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Re: [PATCH 2/2] x86/fpu: Initialise FTW as well as FCW in xstate_alloc_save_area()
- To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Fri, 27 Mar 2026 11:07:04 +0100
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- Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Fri, 27 Mar 2026 10:07:09 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 26.03.2026 20:04, Andrew Cooper wrote:
> xstate_alloc_save_area() configures FCW and MXCSR to #RESET values but misses
> FTW. Fixing this means that the backing memory always has an architecturally
> correct value.
>
> Adjust the comment to state that it's the #RESET values which we care about.
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
The title using "as well as" reads to me as if both are being fixed, when
really you bring FTW in line with FCW. Preferably with this adjusted to be
unambiguous:
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
> I don't understand what the rest of the comment is trying to say, so have left
> it alone. There's still a lot of cleanup to be done to merge i387 and xstate.
I think it tries to say that the values put in memory aren't actually going
to be used by a subsequent XRSTOR, by it putting the respective registers
into init-state without reading memory.
Jan
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