Re: [Xen-devel] [PATCH 3/4] x86emul: correct handling of FPU insns faulting on memory write

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: Monday, March 13, 2017 7:05 PM
> 
> When an FPU instruction with a memory destination fails during the memory
> write, it should not affect FPU register state. Due to the way we emulate FPU
> (and SIMD) instructions, we can only guarantee this by
> - backing out changes to the FPU register state in such a case or
> - doing a descriptor read and/or page walk up front, perhaps with the
>   stubs accessing the actual memory location then.
> The latter would require a significant change in how the emulator does its
> guest memory accessing, so for now the former variant is being chosen.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>

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