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Re: [PATCH v3 7/7] mm: allow page scrubbing routine(s) to be arch controlled
- To: Julien Grall <julien@xxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 26 Nov 2024 09:02:48 +0100
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- Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Bobby Eshleman <bobbyeshleman@xxxxxxxxx>, Alistair Francis <alistair.francis@xxxxxxx>, Connor Davis <connojdavis@xxxxxxxxx>, Shawn Anastasio <sanastasio@xxxxxxxxxxxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Tue, 26 Nov 2024 08:03:01 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 25.11.2024 23:17, Julien Grall wrote:
>> --- a/xen/arch/arm/include/asm/page.h
>> +++ b/xen/arch/arm/include/asm/page.h
>> @@ -144,6 +144,12 @@ extern size_t dcache_line_bytes;
>>
>> #define copy_page(dp, sp) memcpy(dp, sp, PAGE_SIZE)
>>
>> +#define clear_page_hot clear_page
>> +#define clear_page_cold clear_page
>> +
>> +#define scrub_page_hot(page) memset(page, SCRUB_BYTE_PATTERN, PAGE_SIZE)
>> +#define scrub_page_cold scrub_page_hot
>
> This block seems to be common between all the arch but x86. Should we
> add an header in asm generic?
I'd say that largely depends on the intentions of Arm, RISC-V, and PPC.
Personally I've always found it odd that memset() / memcpy() are used for
page clearing / copying. Surely there are better ways, and pretty certainly
about every arch also has distinct means to efficiently do "hot" and "cold"
clearing. Therefore keeping these #define-s in per-arch headers imo serves
as a reminder that something wants doing about them.
Jan
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