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Re: [PATCH for-4.21 1/2] x86/AMD: avoid REP MOVSB for Zen3/4
- To: Teddy Astie <teddy.astie@xxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Jason Andryuk <jason.andryuk@xxxxxxx>
- Date: Mon, 29 Sep 2025 19:35:53 -0400
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
- Delivery-date: Mon, 29 Sep 2025 23:36:18 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 2025-09-25 08:18, Teddy Astie wrote:
Le 25/09/2025 à 12:48, Jan Beulich a écrit :
Along with Zen2 (which doesn't expose ERMS), both families reportedly
suffer from sub-optimal aliasing detection when deciding whether REP MOVSB
can actually be carried out the accelerated way. Therefore we want to
avoid its use in the common case (memset(), copy_page_hot()).
s/memset/memcpy (memset probably uses rep stosb which is not affected IIUC)
Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
With Teddy's suggested change:
Reviewed-by: Jason Andryuk <jason.andryuk@xxxxxxx>
Thanks,
Jason
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