linux-kernel - Re: [PATCH v3 03/11] mm/ioremap: change the return value of io[re|un]map

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Date:   Mon, 10 Oct 2022 08:55:03 +0800
From:   Kefeng Wang <wangkefeng.wang@...wei.com>
To:     Baoquan He <bhe@...hat.com>
CC:     <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        <akpm@...ux-foundation.org>, <hch@...radead.org>,
        <agordeev@...ux.ibm.com>, <christophe.leroy@...roup.eu>,
        <schnelle@...ux.ibm.com>, <David.Laight@...lab.com>,
        <shorne@...il.com>, Arnd Bergmann <arnd@...db.de>,
        <linux-arch@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3 03/11] mm/ioremap: change the return value of
 io[re|un]map_allowed and rename


On 2022/10/10 8:25, Baoquan He wrote:
> On 10/09/22 at 07:13pm, Kefeng Wang wrote:
>> On 2022/10/9 18:31, Baoquan He wrote:
>>> Currently, hooks ioremap_allowed() and iounmap_allowed() are used to
>>> check if it's qualified to do ioremap, and now this is done on ARM64.
>>> However, in oder to convert more architectures to take GENERIC_IOREMAP
>>> method, several more things need be done in those two hooks:
>>>    1) The io address mapping need be handled specifically on architectures,
>>>       e.g arc, ia64, s390;
>>>    2) The original physical address passed into ioremap_prot() need be
>>>       fixed up, e.g arc;
>>>    3) The 'prot' passed into ioremap_prot() need be adjusted, e.g on arc
>>>       and xtensa.
>>>
>>> To handle these three issues,
>>>
>>>    1) Rename ioremap_allowed() and iounmap_allowed() to arch_ioremap()
>>>       and arch_iounmap() since the old name can't reflect their
>>>       functionality after change;
>>>    2) Change the return value of arch_ioremap() so that arch can add
>>>       specifical io address mapping handling inside and return the maped
>>>       address. Now their returned value means:
>>>       ===
>>>       arch_ioremap() return a bool,
>> pointer?
> Right, I forgot fixing it again. Thanks.
>
>>>         - IS_ERR means return an error
>>>         - 0 means continue to remap
>>>         - a non-zero, non-IS_ERR pointer is returned directly
>>>       arch_iounmap() return a bool,
>>>         - true means continue to vunmap
>>>         - false means skip vunmap and return directly
>> ...
>>>    /*
>>> diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
>>> index a68f8fbf423b..2ae16906f3be 100644
>>> --- a/include/asm-generic/io.h
>>> +++ b/include/asm-generic/io.h
>>> @@ -1049,25 +1049,26 @@ static inline void iounmap(volatile void __iomem *addr)
>>>    /*
>>>     * Arch code can implement the following two hooks when using GENERIC_IOREMAP
>>> - * ioremap_allowed() return a bool,
>>> - *   - true means continue to remap
>>> - *   - false means skip remap and return directly
>>> - * iounmap_allowed() return a bool,
>>> + * arch_ioremap() return a bool,
>> ditto...
> Will change.
>
>>>    	area = get_vm_area_caller(size, VM_IOREMAP,
>>>    			__builtin_return_address(0));
>>>    	if (!area)
>>> @@ -52,7 +57,7 @@ void iounmap(volatile void __iomem *addr)
>>>    {
>>>    	void *vaddr = (void *)((unsigned long)addr & PAGE_MASK);
>>> -	if (!iounmap_allowed(vaddr))
>>> +	if (!arch_iounmap((void __iomem *)addr))
>> vaddr?
> No, it's intentional. Alexander suggested this, both of you discussed
> this in v1, see below thread.
ok, please ignore it.
> https://lore.kernel.org/all/Yu4mYxpV0GWRTjQp@li-4a3a4a4c-28e5-11b2-a85c-a8d192c6f089.ibm.com/T/#u
>
>>>    		return;
>>>    	if (is_vmalloc_addr(vaddr))
>
> .