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

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

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.

I can't find a useful description of the order of events in a task
switch in either manual.

~Andrew

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