From: Paolo Bonzini <pbonzini@redhat.com>
To: Liran Alon <liran.alon@oracle.com>
Cc: jmattson@google.com, x86@kernel.org, dwmw@amazon.co.uk,
bp@alien8.de, aliguori@amazon.com, thomas.lendacky@amd.com,
rkrcmar@redhat.com, linux-kernel@vger.kernel.org,
kvm@vger.kernel.org
Subject: Re: [PATCH 3/8] kvm: vmx: pass MSR_IA32_SPEC_CTRL and MSR_IA32_PRED_CMD down to the guest
Date: Tue, 9 Jan 2018 17:57:08 +0100 [thread overview]
Message-ID: <834e9b46-5d59-a81e-8cda-5f576964e1cb@redhat.com> (raw)
In-Reply-To: <222d0a6b-820f-4d7c-a616-ac89f77c3c09@default>
On 09/01/2018 17:48, Liran Alon wrote:
>>>
>>> + if (have_spec_ctrl) {
>>> + rdmsrl(MSR_IA32_SPEC_CTRL, vmx->spec_ctrl);
>>> + if (vmx->spec_ctrl != 0)
>>> + wrmsrl(MSR_IA32_SPEC_CTRL, 0);
>
> As I said also on the AMD patch, I think this is a bug.
> Intel specify that we should set IBRS bit even if it was already set on every #VMExit.
That's correct (though I'd like to understand _why_---I'm not inclined
to blindly trust a spec), but for now it's saving a wrmsr of 0. That is
quite obviously okay, and will be also okay after the bare-metal IBRS
patches.
Of course the code will become something like
if (using_ibrs || vmx->spec_ctrl != 0)
wrmsrl(MSR_IA32_SPEC_CTRL, host_ibrs);
optimizing the case where the host is using retpolines.
Paolo
next prev parent reply other threads:[~2018-01-09 16:57 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-09 16:48 Liran Alon
2018-01-09 16:57 ` Paolo Bonzini [this message]
2018-01-10 5:03 ` Nadav Amit
2018-01-10 13:20 ` Paolo Bonzini
2018-01-10 14:06 ` Arjan van de Ven
2018-01-10 14:28 ` Paolo Bonzini
2018-01-10 15:41 ` Konrad Rzeszutek Wilk
2018-01-10 15:45 ` Paolo Bonzini
2018-01-10 15:48 ` Woodhouse, David
2018-01-10 15:56 ` Paolo Bonzini
2018-01-10 16:05 ` David Woodhouse
2018-01-12 23:17 ` Jim Mattson
2018-01-12 23:19 ` Nadav Amit
-- strict thread matches above, loose matches on Subject: below --
2018-01-10 16:51 Liran Alon
2018-01-10 17:07 ` David Woodhouse
2018-01-10 16:19 Liran Alon
2018-01-10 16:27 ` Paolo Bonzini
2018-01-10 17:14 ` Jim Mattson
2018-01-10 17:16 ` Paolo Bonzini
2018-01-10 17:23 ` Nadav Amit
2018-01-10 17:32 ` Jim Mattson
2018-01-10 16:47 ` David Woodhouse
2018-01-10 0:33 Liran Alon
2018-01-09 16:06 Liran Alon
2018-01-09 12:03 [PATCH v2 0/8] KVM: x86: expose CVE-2017-5715 ("Spectre variant 2") mitigations to guest Paolo Bonzini
2018-01-09 12:03 ` [PATCH 3/8] kvm: vmx: pass MSR_IA32_SPEC_CTRL and MSR_IA32_PRED_CMD down to the guest Paolo Bonzini
2018-01-13 10:16 ` Longpeng (Mike)
2018-01-15 9:23 ` Paolo Bonzini
2018-01-15 9:34 ` Thomas Gleixner
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=834e9b46-5d59-a81e-8cda-5f576964e1cb@redhat.com \
--to=pbonzini@redhat.com \
--cc=aliguori@amazon.com \
--cc=bp@alien8.de \
--cc=dwmw@amazon.co.uk \
--cc=jmattson@google.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=liran.alon@oracle.com \
--cc=rkrcmar@redhat.com \
--cc=thomas.lendacky@amd.com \
--cc=x86@kernel.org \
/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
all inboxes | Powered by JetHome®