[PATCH v2] ARM: mm: Get rid of L_PTE_USER ref from PAGE_S2_DEVICE

[Christoffer Dall]

On Sat, May 25, 2013 at 3:02 AM, Marc Zyngier <maz at misterjones.org> wrote:
> On Fri, 24 May 2013 18:12:39 -0700, Christoffer Dall
> <cdall at cs.columbia.edu> wrote:
>> THe L_PTE_USER actually has nothing to do with stage 2 mappings and the
>> L_PTE_S2_RDWR value sets the readable bit, which was what L_PTE_USER
>> was used for before proper handling of stage 2 memory defines.
>>
>> Changelog:
>>  [v2]: Change default mappings to be r/w instead of r/o, as per Marc
>>        Zyngier's suggestion.
>>
>> Cc: Marc Zyngier <marc.zyngier at arm.com>
>> Signed-off-by: Christoffer Dall <cdall at cs.columbia.edu>
>> ---
>>  arch/arm/include/asm/pgtable.h |    2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/arm/include/asm/pgtable.h
>> b/arch/arm/include/asm/pgtable.h
>> index 9bcd262..8afc60c 100644
>> --- a/arch/arm/include/asm/pgtable.h
>> +++ b/arch/arm/include/asm/pgtable.h
>> @@ -97,7 +97,7 @@ extern pgprot_t             pgprot_s2_device;
>>  #define PAGE_HYP             _MOD_PROT(pgprot_kernel, L_PTE_HYP)
>>  #define PAGE_HYP_DEVICE              _MOD_PROT(pgprot_hyp_device, L_PTE_HYP)
>>  #define PAGE_S2                      _MOD_PROT(pgprot_s2, L_PTE_S2_RDONLY)
>> -#define PAGE_S2_DEVICE               _MOD_PROT(pgprot_s2_device, L_PTE_USER |
>> L_PTE_S2_RDONLY)
>> +#define PAGE_S2_DEVICE               _MOD_PROT(pgprot_s2_device, L_PTE_S2_RDWR)
>>
>>  #define __PAGE_NONE          __pgprot(_L_PTE_DEFAULT | L_PTE_RDONLY | L_PTE_XN
> |
>>  L_PTE_NONE)
>>  #define __PAGE_SHARED                __pgprot(_L_PTE_DEFAULT | L_PTE_USER | L_PTE_XN)
>
> Actually, there's a much better solution.
>
> Just get rid of PAGE_S2_DEVICE altogether, as it is completely useless. We
> never have to enforce a memory type in S2 that is stronger than the guest's
> view. If the guest insists on doing something silly (mapping a device as
> normal memory, for example), we really don't have to fix things for them.
>
> See the patch I posted a while ago as part of my pending fixes series:
> https://lists.cs.columbia.edu/pipermail/kvmarm/2013-May/005827.html
>
yeah duh, I'll reply to that one.