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Re: [PATCH v3 4/9] xen/riscv: setup fixmap mapping
- To: oleksii.kurochko@xxxxxxxxx
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 5 Aug 2024 17:45:37 +0200
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- Cc: Alistair Francis <alistair.francis@xxxxxxx>, Bob Eshleman <bobbyeshleman@xxxxxxxxx>, Connor Davis <connojdavis@xxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>
- Delivery-date: Mon, 05 Aug 2024 15:45:42 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 05.08.2024 17:13, oleksii.kurochko@xxxxxxxxx wrote:
> On Mon, 2024-07-29 at 15:35 +0200, Jan Beulich wrote:
>>> + }
>>> +
>>> + BUG_ON(pte_is_valid(*pte));
>>> +
>>> + tmp = paddr_to_pte(LINK_TO_LOAD((unsigned long)&xen_fixmap),
>>> PTE_TABLE);
>>
>> I'm a little puzzled by the use of LINK_TO_LOAD() (and LOAD_TO_LINK()
>> a
>> little further up) here. Don't you have functioning __pa() and
>> __va()?
> Can __pa() and __va() be used in this case?
>
> According to comments for other architectures, these macros are used
> for converting between Xen heap virtual addresses (VA) and machine
> addresses (MA). I may have misunderstood what is meant by the Xen heap
> in this context, but I'm not sure if xen_fixmap[] and page tables are
> considered part of the Xen heap.
I didn't check Arm, but on x86 virt_to_maddr() (underlying __pa()) has
special case code to also allow addresses within the Xen image (area).
Jan
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