From: Wanpeng Li <kernellwp@gmail.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Xiaoyao Li <xiaoyao.li@linux.intel.com>,
Tao Xu <tao3.xu@intel.com>, Radim Krcmar <rkrcmar@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>, kvm <kvm@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] KVM: vmx: Fix the broken usage of vmx_xsaves_supported
Date: Thu, 20 Jun 2019 16:27:26 +0800 [thread overview]
Message-ID: <CANRm+Cy_oo7BkYXD-nc0Ro=rivJircL6aheuFujMv6twS3gk=g@mail.gmail.com> (raw)
In-Reply-To: <b3f76acd-cc7e-9cd7-d7f7-404ba756ab87@redhat.com>
On Thu, 20 Jun 2019 at 16:17, Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 20/06/19 08:46, Xiaoyao Li wrote:
> >>
> >> It depends on whether or not processors support the 1-setting instead
> >> of “enable XSAVES/XRSTORS” is 1 in VM-exection control field. Anyway,
> >
> > Yes, whether this field exist or not depends on whether processors
> > support the 1-setting.
> >
> > But if "enable XSAVES/XRSTORS" is clear to 0, XSS_EXIT_BITMAP doesn't
> > work. I think in this case, there is no need to set this vmcs field?
>
> vmx->secondary_exec_control can change; you are making the code more
> complex by relying on the value of the field at the point of vmx_vcpu_setup.
>
> I do _think_ your version is incorrect, because at this point CPUID has
> not been initialized yet and therefore
> vmx_compute_secondary_exec_control has not set SECONDARY_EXEC_XSAVES.
> However I may be wrong because I didn't review the code very closely:
> the old code is obvious and so there is no point in changing it.
Agreed, in addition, guest can enable/disable cpuid bits by grub
parameter, should we call kvm_x86_ops->cpuid_update() in
kvm_vcpu_reset() path to reflect the new guest cpuid influence to
exec_control? e.g. the first boot guest disable xsaves in grub, kvm
disables xsaves in exec_control; then guest reboot w/ xsaves enabled,
it still get an #UD when executing.
Regards,
Wanpeng Li
next prev parent reply other threads:[~2019-06-20 8:26 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-20 5:03 [PATCH] KVM: vmx: Fix the broken usage of vmx_xsaves_supported Tao Xu
2019-06-20 6:40 ` Wanpeng Li
2019-06-20 6:46 ` Xiaoyao Li
2019-06-20 8:17 ` Paolo Bonzini
2019-06-20 8:27 ` Wanpeng Li [this message]
2019-06-20 8:36 ` Paolo Bonzini
2019-06-20 8:55 ` Xiaoyao Li
2019-06-20 8:59 ` Paolo Bonzini
2019-06-20 9:02 ` Wanpeng Li
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='CANRm+Cy_oo7BkYXD-nc0Ro=rivJircL6aheuFujMv6twS3gk=g@mail.gmail.com' \
--to=kernellwp@gmail.com \
--cc=bp@alien8.de \
--cc=hpa@zytor.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=pbonzini@redhat.com \
--cc=rkrcmar@redhat.com \
--cc=tao3.xu@intel.com \
--cc=tglx@linutronix.de \
--cc=xiaoyao.li@linux.intel.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).