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Subject: Re: [PATCH v12 04/10] set_memory: allow querying whether
 set_direct_map_*() is actually enabled
To:     Mike Rapoport <rppt@linux.ibm.com>
Cc:     Mike Rapoport <rppt@kernel.org>,
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 <20201125092208.12544-5-rppt@kernel.org>
 <5ea6eacd-79e8-0645-da39-d3461f60e627@redhat.com>
 <20201125121138.GJ123287@linux.ibm.com>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat GmbH
Message-ID: <bb27ab9e-8c74-e297-acc1-a92bcc4087a9@redhat.com>
Date:   Wed, 25 Nov 2020 13:42:36 +0100
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On 25.11.20 13:11, Mike Rapoport wrote:
> On Wed, Nov 25, 2020 at 12:22:52PM +0100, David Hildenbrand wrote:
>>>  #include <asm-generic/cacheflush.h>
>>>  
>>>  #endif /* __ASM_CACHEFLUSH_H */
>>> diff --git a/arch/arm64/include/asm/set_memory.h b/arch/arm64/include/asm/set_memory.h
>>> new file mode 100644
>>> index 000000000000..ecb6b0f449ab
>>> --- /dev/null
>>> +++ b/arch/arm64/include/asm/set_memory.h
>>> @@ -0,0 +1,17 @@
>>> +/* SPDX-License-Identifier: GPL-2.0-only */
>>> +
>>> +#ifndef _ASM_ARM64_SET_MEMORY_H
>>> +#define _ASM_ARM64_SET_MEMORY_H
>>> +
>>> +#include <asm-generic/set_memory.h>
>>> +
>>> +bool can_set_direct_map(void);
>>> +#define can_set_direct_map can_set_direct_map
>>
>> Well, that looks weird.
>> [...]
> 
> We have a lot of those e.g. in linux/pgtable.h
> 
>>>  }
>>> +#else /* CONFIG_ARCH_HAS_SET_DIRECT_MAP */
>>> +/*
>>> + * Some architectures, e.g. ARM64 can disable direct map modifications at
>>> + * boot time. Let them overrive this query.
>>> + */
>>> +#ifndef can_set_direct_map
>>> +static inline bool can_set_direct_map(void)
>>> +{
>>> +	return true;
>>> +}
>>
>> I think we prefer __weak functions for something like that, avoids the
>> ifdefery.
> 
> I'd prefer this for two reasons: first, static inline can be optimized
> away and second, there is no really good place to put generic
> implementation.

Fair enough

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Thanks,

David / dhildenb