[PATCH 3/6] ARM: mm: Drop the lowmem watermark check from virt_addr_valid()

[santosh.shilimkar@ti.com (Santosh Shilimkar)]

On Thursday 14 November 2013 07:22 PM, Christoffer Dall wrote:
> On Thu, Nov 14, 2013 at 02:37:43PM -0500, Santosh Shilimkar wrote:
>> Slab allocator can allocate memory beyond the lowmem watermark
>> which can lead to false failure of virt_addr_valid().
>>
>> So drop the check. The issue was seen with percpu_alloc()
>> in KVM code which was allocating memory beyond lowmem watermark.
>>
>> Am not completly sure whether this is the right fix and if it could
>> impact any other user of virt_addr_valid(). Without this fix as
>> pointed out the KVM init was failing in my testing.
>>
>> Cc: Christoffer Dall <christoffer.dall@linaro.org>
>> Cc: Marc Zyngier <marc.zyngier@arm.com>
>> Cc: Russell King <linux@arm.linux.org.uk>
>> Cc: Catalin Marinas <catalin.marinas@arm.com>
>> Cc: Will Deacon <will.deacon@arm.com>
>>
>> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
>> ---
>>  arch/arm/include/asm/memory.h |    3 +--
>>  1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h
>> index 4dd2145..412da47 100644
>> --- a/arch/arm/include/asm/memory.h
>> +++ b/arch/arm/include/asm/memory.h
>> @@ -343,8 +343,7 @@ static inline __deprecated void *bus_to_virt(unsigned long x)
>>  #define ARCH_PFN_OFFSET		PHYS_PFN_OFFSET
>>  
>>  #define virt_to_page(kaddr)	pfn_to_page(__pa(kaddr) >> PAGE_SHIFT)
>> -#define virt_addr_valid(kaddr)	((unsigned long)(kaddr) >= PAGE_OFFSET && (unsigned long)(kaddr) < (unsigned long)high_memory)
>> -
>> +#define virt_addr_valid(kaddr)	((unsigned long)(kaddr) >= PAGE_OFFSET)
>>  #endif
>>  
>>  #include <asm-generic/memory_model.h>
>> -- 
>> 1.7.9.5
>>
> 
> This looks wrong to me.  Check Documentation/arm/memory.txt, this would
> return true for the VMALLOC region, which would cause virt_to_phys to
> give you something invalid, which would be bad.
>
I also thought it might not be right fix and hence added a disclaimer
in the commit message ;-)
 
Regards,
Santosh