \
--cc=dmueller@suse.com \
--cc=kvm@vger.kernel.org \
--cc=pbonzini@redhat.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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).