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RE: [PATCH v4 03/14] xen/arm32: flushtlb: Reduce scope of barrier for local TLB flush
- To: Julien Grall <julien@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Henry Wang <Henry.Wang@xxxxxxx>
- Date: Fri, 13 Jan 2023 13:46:31 +0000
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- Cc: Luca Fancellu <Luca.Fancellu@xxxxxxx>, Julien Grall <jgrall@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Bertrand Marquis <Bertrand.Marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>
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- Thread-topic: [PATCH v4 03/14] xen/arm32: flushtlb: Reduce scope of barrier for local TLB flush
Hi Julien,
> -----Original Message-----
> Subject: [PATCH v4 03/14] xen/arm32: flushtlb: Reduce scope of barrier for
> local TLB flush
>
> 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>
I've tested this patch on FVP in arm32 execution mode using the same
testing approach for patch#1, and this patch is good, so:
Tested-by: Henry Wang <Henry.Wang@xxxxxxx>
Kind regards,
Henry
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