linux-kernel - Re: [PATCH v2] x86: pat: Do not compile stubbed functions when X86

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Date:   Sun, 11 Apr 2021 11:12:32 +0200
From:   Jan Kiszka <jan.kiszka@....de>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86 <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] x86: pat: Do not compile stubbed functions when
 X86_PAT is off

On 11.04.21 11:10, Borislav Petkov wrote:
> On Sun, Apr 11, 2021 at 10:22:19AM +0200, Jan Kiszka wrote:
>> On 26.10.20 18:39, Jan Kiszka wrote:
>>> From: Jan Kiszka <jan.kiszka@...mens.com>
>>>
>>> Those are already provided by linux/io.h as stubs.
>>>
>>> The conflict remains invisible until someone would pull linux/io.h into
>>> memtype.c.
>>>
>>> Signed-off-by: Jan Kiszka <jan.kiszka@...mens.com>
>>> ---
>>>
>>> Change in v2:
>>>  - correct commit message
>>>
>>>  arch/x86/mm/pat/memtype.c | 2 ++
>>>  1 file changed, 2 insertions(+)
>>>
>>> diff --git a/arch/x86/mm/pat/memtype.c b/arch/x86/mm/pat/memtype.c
>>> index 8f665c352bf0..41a4ac585af3 100644
>>> --- a/arch/x86/mm/pat/memtype.c
>>> +++ b/arch/x86/mm/pat/memtype.c
>>> @@ -800,6 +800,7 @@ void memtype_free_io(resource_size_t start, resource_size_t end)
>>>  	memtype_free(start, end);
>>>  }
>>>
>>> +#ifdef CONFIG_X86_PAT
>>>  int arch_io_reserve_memtype_wc(resource_size_t start, resource_size_t size)
>>>  {
>>>  	enum page_cache_mode type = _PAGE_CACHE_MODE_WC;
>>> @@ -813,6 +814,7 @@ void arch_io_free_memtype_wc(resource_size_t start, resource_size_t size)
>>>  	memtype_free_io(start, start + size);
>>>  }
>>>  EXPORT_SYMBOL(arch_io_free_memtype_wc);
>>> +#endif
>>>
>>>  pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
>>>  				unsigned long size, pgprot_t vma_prot)
>>>
>>
>> What happened to this?
>
> What is this patch and your other asm/proto.h thing fixing?
>
> Looks like you're using kernel headers in something else and don't want
> to include the whole world thus those fixes... so that you can include
> upstream kernel headers without having to touch them...
>
> Or am I way off base here?
>

The patches are coming from downstream usage, yes, but I think the
solutions are relevant cleanups for upstream as well.

Jan