From: Shuai Ruan <shuai.ruan@linux.intel.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: andrew.cooper3@citrix.com, keir@xen.org, xen-devel@lists.xen.org
Subject: Re: [PATCH V7 3/3] x86/xsaves: ebx may return wrong value using CPUID eax=0xdh, ecx =1
Date: Wed, 6 Apr 2016 15:01:01 +0800 [thread overview]
Message-ID: <3306.7504097291$1459925986@news.gmane.org> (raw)
In-Reply-To: <5703940C02000078000E3105@prv-mh.provo.novell.com>
On Tue, Apr 05, 2016 at 02:31:40AM -0600, Jan Beulich wrote:
> >>> On 31.03.16 at 10:57, <shuai.ruan@linux.intel.com> wrote:
> > Refer to SDM 13.4.3 Extended Region of an XSAVE Area. The value return
>
> No section numbers please - they tend to change.
>
> > by ecx[1] with cpuid function 0xdh and sub-fucntion i (i>1) indicates
>
> Either "0xd" or "0dh". And "function".
>
> > --- a/xen/arch/x86/traps.c
> > +++ b/xen/arch/x86/traps.c
> > @@ -1020,6 +1020,18 @@ void pv_cpuid(struct cpu_user_regs *regs)
> > a &= (boot_cpu_data.x86_capability[cpufeat_word(X86_FEATURE_XSAVEOPT)] &
> > ~cpufeat_mask(X86_FEATURE_XSAVES));
> > b = c = d = 0;
> > + if ( cpu_has_xsavec )
> > + {
> > + b = XSTATE_AREA_MIN_SIZE;
>
> Is this really correct namely when curr->arch.xcr0 == 0? If not, the
> if() below should perhaps be combined with the if() above (and then
> the same would apply to hvm_cpuid()).
>
> > + if ( curr->arch.xcr0 )
> > + for( subleaf = 2; subleaf < 63; subleaf++ )
> > + if ( (1ULL << subleaf) & curr->arch.xcr0 )
>
> The first if() is redundant with this second one. If you really
> mean to avoid the loop, then please also only check bits
> 2..62 in the first if().
>
Ok for all comments above.
Another question is whether we should add this in pv_cpuid() or not.
(which we have discussed in the previous thread).
Refer to SDM Volume 1
"13.2 ENUMERATION OF CPU SUPPORT FOR XSAVE INSTRUCTIONS AND XSAVE-
SUPPORTED FEATURES"
— CPUID function 0DH, sub-function 1.
...
"EBX enumerates the size (in bytes) required by the XSAVES instruction
for an XSAVE area containing all
the state components corresponding to bits currently set in XCR0 |
IA32_XSS."
From the descriptions above, EBX only be used when XSAVES is enabled.
So I think we should not deal with pv_cpuid() here.
Any comments ?
> Jan
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org
> http://lists.xen.org/xen-devel
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel
next prev parent reply other threads:[~2016-04-06 7:01 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-31 8:57 [PATCH V7 0/3] xsaves bug fix Shuai Ruan
2016-03-31 8:57 ` [PATCH V7 1/3] x86/xsaves: fix overwriting between non-lazy/lazy xsaves Shuai Ruan
2016-04-04 15:51 ` Jan Beulich
2016-04-05 5:30 ` Shuai Ruan
[not found] ` <20160405053023.GA16876@shuai.ruan@linux.intel.com>
2016-04-05 7:17 ` Jan Beulich
2016-04-05 7:29 ` Shuai Ruan
2016-04-25 6:51 ` Jan Beulich
2016-04-29 1:36 ` Shuai Ruan
[not found] ` <20160429013616.GB4359@shuai.ruan@linux.intel.com>
2016-04-29 7:05 ` Jan Beulich
2016-03-31 8:57 ` [PATCH V7 2/3] x86/xsaves: fix two remained issues Shuai Ruan
2016-04-04 16:03 ` Jan Beulich
2016-03-31 8:57 ` [PATCH V7 3/3] x86/xsaves: ebx may return wrong value using CPUID eax=0xdh, ecx =1 Shuai Ruan
2016-04-05 8:31 ` Jan Beulich
2016-04-06 7:01 ` Shuai Ruan [this message]
[not found] ` <20160406070034.GA26357@shuai.ruan@linux.intel.com>
2016-04-07 0:29 ` Jan Beulich
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='3306.7504097291$1459925986@news.gmane.org' \
--to=shuai.ruan@linux.intel.com \
--cc=JBeulich@suse.com \
--cc=andrew.cooper3@citrix.com \
--cc=keir@xen.org \
--cc=xen-devel@lists.xen.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).