Re: [Xen-devel] [PATCH v2 0/3] x86emul: VME/PVI mode fixes

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 06.11.18 at 15:21, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 06/11/18 13:33, Jan Beulich wrote:
>> 1: skip VIF processing in VME mode for 16-bit POPF at IOPL 3
>> 2: raise #GP(0) in VME mode for POPF with TF set in new value
> 
> I'm afraid that I think there is still a bug with PVI emulation.
> 
> We only ever read cr4 when operating in vm86, which means that the later
> logic checking VME doesn't apply to 16bit protected mode execution.

And where on the instruction page in the SDM do you see CR4.PVI
mattering for POPF? Quite the opposite - there is:

"(The protected-mode virtual-interrupt feature — enabled by
 setting CR4.PVI — affects the CLI and STI instructions in the
 same manner as the virtual-8086 mode extensions. POPF,
 however, is not affected by CR4.PVI.)"

Even if there was a further issue, it would be orthogonal to the
changes here, i.e. you'd only make me add yet another patch.
IOW I don't think the comment affects the patches currently in
this series.

Jan


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