Re: [PATCH 1/2] x86: ioremap: fix wrong physical address handling

[Kenji Kaneshige]

(2010/06/17 13:22), H. Peter Anvin wrote:
> On 06/16/2010 07:50 PM, Matthew Wilcox wrote:
>> On Thu, Jun 17, 2010 at 10:30:06AM +0900, Kenji Kaneshige wrote:
>>> Index: linux-2.6.34/arch/x86/mm/ioremap.c
>>> ===================================================================
>>> --- linux-2.6.34.orig/arch/x86/mm/ioremap.c 2010-06-15 
>>> 04:43:00.978332015 +0900
>>> +++ linux-2.6.34/arch/x86/mm/ioremap.c 2010-06-15 05:32:59.291693007 
>>> +0900
>>> @@ -62,8 +62,8 @@
>>> static void __iomem *__ioremap_caller(resource_size_t phys_addr,
>>> unsigned long size, unsigned long prot_val, void *caller)
>>> {
>>> - unsigned long pfn, offset, vaddr;
>>> - resource_size_t last_addr;
>>> + unsigned long offset, vaddr;
>>> + resource_size_t pfn, last_pfn, last_addr;
>>
>> I have a hard time understanding this change. pfn is always a physical
>> address shifted by PAGE_SHIFT. So a 32-bit pfn supports up to 44-bit
>> physical addresses. Are your addresses above 44-bits?
>>
> 
> I think they might be. Kenji?

No. My addresses are in the 44-bits range (around fc000000000). So it is
not required for my problem. This change assumes that phys_addr can be
above 44-bits (up to 52-bits (and higher in the future?)).

By the way, is there linux kernel limit regarding above 44-bits physical
address in x86_32 PAE? For example, pfn above 32-bits is not supported?

#ifdef CONFIG_X86_PAE
/* 44=32+12, the limit we can fit into an unsigned long pfn */
#define __PHYSICAL_MASK_SHIFT   44
#define __VIRTUAL_MASK_SHIFT    32

If there is 44-bits physical address limit, I think it's better to use
PHYSICAL_PAGE_MASK for masking physical address, instead of "(phys_addr
>> PAGE_SHIFT) << PAGE_SHIFT)". The PHYSICAL_PAGE_MASK would become
greater value when 44-bits physical address limit is eliminated. And
maybe we need to change phys_addr_valid() returns error if physical
address is above (1 << __PHYSICAL_MASK_SHIFT)?

Thanks,
Kenji Kaneshige

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