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Re: [PATCH v3 02/18] xen/arm64: flushtlb: Implement the TLBI repeat workaround for TLB flush by VA


  • To: Julien Grall <julien@xxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • From: Michal Orzel <michal.orzel@xxxxxxx>
  • Date: Tue, 13 Dec 2022 10:23:21 +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 09:23:34 +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>
> 
> Looking at the Neoverse N1 errata document, it is not clear to me
> why the TLBI repeat workaround is not applied for TLB flush by VA.
> 
> The TBL flush by VA helpers are used in flush_xen_tlb_range_va_local()
> and flush_xen_tlb_range_va(). So if the range size if a fixed size smaller
> than a PAGE_SIZE, it would be possible that the compiler remove the loop
> and therefore replicate the sequence described in the erratum 1286807.
> 
> So the TLBI repeat workaround should also be applied for the TLB flush
> by VA helpers.
> 
> Fixes: 22e323d115d8 ("xen/arm: Add workaround for Cortex-A76/Neoverse-N1 
> erratum #1286807")
> Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>

~Michal




 


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