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Re: [PATCH] move __read_mostly to xen/cache.h
- To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 8 Aug 2023 12:35:13 +0200
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- Cc: George Dunlap <george.dunlap@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>, Shawn Anastasio <sanastasio@xxxxxxxxxxxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Tue, 08 Aug 2023 10:35:22 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 08.08.2023 12:32, Jan Beulich wrote:
> On 08.08.2023 12:18, Andrew Cooper wrote:
>> On 08/08/2023 10:46 am, Jan Beulich wrote:
>>> There's no need for every arch to define its own identical copy. If down
>>> the road an arch needs to customize it, we can add #ifndef around the
>>> common #define.
>>>
>>> To be on the safe side build-breakage-wise, change a couple of #include
>>> <asm/cache.h> to the xen/ equivalent.
>>>
>>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>>
>> Could we find a better place to put this?
>>
>> __read_mostly is just a section. It's relationship to the cache is only
>> microarchitectural, and is not the same kind of information as the rest
>> of cache.h
>>
>> __ro_after_init is only here because __read_mostly is here, but has
>> absolutely nothing to do with caches whatsoever.
>>
>> If we're cleaning them up, they ought to live elsewhere.
>
> I would be considering init.h (for having most other __section() uses,
> and for also needing __read_mostly), but that's not a great place to
> put these either. In fact I see less connection there than for cache.h.
> So the primary need is a good suggestion (I'm hesitant to suggest to
> introduce section.h just for this). In the absence of this, can we
> perhaps deal with this in a 2nd step, thus not blocking this patch and
> therefore not needing to then also clean up PPC-specific code?
Oh, also: I we move them elsewhere, it wouldn't be logical for xen/cache.h
to include that other header as well. Yet without that the risk of build
breakages (perhaps in only exotic configs) is of course quite a bit higher.
Jan
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