From: Sean Christopherson <seanjc@google.com>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Jing Liu <jing2.liu@linux.intel.com>,
pbonzini@redhat.com, Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1] kvm: x86: Revise guest_fpu xcomp_bv field
Date: Mon, 8 Feb 2021 09:24:30 -0800 [thread overview]
Message-ID: <YCFzztFESzcnKRqQ@google.com> (raw)
In-Reply-To: <4e4b37d1-e2f8-6757-003c-d19ae8184088@intel.com>
On Mon, Feb 08, 2021, Dave Hansen wrote:
> On 2/8/21 8:16 AM, Jing Liu wrote:
> > -#define XSTATE_COMPACTION_ENABLED (1ULL << 63)
> > -
> > static void fill_xsave(u8 *dest, struct kvm_vcpu *vcpu)
> > {
> > struct xregs_state *xsave = &vcpu->arch.guest_fpu->state.xsave;
> > @@ -4494,7 +4492,8 @@ static void load_xsave(struct kvm_vcpu *vcpu, u8 *src)
> > /* Set XSTATE_BV and possibly XCOMP_BV. */
> > xsave->header.xfeatures = xstate_bv;
> > if (boot_cpu_has(X86_FEATURE_XSAVES))
> > - xsave->header.xcomp_bv = host_xcr0 | XSTATE_COMPACTION_ENABLED;
> > + xsave->header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT |
> > + xfeatures_mask_all;
This is wrong, xfeatures_mask_all also tracks supervisor states.
> Are 'host_xcr0' and 'xfeatures_mask_all' really interchangeable? If so,
> shouldn't we just remove 'host_xcr0' everywhere?
I think so? But use xfeatures_mask_user().
In theory, host_xss can also be replaced with the _supervisor() and _dynamic()
variants. That code needs a good hard look at the _dynamic() features, which is
currently just architectural LBRs. E.g. I wouldn't be surprised if KVM currently
fails to save/restore arch LBRs due to the bit not being set in host_xss.
next prev parent reply other threads:[~2021-02-08 17:27 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-08 16:16 [PATCH v1] kvm: x86: Revise guest_fpu xcomp_bv field Jing Liu
2021-02-08 15:23 ` Dave Hansen
2021-02-08 17:24 ` Sean Christopherson [this message]
2021-02-22 3:21 ` Liu, Jing2
2021-02-22 16:06 ` Sean Christopherson
2021-02-23 3:06 ` Liu, Jing2
2021-02-24 20:40 ` Sean Christopherson
2021-02-25 2:02 ` Liu, Jing2
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=YCFzztFESzcnKRqQ@google.com \
--to=seanjc@google.com \
--cc=bp@alien8.de \
--cc=dave.hansen@intel.com \
--cc=hpa@zytor.com \
--cc=jing2.liu@linux.intel.com \
--cc=jmattson@google.com \
--cc=joro@8bytes.org \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=pbonzini@redhat.com \
--cc=tglx@linutronix.de \
--cc=vkuznets@redhat.com \
--cc=wanpengli@tencent.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