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Date:   Mon, 6 Jun 2022 23:14:18 +0800
From:   Baoquan He <bhe@redhat.com>
To:     Kefeng Wang <wangkefeng.wang@huawei.com>
Cc:     catalin.marinas@arm.com, will@kernel.org,
        akpm@linux-foundation.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        hch@infradead.org, arnd@arndb.de, anshuman.khandual@arm.com
Subject: Re: [PATCH v4 4/6] mm: ioremap: Add ioremap/iounmap_allowed()
Message-ID: <Yp4Zyt/WJjy3Mj4Y@MiWiFi-R3L-srv>
References: <20220606074815.139265-1-wangkefeng.wang@huawei.com>
 <20220606074815.139265-5-wangkefeng.wang@huawei.com>
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On 06/06/22 at 03:48pm, Kefeng Wang wrote:
> Add special hook for architecture to verify addr, size or prot
> when ioremap() or iounmap(), which will make the generic ioremap
> more useful.
> 
>   ioremap_allowed() return an int,
>     - NULL means continue to remap
>     - error code means skip remap and return directly
>   iounmap_allowed() return an int,
>     - 0 means continue to vunmap
>     - error code means skip vunmap and return directly

Aren't they bool type function and better return bool value?

> 
> Acked-by: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> ---
>  include/asm-generic/io.h | 25 +++++++++++++++++++++++++
>  mm/ioremap.c             | 13 ++++++++++---
>  2 files changed, 35 insertions(+), 3 deletions(-)
> 
> diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
> index e6ffa2519f08..9429387a3e65 100644
> --- a/include/asm-generic/io.h
> +++ b/include/asm-generic/io.h
> @@ -964,6 +964,31 @@ static inline void iounmap(volatile void __iomem *addr)
>  #elif defined(CONFIG_GENERIC_IOREMAP)
>  #include <linux/pgtable.h>
>  
> +/*
> + * Arch code can implement the following two special hooks when using GENERIC_IOREMAP
> + * ioremap_allowed() return an int,
> + *   - 0 means continue to remap
> + *   - error code means skip remap and return directly
> + * iounmap_allowed() return an int,
> + *   - 0 means continue to vunmap
> + *   - error code means skip vunmap and return directly
> + */
> +#ifndef ioremap_allowed
> +#define ioremap_allowed ioremap_allowed
> +static inline int ioremap_allowed(phys_addr_t phys_addr, size_t size, unsigned long prot)
> +{
> +	return 0;
> +}
> +#endif
> +
> +#ifndef iounmap_allowed
> +#define iounmap_allowed iounmap_allowed
> +static inline int iounmap_allowed(void __iomem *addr)
> +{
> +	return 0;
> +}
> +#endif
> +
>  void __iomem *ioremap_prot(phys_addr_t phys_addr, size_t size, unsigned long prot);
>  void iounmap(volatile void __iomem *addr);
>  
> diff --git a/mm/ioremap.c b/mm/ioremap.c
> index 7cb9996b0c12..196c93c0beb8 100644
> --- a/mm/ioremap.c
> +++ b/mm/ioremap.c
> @@ -27,8 +27,10 @@ void __iomem *ioremap_prot(phys_addr_t phys_addr, size_t size, unsigned long pro
>  	phys_addr -= offset;
>  	size = PAGE_ALIGN(size + offset);
>  
> -	area = get_vm_area_caller(size, VM_IOREMAP,
> -			__builtin_return_address(0));
> +	if (ioremap_allowed(phys_addr, size, prot))
> +		return NULL;
> +
> +	area = get_vm_area_caller(size, VM_IOREMAP, __builtin_return_address(0));
>  	if (!area)
>  		return NULL;
>  	vaddr = (unsigned long)area->addr;
> @@ -45,6 +47,11 @@ EXPORT_SYMBOL(ioremap_prot);
>  
>  void iounmap(volatile void __iomem *addr)
>  {
> -	vunmap((void *)((unsigned long)addr & PAGE_MASK));
> +	void __iomem *vaddr = (void __iomem *)((unsigned long)addr & PAGE_MASK);
> +
> +	if (iounmap_allowed(vaddr))
> +		return;
> +
> +	vunmap((void __force *)vaddr);
>  }
>  EXPORT_SYMBOL(iounmap);
> -- 
> 2.35.3
> 
>