Re: [Xen-devel] [PATCH 1/3] x86/HVM: limit writes to incoming TSS during task switch

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 23/11/16 08:27, Jan Beulich wrote:
>>>> On 22.11.16 at 17:32, <andrew.cooper3@xxxxxxxxxx> wrote:
>> On 22/11/16 13:55, Jan Beulich wrote:
>>> The only field modified (and even that conditionally) is the back link.
>>> Write only that field, and only when it actually has been written to.
>>>
>>> Take the opportunity and also ditch the pointless initializer from the
>>> "tss" local variable.
>> It would help to point out that tss is unconditionally filled completely
>> from guest memory.
>>
>>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>> As for the mechanical adjustments here, Reviewed-by: Andrew Cooper
>> <andrew.cooper3@xxxxxxxxxx>
>>
>> However, is the position of the backlink write actually correct?  I'd
>> have thought that all access to the old tss happen before switching cr3.
> But the backlink gets written into the incoming TSS.

Ah - of course it does.  I was getting confused by the repeated use of
the tss structure.  Sorry for the noise.

~Andrew

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