From: Paolo Bonzini <pbonzini@redhat.com>
To: Borislav Petkov <bp@alien8.de>, Eduardo Habkost <ehabkost@redhat.com>
Cc: "Jörg Rödel" <joro@8bytes.org>,
"Andre Przywara" <andre.przywara@arm.com>,
"kvm ML" <kvm@vger.kernel.org>,
lkml <linux-kernel@vger.kernel.org>
Subject: Re: kvm: RDTSCP on AMD
Date: Wed, 6 Jul 2016 15:01:04 +0200 [thread overview]
Message-ID: <b7e01819-f604-7e2b-fd6d-6323bd05587e@redhat.com> (raw)
In-Reply-To: <20160706124438.GB7300@pd.tnic>
On 06/07/2016 14:44, Borislav Petkov wrote:
> Hi guys,
>
> how about this below to enable RDTSCP emulation on AMD? IOW, I'm staring
> at
>
> 33b5e8c03ae7 ("target-i386: Disable rdtscp on Opteron_G* CPU models")
>
> in the qemu repo.
>
> It seems to work here, RDTSCP in the guest gives me node and cpu as
> vsyscall_set_cpu() in the guest kernel has set them.
>
> Thoughts?
>
> (Below is the simple qemu diff reenabling RDTSCP)
>
> @@ -3919,6 +3935,7 @@ static int (*const svm_exit_handlers[])(struct vcpu_svm *svm) = {
> [SVM_EXIT_STGI] = stgi_interception,
> [SVM_EXIT_CLGI] = clgi_interception,
> [SVM_EXIT_SKINIT] = skinit_interception,
> + [SVM_EXIT_RDTSCP] = rdtscp_interception,
> [SVM_EXIT_WBINVD] = wbinvd_interception,
> [SVM_EXIT_MONITOR] = monitor_interception,
> [SVM_EXIT_MWAIT] = mwait_interception,
Nothing is needed in the kernel actually. You can skip the intercept
by running the guest with MSR_TSC_AUX set to the guest's expected value.
Which KVM does, except that it's botched so I need to apply the
patch in https://lkml.org/lkml/2016/4/13/802.
> ---
>
> qemu diff:
>
> ---
> diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> index 3bd3cfc3ad16..aa6d0d027d00 100644
> --- a/target-i386/cpu.c
> +++ b/target-i386/cpu.c
This is not enough because it's missing some backwards compatibility
gunk (similar to the include/hw/i386/pc.h parts of 33b5e8c03ae), but
it's enough for a proof of concept and to discuss it.
The main issue with this is that it would force a lockstep update of
QEMU and kernel, which we try to avoid. I'm not sure if we have a
solution for this problem. Eduardo?
Paolo
next prev parent reply other threads:[~2016-07-06 13:01 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-06 12:44 kvm: RDTSCP on AMD Borislav Petkov
2016-07-06 13:01 ` Paolo Bonzini [this message]
2016-07-06 17:34 ` Eduardo Habkost
2016-07-06 21:27 ` Paolo Bonzini
2018-12-10 18:13 Borislav Petkov
2018-12-10 18:37 ` Eduardo Habkost
2018-12-10 18:41 ` Borislav Petkov
2018-12-10 19:06 ` Eduardo Habkost
2018-12-10 19:42 ` Borislav Petkov
2018-12-10 20:08 ` Eduardo Habkost
2018-12-10 20:39 ` Borislav Petkov
2018-12-11 10:38 ` Daniel P. Berrangé
2018-12-11 11:55 ` Eduardo Habkost
2018-12-11 14:35 ` Daniel P. Berrangé
2018-12-11 15:23 ` Paolo Bonzini
2018-12-11 15:30 ` Daniel P. Berrangé
2018-12-10 19:47 ` Eduardo Habkost
2018-12-10 20:16 ` Borislav Petkov
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=b7e01819-f604-7e2b-fd6d-6323bd05587e@redhat.com \
--to=pbonzini@redhat.com \
--cc=andre.przywara@arm.com \
--cc=bp@alien8.de \
--cc=ehabkost@redhat.com \
--cc=joro@8bytes.org \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.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;
as well as URLs for NNTP newsgroup(s).