All of
 help / color / mirror / Atom feed
From: Xiaoyao Li <>
To: Paolo Bonzini <>,
	Sean Christopherson <>
Cc: "Radim Krčmář" <>,
	"Thomas Gleixner" <>,
	"Ingo Molnar" <>,
	"Borislav Petkov" <>,
	"H. Peter Anvin" <>,,,
Subject: Re: [PATCH] kvm/x86/vmx: Make the emulation of MSR_IA32_ARCH_CAPABILITIES only for vmx
Date: Fri, 08 Mar 2019 09:53:14 +0800	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Thu, 2019-03-07 at 19:15 +0100, Paolo Bonzini wrote:
> On 07/03/19 18:37, Sean Christopherson wrote:
> > On Thu, Mar 07, 2019 at 05:31:43PM +0800, Xiaoyao Li wrote:
> > > At present, we report F(ARCH_CAPABILITIES) for x86 arch(both vmx and svm)
> > > unconditionally, but we only emulate this MSR in vmx. It will cause #GP
> > > while guest kernel rdmsr(MSR_IA32_ARCH_CAPABILITIES) in an AMD host.
> > > 
> > > Since MSR IA32_ARCH_CAPABILITIES is an intel-specific MSR, it makes no
> > > sense to emulate it in svm. Thus this patch chooses to only emulate it
> > > for vmx, and moves the related handling to vmx related files.
> > 
> > What about emulating the MSR on an AMD host for testing purpsoes?  It
> > might be a useful way for someone without Intel hardware to test spectre
> > related flows.
> > 
> > In other words, an alternative to restricting emulation of the MSR to
> > Intel CPUS would be to move MSR_IA32_ARCH_CAPABILITIES handling into
> > kvm_{get,set}_msr_common().  Guest access to MSR_IA32_ARCH_CAPABILITIES
> > is gated by X86_FEATURE_ARCH_CAPABILITIES in the guest's CPUID, e.g.
> > RDMSR will naturally #GP fault if userspace passes through the host's
> > CPUID on a non-Intel system.
> This is also better because it wouldn't change the guest ABI for AMD
> processors.  Dropping CPUID flags is generally not a good idea.
> Paolo

Hi, Paolo and Sean,

OK, as you think it's better to emulate MSR ARCH_CAPABILITIES on all x86 host,
so should I make the same to MSR CORE_CAPABILITY?

If so, I will make it for our v5 patches of split lock detection to emualte MSR
CORE_CAPABILITY in this way.


      reply	other threads:[~2019-03-08  1:56 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-07  9:31 [PATCH] kvm/x86/vmx: Make the emulation of MSR_IA32_ARCH_CAPABILITIES only for vmx Xiaoyao Li
     [not found] ` <>
2019-03-07 18:15   ` Paolo Bonzini
2019-03-08  1:53     ` Xiaoyao Li [this message]

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:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \ \ \ \ \ \ \ \

* 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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.