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Re: [PATCH v1 2/4] xen: arm: make VMAP only support in MMU system
- To: Julien Grall <julien@xxxxxxx>, Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>, sstabellini@xxxxxxxxxx, bertrand.marquis@xxxxxxx, michal.orzel@xxxxxxx, Volodymyr_Babchuk@xxxxxxxx
- From: Ayan Kumar Halder <ayankuma@xxxxxxx>
- Date: Mon, 5 Aug 2024 11:44:07 +0100
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- Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx, Penny Zheng <penny.zheng@xxxxxxx>, Wei Chen <wei.chen@xxxxxxx>
- Delivery-date: Mon, 05 Aug 2024 10:44:30 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 02/08/2024 14:27, Julien Grall wrote:
Hi,
Hi Julien,
On 02/08/2024 13:14, Ayan Kumar Halder wrote:
From: Penny Zheng <penny.zheng@xxxxxxx>
VMAP is widely used in ALTERNATIVE feature, CPUERRATA feature, etc to
remap a range of memory with new memory attributes. Since this is
highly dependent on virtual address translation, we choose to fold VMAP
in MMU system.
In this patch, we introduce a new Kconfig CONFIG_HAS_VMAP, and make it
only support in MMU system on ARM architecture. And we make features
like ALTERNATIVE, CPUERRATA, etc, now depend on VMAP.
While I agree that alternative should depend on VMAP (for now), I feel
this is incorrect for CPUERRATA. Very likely, you will need to deal
with them on the MPU.
Before making any suggestion, would you be able to clarify how you
envision to deal with errata? Will they be selected at built time or
boot time?
TBH, I hadn't thought that through. I am thinking about selecting them
at built time (like it is been done for Arm64 cpus).
However given that there are lesser number of MPU cpus (only R52 and
R82) compared to MMU ones, could there be a simpler approach.
I am open to any suggestions you have.
Also, can we disable the CPUERRATA on MPU until we add support for the
first errata ?
- Ayan
Cheers,
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