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Re: [PATCH v3 03/18] xen/arm32: flushtlb: Reduce scope of barrier for local TLB flush
- To: Julien Grall <julien@xxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Michal Orzel <michal.orzel@xxxxxxx>
- Date: Tue, 13 Dec 2022 11:48:57 +0100
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- Cc: <Luca.Fancellu@xxxxxxx>, Julien Grall <jgrall@xxxxxxxxxx>, "Stefano Stabellini" <sstabellini@xxxxxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
- Delivery-date: Tue, 13 Dec 2022 10:49:15 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
Hi Julien,
On 12/12/2022 10:55, Julien Grall wrote:
>
>
> From: Julien Grall <jgrall@xxxxxxxxxx>
>
> Per G5-9224 in ARM DDI 0487I.a:
>
> "A DSB NSH is sufficient to ensure completion of TLB maintenance
> instructions that apply to a single PE. A DSB ISH is sufficient to
> ensure completion of TLB maintenance instructions that apply to PEs
> in the same Inner Shareable domain.
> "
>
> This is quoting the Armv8 specification because I couldn't find an
> explicit statement in the Armv7 specification. Instead, I could find
> bits in various places that confirm the same implementation.
>
> Furthermore, Linux has been using 'nsh' since 2013 (62cbbc42e001
> "ARM: tlb: reduce scope of barrier domains for TLB invalidation").
>
> This means barrier after local TLB flushes could be reduced to
> non-shareable.
>
> Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>
~Michal
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