From: Paolo Bonzini <pbonzini@redhat.com>
To: David Woodhouse <dwmw2@infradead.org>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
jmattson@google.com, aliguori@amazon.com,
thomas lendacky <thomas.lendacky@amd.com>,
bp@alien8.de
Subject: Re: [PATCH 3/7] kvm: vmx: pass MSR_IA32_SPEC_CTRL and MSR_IA32_PRED_CMD down to the guest
Date: Mon, 8 Jan 2018 17:33:38 -0500 (EST) [thread overview]
Message-ID: <1441531276.31733151.1515450818280.JavaMail.zimbra@redhat.com> (raw)
In-Reply-To: <1515440467.7317.43.camel@infradead.org>
----- Original Message -----
> From: "David Woodhouse" <dwmw2@infradead.org>
> To: "Paolo Bonzini" <pbonzini@redhat.com>, linux-kernel@vger.kernel.org, kvm@vger.kernel.org
> Cc: jmattson@google.com, aliguori@amazon.com, "thomas lendacky" <thomas.lendacky@amd.com>, bp@alien8.de
> Sent: Monday, January 8, 2018 8:41:07 PM
> Subject: Re: [PATCH 3/7] kvm: vmx: pass MSR_IA32_SPEC_CTRL and MSR_IA32_PRED_CMD down to the guest
>
> On Mon, 2018-01-08 at 19:08 +0100, Paolo Bonzini wrote:
> >
> > + if (have_spec_ctrl && vmx->spec_ctrl != 0)
> > + wrmsrl(MSR_IA32_SPEC_CTRL, vmx->spec_ctrl);
> > +
>
> I think this one probably *is* safe even without an 'else lfence',
> which means that the CPU can speculate around it, but it wants a
> comment explaining that someone has properly analysed it and saying
> precisely why.
This one is okay as long as there are no indirect jumps until
vmresume. But the one on vmexit is only okay because right now
it's *disabling* IBRS. Once IBRS is used by Linux, we'll need an
lfence there. I'll add a comment.
Paolo
next prev parent reply other threads:[~2018-01-08 22:33 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-08 18:08 [PATCH 0/7] KVM: x86: expose CVE-2017-5715 ("Spectre variant 2") mitigations to guest Paolo Bonzini
2018-01-08 18:08 ` [PATCH 1/7] KVM: x86: add SPEC_CTRL and IBPB_SUPPORT accessors Paolo Bonzini
2018-01-08 18:33 ` Konrad Rzeszutek Wilk
2018-01-08 19:09 ` Liran Alon
2018-01-09 10:32 ` Paolo Bonzini
2018-01-09 11:14 ` David Hildenbrand
2018-01-09 11:18 ` Paolo Bonzini
2018-01-08 18:08 ` [PATCH 2/7] x86/msr: add definitions for indirect branch predictor MSRs Paolo Bonzini
2018-01-08 18:35 ` Konrad Rzeszutek Wilk
2018-01-08 18:52 ` Jim Mattson
2018-01-08 19:10 ` Liran Alon
2018-01-08 18:08 ` [PATCH 3/7] kvm: vmx: pass MSR_IA32_SPEC_CTRL and MSR_IA32_PRED_CMD down to the guest Paolo Bonzini
2018-01-08 18:43 ` Konrad Rzeszutek Wilk
2018-01-08 19:18 ` Jim Mattson
2018-01-08 20:23 ` Liran Alon
2018-01-08 22:32 ` Paolo Bonzini
2018-01-08 23:19 ` Jim Mattson
2018-01-09 10:11 ` Paolo Bonzini
2018-01-08 19:22 ` Liran Alon
2018-01-08 19:41 ` David Woodhouse
2018-01-08 22:33 ` Paolo Bonzini [this message]
2018-01-08 22:09 ` Ashok Raj
2018-01-08 22:25 ` Paolo Bonzini
2018-01-11 2:47 ` Tim Chen
2018-01-11 10:41 ` Paolo Bonzini
2018-01-08 18:08 ` [PATCH 4/7] kvm: vmx: Set IBPB when running a different VCPU Paolo Bonzini
2018-01-08 19:23 ` Liran Alon
2018-01-08 19:36 ` Jim Mattson
2018-01-09 8:33 ` Paolo Bonzini
2018-01-09 11:01 ` David Hildenbrand
2018-01-08 18:08 ` [PATCH 5/7] kvm: svm: pass MSR_IA32_SPEC_CTRL and MSR_IA32_PRED_CMD down to guest Paolo Bonzini
2018-01-08 19:41 ` Liran Alon
2018-01-08 18:08 ` [PATCH 6/7] x86/svm: Set IBPB when running a different VCPU Paolo Bonzini
2018-01-08 20:00 ` Liran Alon
2018-01-09 11:07 ` Paolo Bonzini
2018-01-08 18:08 ` [PATCH 7/7] KVM: x86: add SPEC_CTRL and IBPB_SUPPORT to MSR and CPUID lists Paolo Bonzini
2018-01-08 20:07 ` Liran Alon
2018-01-08 20:15 ` Jim Mattson
2018-01-09 10:15 ` [PATCH 0/7] KVM: x86: expose CVE-2017-5715 ("Spectre variant 2") mitigations to guest Thomas Gleixner
2018-01-09 11:12 ` Paolo Bonzini
2018-01-09 12:03 ` Thomas Gleixner
2018-01-09 14:06 ` Paolo Bonzini
-- strict thread matches above, loose matches on Subject: below --
2018-01-08 23:58 [PATCH 3/7] kvm: vmx: pass MSR_IA32_SPEC_CTRL and MSR_IA32_PRED_CMD down to the guest Liran Alon
2018-01-09 8:35 ` Paolo Bonzini
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=1441531276.31733151.1515450818280.JavaMail.zimbra@redhat.com \
--to=pbonzini@redhat.com \
--cc=aliguori@amazon.com \
--cc=bp@alien8.de \
--cc=dwmw2@infradead.org \
--cc=jmattson@google.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=thomas.lendacky@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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox