linux-kernel - Re: [PATCH 1/2] [Patch-next -v2] ACPI, APEI Fix the return value(==NULL) of acpi_pre

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Date:	Wed, 18 Aug 2010 12:16:58 +0800
From:	Huang Ying <ying.huang@...el.com>
To:	Jin Dongming <jin.dongming@...css.fujitsu.com>
Cc:	Randy Dunlap <randy.dunlap@...cle.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Andi Kleen <andi@...stfloor.org>,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	LKLM <linux-kernel@...r.kernel.org>,
	ACPI <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH 1/2] [Patch-next -v2] ACPI, APEI Fix the return
 value(==NULL) of acpi_pre_map().

On Wed, 2010-08-18 at 07:46 +0800, Jin Dongming wrote:
> acpi_pre_map() is used for remapping the physical address of I/O, so
> it should be return NULL or remapped virtual address. The problem is
> that when (paddr - pg_off) equals 0, no matter whether I/O remapping is
> successful or not, the function returns NULL.
> 
> In acpi_pre_map(), after the physical address is remapped sucessfully,
> it will check whether the physical address has been added into acpi_iomaps
> list again.
>    - If the physical address has beed added into acpi_iomaps, the virtual
>      address will be saved in vaddr.
>    - Otherwise, NULL be saved in vaddr.
> 
> So if the physical address is the first time to be remapped, vaddr will be
> NULL always.
> 
> In many cases, (paddr - pg_off) may not equal 0. So the function could work
> well. In our machine, (paddr - pg_off) equals 0, so the return value of
> acpi_pre_map() is NULL.
> 
> This patch fixed it and I confirmed it on x86_64 next-tree.
> 
> Signed-off-by: Jin Dongming <jin.dongming@...css.fujitsu.com>
Acked-by: Huang Ying <ying.huang@...el.com>

Best Regards,
Huang Ying


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