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RE: [PATCH v2 03/40] xen/arm: adjust Xen TLB helpers for Armv8-R64 PMSA
- To: Julien Grall <julien@xxxxxxx>, Penny Zheng <Penny.Zheng@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Wei Chen <Wei.Chen@xxxxxxx>
- Date: Wed, 18 Jan 2023 02:32:52 +0000
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- Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Bertrand Marquis <Bertrand.Marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
- Delivery-date: Wed, 18 Jan 2023 02:33:18 +0000
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- Thread-topic: [PATCH v2 03/40] xen/arm: adjust Xen TLB helpers for Armv8-R64 PMSA
Hi Julien,
> -----Original Message-----
> From: Julien Grall <julien@xxxxxxx>
> Sent: 2023年1月18日 7:17
> To: Penny Zheng <Penny.Zheng@xxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxxx
> Cc: Wei Chen <Wei.Chen@xxxxxxx>; Stefano Stabellini
> <sstabellini@xxxxxxxxxx>; Bertrand Marquis <Bertrand.Marquis@xxxxxxx>;
> Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
> Subject: Re: [PATCH v2 03/40] xen/arm: adjust Xen TLB helpers for Armv8-
> R64 PMSA
>
> Hi,
>
> On 13/01/2023 05:28, Penny Zheng wrote:
> > From: Wei Chen <wei.chen@xxxxxxx>
> >
> > From Arm ARM Supplement of Armv8-R AArch64 (DDI 0600A) [1],
> > section D1.6.2 TLB maintenance instructions, we know that
> > Armv8-R AArch64 permits an implementation to cache stage 1
> > VMSAv8-64 and stage 2 PMSAv8-64 attributes as a common entry
> > for the Secure EL1&0 translation regime. But for Xen itself,
> > it's running with stage 1 PMSAv8-64 on Armv8-R AArch64. The
> > EL2 MPU updates for stage 1 PMSAv8-64 will not be cached in
> > TLB entries. So we don't need any TLB invalidation for Xen
> > itself in EL2.
>
> So I understand the theory here. But I would expect that none of the
> common code will call any of those helpers. Therefore the #ifdef should
> be unnecessary.
>
> Can you clarify if my understanding is correct?
>
Yes, you're right, after we separate common code and MMU code, these
helpers will be called in MMU specific code only. We will drop this
patch in next version.
Cheers,
Wei Chen
> Cheers,
>
> --
> Julien Grall
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