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From: | Avi Kivity |
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 |
User-agent: | Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110428 Fedora/3.1.10-1.fc15 Lightning/1.0b3pre Thunderbird/3.1.10 |
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
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