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: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-11 9:23 [Qemu-devel] [PATCH][uq/master] kvm: x86: Save/restore FPU OP, IP and DP Jan Kiszka
2011-06-13 8:45 ` Avi Kivity
2011-06-14 6:10 ` Jan Kiszka
2011-06-14 8:23 ` Avi Kivity
2011-06-14 8:28 ` Jan Kiszka
2011-06-15 9:10 ` Avi Kivity
2011-06-15 10:20 ` Jan Kiszka
2011-06-15 10:39 ` Jan Kiszka
2011-06-15 11:26 ` Avi Kivity [this message]
2011-06-15 11:32 ` Jan Kiszka
2011-06-15 11:33 ` Avi Kivity
2011-06-15 11:45 ` Jan Kiszka
2011-06-15 13:17 ` [Qemu-devel] [PATCH v2][uq/master] " Jan Kiszka
2011-06-16 9:42 ` Christophe Fergeau
2011-06-19 12:58 ` Avi Kivity
2011-06-16 9:35 ` [Qemu-devel] [PATCH][uq/master] " Christophe Fergeau
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