linux-kernel - Re: [PATCH v3 05/11] arc: mm: Convert to GENERIC

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Date:   Wed, 12 Oct 2022 10:17:13 +0000
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Baoquan He <bhe@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "hch@...radead.org" <hch@...radead.org>,
        "agordeev@...ux.ibm.com" <agordeev@...ux.ibm.com>,
        "wangkefeng.wang@...wei.com" <wangkefeng.wang@...wei.com>,
        "schnelle@...ux.ibm.com" <schnelle@...ux.ibm.com>,
        "David.Laight@...LAB.COM" <David.Laight@...LAB.COM>,
        "shorne@...il.com" <shorne@...il.com>,
        Vineet Gupta <vgupta@...nel.org>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>
Subject: Re: [PATCH v3 05/11] arc: mm: Convert to GENERIC_IOREMAP



Le 09/10/2022 à 12:31, Baoquan He a écrit :
> By taking GENERIC_IOREMAP method, the generic ioremap_prot() and
> iounmap() are visible and available to arch. Arch only needs to
> provide implementation of arch_ioremap() or arch_iounmap() if there's
> arch specific handling needed in its ioremap() or iounmap(). This
> change will simplify implementation by removing duplicated codes with
> generic ioremap() and iounmap(), and has the equivalent functioality
> as before.
> 
> Here, add hooks arch_ioremap() and arch_iounmap() for arc's special
> operation when ioremap_prot() and iounmap(). Meanwhile define and
> implement arc's own ioremap() because arc has some special handling
> in ioremap() than standard ioremap().
> 
> Signed-off-by: Baoquan He <bhe@...hat.com>
> Cc: Vineet Gupta <vgupta@...nel.org>
> Cc: linux-snps-arc@...ts.infradead.org
> ---
>   arch/arc/Kconfig          |  1 +
>   arch/arc/include/asm/io.h | 19 +++++++++----
>   arch/arc/mm/ioremap.c     | 60 ++++++---------------------------------
>   3 files changed, 23 insertions(+), 57 deletions(-)
> 
> diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
> index 9e3653253ef2..a08d2abfaf61 100644
> --- a/arch/arc/Kconfig
> +++ b/arch/arc/Kconfig
> @@ -26,6 +26,7 @@ config ARC
>   	select GENERIC_PENDING_IRQ if SMP
>   	select GENERIC_SCHED_CLOCK
>   	select GENERIC_SMP_IDLE_THREAD
> +	select GENERIC_IOREMAP
>   	select HAVE_ARCH_KGDB
>   	select HAVE_ARCH_TRACEHOOK
>   	select HAVE_ARCH_TRANSPARENT_HUGEPAGE if ARC_MMU_V4
> diff --git a/arch/arc/include/asm/io.h b/arch/arc/include/asm/io.h
> index 8f777d6441a5..41a317567920 100644
> --- a/arch/arc/include/asm/io.h
> +++ b/arch/arc/include/asm/io.h
> @@ -20,9 +20,20 @@
>   #define __iowmb()		do { } while (0)
>   #endif
>   
> -extern void __iomem *ioremap(phys_addr_t paddr, unsigned long size);
> -extern void __iomem *ioremap_prot(phys_addr_t paddr, unsigned long size,
> -				  unsigned long flags);
> +/*
> + * I/O memory mapping functions.
> + */
> +
> +void __iomem *
> +arch_ioremap(phys_addr_t *paddr, size_t size, unsigned long *prot_val);
> +#define arch_ioremap arch_ioremap
> +
> +bool arch_iounmap(void __iomem *addr);
> +#define arch_iounmap arch_iounmap
> +
> +void __iomem *ioremap(phys_addr_t paddr, unsigned long size);
> +#define ioremap ioremap
> +
>   static inline void __iomem *ioport_map(unsigned long port, unsigned int nr)
>   {
>   	return (void __iomem *)port;
> @@ -32,8 +43,6 @@ static inline void ioport_unmap(void __iomem *addr)
>   {
>   }
>   
> -extern void iounmap(const void __iomem *addr);
> -
>   /*
>    * io{read,write}{16,32}be() macros
>    */
> diff --git a/arch/arc/mm/ioremap.c b/arch/arc/mm/ioremap.c
> index 0ee75aca6e10..c2dcacd56aca 100644
> --- a/arch/arc/mm/ioremap.c
> +++ b/arch/arc/mm/ioremap.c
> @@ -25,13 +25,6 @@ static inline bool arc_uncached_addr_space(phys_addr_t paddr)
>   
>   void __iomem *ioremap(phys_addr_t paddr, unsigned long size)
>   {
> -	phys_addr_t end;
> -
> -	/* Don't allow wraparound or zero size */
> -	end = paddr + size - 1;
> -	if (!size || (end < paddr))
> -		return NULL;
> -
>   	/*
>   	 * If the region is h/w uncached, MMU mapping can be elided as optim
>   	 * The cast to u32 is fine as this region can only be inside 4GB
> @@ -44,62 +37,25 @@ void __iomem *ioremap(phys_addr_t paddr, unsigned long size)
>   }
>   EXPORT_SYMBOL(ioremap);
>   
> -/*
> - * ioremap with access flags
> - * Cache semantics wise it is same as ioremap - "forced" uncached.
> - * However unlike vanilla ioremap which bypasses ARC MMU for addresses in
> - * ARC hardware uncached region, this one still goes thru the MMU as caller
> - * might need finer access control (R/W/X)
> - */
> -void __iomem *ioremap_prot(phys_addr_t paddr, unsigned long size,
> -			   unsigned long flags)
> +void __iomem *
> +arch_ioremap(phys_addr_t *paddr, size_t size, unsigned long *prot_val)
>   {
> -	unsigned int off;
> -	unsigned long vaddr;
> -	struct vm_struct *area;
> -	phys_addr_t end;
> -	pgprot_t prot = __pgprot(flags);
> -
> -	/* Don't allow wraparound, zero size */
> -	end = paddr + size - 1;
> -	if ((!size) || (end < paddr))
> -		return NULL;
> -
>   	/* An early platform driver might end up here */
>   	if (!slab_is_available())
> -		return NULL;
> +		return IOMEM_ERR_PTR(-EINVAL);

I think the slab_is_available() check should be done in the generic 
functions. On all architectures SLAB must be available before you can 
use get_vm_area_caller() and vunmap()

Christophe