From: "Jan Beulich" <JBeulich@suse.com>
To: Shuai Ruan <shuai.ruan@linux.intel.com>
Cc: andrew.cooper3@citrix.com, keir@xen.org, xen-devel@lists.xen.org
Subject: Re: [V5] x86/xsaves: fix overwriting between non-lazy/lazy xsaves
Date: Wed, 23 Mar 2016 04:21:32 -0600 [thread overview]
Message-ID: <56F27C3C02000078000DF90A@prv-mh.provo.novell.com> (raw)
In-Reply-To: <20160323061455.GA12388@shuai.ruan@linux.intel.com>
>>> On 23.03.16 at 07:14, <shuai.ruan@linux.intel.com> wrote:
> On Wed, Mar 23, 2016 at 10:02:24AM +0800, Shuai Ruan wrote:
> But for hvm_vcpu_reset_state(), I think we should deleting the code
> initializing the xcomp_bv as said below.
>> For hvm_vcpu_reset_state(), we should depend on whether xsaves is used
>> to decide whether to init xcomp_bv or not. And currently we use
>> xcr0_accum to indicate the use of xsaves, when hvm_vcpu_reset_state()
>> is called , can vcpu->xcr0_accum indicate using of xsaves ?
>> I think in hvm_vcpu_reset_state(), we should leave xcomp_bv zero.
Leaving it to be zero would be fine, but is it guaranteed to be
zero?
>> > Since again you repeat the same logic twice, this should again have
>> > been a signal that all your changes should go into the XRSTOR()
>> > macro. Or alternatively, since the exception fixup also differs, you
>> > may want to convert the whole logic into an XSAVES and an XSAVE
>> > path. My only really sincere request here is - as little redundancy as
>> > possible, since having to change the same thing twice in more than
>> > one place is always calling for trouble.
> I will do all changes only in XRSTOR(). Code like :
>
> #define _XRSTOR(pfx, xrstor_ins)
> asm volatile ( "1: .byte " pfx xrstor_ins"\n" \
> "3:\n" \
> " .section .fixup,\"ax\"\n" \
> "2: incl %[faults]\n" \
> " jmp 3b\n" \
> " .previous\n" \
> _ASM_EXTABLE(1b, 2b) \
> : [mem] "+m" (*ptr), [faults] "+g" (faults) \
> : [lmask] "a" (lmask), [hmask] "d" (hmask), \
> [ptr] "D" (ptr) )
>
> #define XRSTOR(pfx) \
> if ( v->arch.xcr0_accum & XSTATE_XSAVES_ONLY ) \
> { \
> if ( unlikely(!(ptr->xsave_hdr.xcomp_bv \
> & XSTATE_COMPACTION_ENABLED)) ) \
> ptr->xsave_hdr.xcomp_bv |= (ptr->xsave_hdr.xstate_bv \
> | XSTATE_COMPACTION_ENABLED); \
> _XRSTOR("0x48, ", "0x0f,0xc7,0x1f"); \
I think you mean to use pfx here. Also I don't see the point of
passing two string literals to the auxiliary macro - just pass them
as a single argument.
> A now wapper is intruduced as "_XRSTOR"( maybe the macro name is not
> good ).
Indeed an underscore followed by an uppercase letter is starting
a reserved identifier. Maybe DO_XRSTOR() or _xrstor()?
Jan
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel
next prev parent reply other threads:[~2016-03-23 10:21 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-18 3:01 [V5] x86/xsaves: fix overwriting between non-lazy/lazy xsaves Shuai Ruan
2016-03-22 14:34 ` Jan Beulich
2016-03-23 2:02 ` Shuai Ruan
[not found] ` <20160323020224.GB4131@shuai.ruan@linux.intel.com>
2016-03-23 6:14 ` Shuai Ruan
[not found] ` <20160323061455.GA12388@shuai.ruan@linux.intel.com>
2016-03-23 10:21 ` Jan Beulich [this message]
2016-03-23 11:01 ` Shuai Ruan
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=56F27C3C02000078000DF90A@prv-mh.provo.novell.com \
--to=jbeulich@suse.com \
--cc=andrew.cooper3@citrix.com \
--cc=keir@xen.org \
--cc=shuai.ruan@linux.intel.com \
--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).