linux-kernel - Re: 回复: [PATCH 2/2] uio:powerpc:mpc85xx: l2-cache-sram uio driver implementation

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Message-ID: <c76598b5-2d60-ea22-d590-4cc6998a8830@csgroup.eu>
Date:   Tue, 14 Jun 2022 09:26:04 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Wenhu Wang <wenhu.wang@...mail.com>,
        Greg KH <gregkh@...uxfoundation.org>
Cc:     "mpe@...erman.id.au" <mpe@...erman.id.au>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: 回复: [PATCH 2/2] uio:powerpc:mpc85xx: l2-cache-sram uio driver implementation



Le 14/06/2022 à 09:18, Christophe Leroy a écrit :
> 
> 
> Le 14/06/2022 à 08:09, Wenhu Wang a écrit :
>>>> +static const struct vm_operations_struct uio_cache_sram_vm_ops = {
>>>> +#ifdef CONFIG_HAVE_IOREMAP_PROT
>>>
>>> Same here.
>>>
>>
>> I tried to eliminate it in mainline
>> See: [PATCH v2] mm: eliminate ifdef of HAVE_IOREMAP_PROT in .c files
>> https://lkml.org/lkml/2022/6/10/695
>>
> 
> I looked at that patch.
> 
> I don't think you can just drop the #ifdef in function 
> __access_remote_vm() in mm/memory.c
> 
> You have to replace it with something like:
> 
>      if (!IS_ENABLED(CONFIG_HAVE_IOREMAP_PROT))
>          break;
> 


Another thing in that patch:

By making generic_access_phys() a static inline, it means that everytime 
you refer to the address of that function in a vm_operations_struct 
struct, the compiler has to provide an outlined instance of the 
function. It means you'll likely have several instances of a 
generic_access_phys().

What you could do instead is to add the following at the start of 
generic_access_phys() in mm/memory.c :

	if (!IS_ENABLED(CONFIG_HAVE_IOREMAP_PROT))
		return 0;