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Re: [PATCH v7 8/8] xen/arm: mmu: move MMU specific P2M code to mmu/p2m.{c,h}
- To: Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Bertrand Marquis <Bertrand.Marquis@xxxxxxx>
- From: Henry Wang <Henry.Wang@xxxxxxx>
- Date: Sat, 14 Oct 2023 01:30:21 +0000
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- Cc: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Penny Zheng <Penny.Zheng@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Wei Chen <Wei.Chen@xxxxxxx>
- Delivery-date: Sat, 14 Oct 2023 01:30:44 +0000
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- Thread-topic: [PATCH v7 8/8] xen/arm: mmu: move MMU specific P2M code to mmu/p2m.{c,h}
Hi Julien,
(Sending this email directly “To:” Bertrand and Stefano to catch their
attention about
one question that you ask them)
> On Oct 14, 2023, at 02:31, Julien Grall <julien@xxxxxxx> wrote:
>
> Hi Henry,
>
> some more remarks.
>
> On 09/10/2023 02:03, Henry Wang wrote:
>> +/*
>> + * Invalidate all entries in the root page-tables. This is
>> + * useful to get fault on entry and do an action.
>> + *
>> + * p2m_invalid_root() should not be called when the P2M is shared with
>> + * the IOMMU because it will cause IOMMU fault.
>> + */
>> +void p2m_invalidate_root(struct p2m_domain *p2m)
>
> I think this function doesn't make sense for the MPU. What would invalidate?
>
> The only caller outside of the file is in arch_domain_creation_finished().
> This was used for set/way emulation which I believe will be difficult to
> implement efficiently for the MPU (see my other reply to this patch).
>
> So I would consider to move arch_domain_creation_finished() in mmu/p2m.c or
> creating a new function p2m_domain_creation_finished() which is called from
> arch_domain_creation_finished().
Yeah make sense, I will do the suggested change in v8.
> [...]
>
>> +/*
>> + * Clean & invalidate RAM associated to the guest vCPU.
>> + *
>> + * The function can only work with the current vCPU and should be called
>> + * with IRQ enabled as the vCPU could get preempted.
>> + */
>> +void p2m_flush_vm(struct vcpu *v)
> I believe an implementation of p2m_flush_vm() would be quite expensive for
> the MPU. It would be better to not emulate set/way for now.
>
> It would also feel a bit odd to leave it unimplemented and called from
> check_for_vcpu_work(). So maybe we want to rename it. I don't have a goood
> name suggestion though. Bertrand, Stefano?
See the beginning of this email.
Kind regards,
Henry
>
> [...]
>
> --
> Julien Grall
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