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Re: [Qemu-devel] [PATCH][uq/master] kvm: x86: Save/restore FPU OP, IP an
From: |
Jan Kiszka |
Subject: |
Re: [Qemu-devel] [PATCH][uq/master] kvm: x86: Save/restore FPU OP, IP and DP |
Date: |
Wed, 15 Jun 2011 13:32:11 +0200 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 |
On 2011-06-15 13:26, Avi Kivity wrote:
> 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).
I do not yet find "if fopcode is invalid, it is zero, just as IP and DP"
in the spec. What clears them reliably?
Jan
--
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux
- [Qemu-devel] [PATCH][uq/master] kvm: x86: Save/restore FPU OP, IP and DP, Jan Kiszka, 2011/06/11
- Re: [Qemu-devel] [PATCH][uq/master] kvm: x86: Save/restore FPU OP, IP and DP, Avi Kivity, 2011/06/13
- Re: [Qemu-devel] [PATCH][uq/master] kvm: x86: Save/restore FPU OP, IP and DP, Jan Kiszka, 2011/06/14
- Re: [Qemu-devel] [PATCH][uq/master] kvm: x86: Save/restore FPU OP, IP and DP, Avi Kivity, 2011/06/15
- Re: [Qemu-devel] [PATCH][uq/master] kvm: x86: Save/restore FPU OP, IP and DP, Jan Kiszka, 2011/06/15
- Re: [Qemu-devel] [PATCH][uq/master] kvm: x86: Save/restore FPU OP, IP and DP, Jan Kiszka, 2011/06/15
- Re: [Qemu-devel] [PATCH][uq/master] kvm: x86: Save/restore FPU OP, IP and DP, Avi Kivity, 2011/06/15
- Re: [Qemu-devel] [PATCH][uq/master] kvm: x86: Save/restore FPU OP, IP and DP,
Jan Kiszka <=
- Re: [Qemu-devel] [PATCH][uq/master] kvm: x86: Save/restore FPU OP, IP and DP, Avi Kivity, 2011/06/15
- Re: [Qemu-devel] [PATCH][uq/master] kvm: x86: Save/restore FPU OP, IP and DP, Jan Kiszka, 2011/06/15
[Qemu-devel] [PATCH v2][uq/master] kvm: x86: Save/restore FPU OP, IP and DP, Jan Kiszka, 2011/06/15
Re: [Qemu-devel] [PATCH][uq/master] kvm: x86: Save/restore FPU OP, IP and DP, Christophe Fergeau, 2011/06/16