linux-kernel - Re: [Patch V6 12/16] mm: provide early_memremap

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Date:	Tue, 21 Jul 2015 06:49:04 +0200
From:	Juergen Gross <jgross@...e.com>
To:	linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
	linux-mm@...ck.org, linux-arch@...r.kernel.org
Cc:	xen-devel@...ts.xensource.com, konrad.wilk@...cle.com,
	david.vrabel@...rix.com, boris.ostrovsky@...cle.com
Subject: Re: [Patch V6 12/16] mm: provide early_memremap_ro to establish
 read-only mapping

Hi MM maintainers,

this patch is the last requiring an ack for the series to go in.
Could you please comment?


Juergen

On 07/17/2015 06:51 AM, Juergen Gross wrote:
> During early boot as Xen pv domain the kernel needs to map some page
> tables supplied by the hypervisor read only. This is needed to be
> able to relocate some data structures conflicting with the physical
> memory map especially on systems with huge RAM (above 512GB).
>
> Provide the function early_memremap_ro() to provide this read only
> mapping.
>
> Signed-off-by: Juergen Gross <jgross@...e.com>
> Acked-by: Konrad Rzeszutek Wilk <Konrad.wilk@...cle.com>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: linux-mm@...ck.org
> Cc: linux-arch@...r.kernel.org
> ---
>   include/asm-generic/early_ioremap.h |  2 ++
>   include/asm-generic/fixmap.h        |  3 +++
>   mm/early_ioremap.c                  | 12 ++++++++++++
>   3 files changed, 17 insertions(+)
>
> diff --git a/include/asm-generic/early_ioremap.h b/include/asm-generic/early_ioremap.h
> index a5de55c..316bd04 100644
> --- a/include/asm-generic/early_ioremap.h
> +++ b/include/asm-generic/early_ioremap.h
> @@ -11,6 +11,8 @@ extern void __iomem *early_ioremap(resource_size_t phys_addr,
>   				   unsigned long size);
>   extern void *early_memremap(resource_size_t phys_addr,
>   			    unsigned long size);
> +extern void *early_memremap_ro(resource_size_t phys_addr,
> +			       unsigned long size);
>   extern void early_iounmap(void __iomem *addr, unsigned long size);
>   extern void early_memunmap(void *addr, unsigned long size);
>
> diff --git a/include/asm-generic/fixmap.h b/include/asm-generic/fixmap.h
> index f23174f..1cbb833 100644
> --- a/include/asm-generic/fixmap.h
> +++ b/include/asm-generic/fixmap.h
> @@ -46,6 +46,9 @@ static inline unsigned long virt_to_fix(const unsigned long vaddr)
>   #ifndef FIXMAP_PAGE_NORMAL
>   #define FIXMAP_PAGE_NORMAL PAGE_KERNEL
>   #endif
> +#if !defined(FIXMAP_PAGE_RO) && defined(PAGE_KERNEL_RO)
> +#define FIXMAP_PAGE_RO PAGE_KERNEL_RO
> +#endif
>   #ifndef FIXMAP_PAGE_NOCACHE
>   #define FIXMAP_PAGE_NOCACHE PAGE_KERNEL_NOCACHE
>   #endif
> diff --git a/mm/early_ioremap.c b/mm/early_ioremap.c
> index e10ccd2..0cfadaf 100644
> --- a/mm/early_ioremap.c
> +++ b/mm/early_ioremap.c
> @@ -217,6 +217,13 @@ early_memremap(resource_size_t phys_addr, unsigned long size)
>   	return (__force void *)__early_ioremap(phys_addr, size,
>   					       FIXMAP_PAGE_NORMAL);
>   }
> +#ifdef FIXMAP_PAGE_RO
> +void __init *
> +early_memremap_ro(resource_size_t phys_addr, unsigned long size)
> +{
> +	return (__force void *)__early_ioremap(phys_addr, size, FIXMAP_PAGE_RO);
> +}
> +#endif
>   #else /* CONFIG_MMU */
>
>   void __init __iomem *
> @@ -231,6 +238,11 @@ early_memremap(resource_size_t phys_addr, unsigned long size)
>   {
>   	return (void *)phys_addr;
>   }
> +void __init *
> +early_memremap_ro(resource_size_t phys_addr, unsigned long size)
> +{
> +	return (void *)phys_addr;
> +}
>
>   void __init early_iounmap(void __iomem *addr, unsigned long size)
>   {
>

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