From: Avi Kivity <avi@redhat.com>
To: Jan Kiszka <jan.kiszka@web.de>
Cc: Marcelo Tosatti <mtosatti@redhat.com>, kvm <kvm@vger.kernel.org>,
qemu-devel <qemu-devel@nongnu.org>,
Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>,
Christophe Fergeau <cfergeau@redhat.com>
Subject: Re: [PATCH][uq/master] kvm: x86: Save/restore FPU OP, IP and DP
Date: Wed, 15 Jun 2011 14:26:16 +0300 [thread overview]
Message-ID: <4DF896D8.2000506@redhat.com> (raw)
In-Reply-To: <4DF88773.3050401@web.de>
On 06/15/2011 01:20 PM, Jan Kiszka wrote:
> >
> > So fopcode will usually be clear.
> >
>
> OK. So if bit 2 of IA32_MISC_ENABLE MSR, we must save that fields. But
> if it's off, how to test for that other condition "last non-transparent
> FP instruction ... had an unmasked exception" from the host?
>
We save fopcode unconditionally. But if IA32_MISC_ENABLE_MSR[2]=0, then
fopcode will be zero, and we can skip the subsection (if the data and
instruction pointers are also zero, which they will be).
If it isn't zero, there's still a good chance fopcode will be zero
(64-bit userspace, thread that hasn't used the fpu since the last
context switch, last opcode happened to be zero).
--
error compiling committee.c: too many arguments to function
WARNING: multiple messages have this Message-ID (diff)
From: Avi Kivity <avi@redhat.com>
To: Jan Kiszka <jan.kiszka@web.de>
Cc: Christophe Fergeau <cfergeau@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
qemu-devel <qemu-devel@nongnu.org>, kvm <kvm@vger.kernel.org>,
Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Subject: Re: [Qemu-devel] [PATCH][uq/master] kvm: x86: Save/restore FPU OP, IP and DP
Date: Wed, 15 Jun 2011 14:26:16 +0300 [thread overview]
Message-ID: <4DF896D8.2000506@redhat.com> (raw)
In-Reply-To: <4DF88773.3050401@web.de>
On 06/15/2011 01:20 PM, Jan Kiszka wrote:
> >
> > So fopcode will usually be clear.
> >
>
> OK. So if bit 2 of IA32_MISC_ENABLE MSR, we must save that fields. But
> if it's off, how to test for that other condition "last non-transparent
> FP instruction ... had an unmasked exception" from the host?
>
We save fopcode unconditionally. But if IA32_MISC_ENABLE_MSR[2]=0, then
fopcode will be zero, and we can skip the subsection (if the data and
instruction pointers are also zero, which they will be).
If it isn't zero, there's still a good chance fopcode will be zero
(64-bit userspace, thread that hasn't used the fpu since the last
context switch, last opcode happened to be zero).
--
error compiling committee.c: too many arguments to function
next prev parent reply other threads:[~2011-06-15 11:26 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-11 9:23 [PATCH][uq/master] kvm: x86: Save/restore FPU OP, IP and DP Jan Kiszka
2011-06-11 9:23 ` [Qemu-devel] " Jan Kiszka
2011-06-13 8:45 ` Avi Kivity
2011-06-13 8:45 ` [Qemu-devel] " Avi Kivity
2011-06-14 6:10 ` Jan Kiszka
2011-06-14 6:10 ` [Qemu-devel] " Jan Kiszka
2011-06-14 8:23 ` Avi Kivity
2011-06-14 8:23 ` [Qemu-devel] " Avi Kivity
2011-06-14 8:28 ` Jan Kiszka
2011-06-14 8:28 ` [Qemu-devel] " Jan Kiszka
2011-06-15 9:10 ` Avi Kivity
2011-06-15 9:10 ` [Qemu-devel] " Avi Kivity
2011-06-15 10:20 ` Jan Kiszka
2011-06-15 10:20 ` [Qemu-devel] " Jan Kiszka
2011-06-15 10:39 ` Jan Kiszka
2011-06-15 10:39 ` [Qemu-devel] " Jan Kiszka
2011-06-15 11:26 ` Avi Kivity [this message]
2011-06-15 11:26 ` Avi Kivity
2011-06-15 11:32 ` Jan Kiszka
2011-06-15 11:32 ` [Qemu-devel] " Jan Kiszka
2011-06-15 11:33 ` Avi Kivity
2011-06-15 11:33 ` [Qemu-devel] " Avi Kivity
2011-06-15 11:45 ` Jan Kiszka
2011-06-15 11:45 ` [Qemu-devel] " Jan Kiszka
2011-06-15 13:17 ` [PATCH v2][uq/master] " Jan Kiszka
2011-06-15 13:17 ` [Qemu-devel] " Jan Kiszka
2011-06-16 9:42 ` Christophe Fergeau
2011-06-16 9:42 ` Christophe Fergeau
2011-06-19 12:58 ` Avi Kivity
2011-06-19 12:58 ` [Qemu-devel] " Avi Kivity
2011-06-16 9:35 ` [PATCH][uq/master] " Christophe Fergeau
2011-06-16 9:35 ` [Qemu-devel] " Christophe Fergeau
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=4DF896D8.2000506@redhat.com \
--to=avi@redhat.com \
--cc=cfergeau@redhat.com \
--cc=jan.kiszka@web.de \
--cc=kvm@vger.kernel.org \
--cc=mtosatti@redhat.com \
--cc=qemu-devel@nongnu.org \
--cc=stefanha@linux.vnet.ibm.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 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.