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

From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Wenhu Wang <wenhu.wang@hotmail.com>,
	Greg KH <gregkh@linuxfoundation.org>
Cc: "mpe@ellerman.id.au" <mpe@ellerman.id.au>,
	"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: 回复: [PATCH 2/2] uio:powerpc:mpc85xx: l2-cache-sram uio driver implementation
Date: Tue, 14 Jun 2022 09:26:04 +0200	[thread overview]
Message-ID: <c76598b5-2d60-ea22-d590-4cc6998a8830@csgroup.eu> (raw)
In-Reply-To: <efebcb50-0481-622a-894c-7000999aacc6@csgroup.eu>

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;