Re: [PATCH v3 3/6] iommu: add ARM short descriptor page table allocator.

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 




On Fri, Jul 31, 2015 at 08:55:37AM +0100, Yong Wu wrote:
>     About the AP bits, I may have to add a new quirk for it...
> 
>   Current I add AP in pte like this:
> #define ARM_SHORT_PTE_RD_WR        (3 << 4)
> #define ARM_SHORT_PTE_RDONLY       BIT(9)
> 
> pteprot |=  ARM_SHORT_PTE_RD_WR;
> 
> 
>  If(!(prot & IOMMU_WRITE) && (prot & IOMMU_READ))
> 
> 
>       pteprot |= ARM_SHORT_PTE_RDONLY;
> 
> The problem is that the BIT(9) in the level1 and level2 pagetable of our
> HW has been used for PA[32] that is for the dram size over 4G.

Aha, now *thats* a case of page-table abuse!

> so I had to add a quirk to disable bit9 while RDONLY case.
> (If BIT9 isn't disabled, the HW treat it as the PA[32] case then it will
> translation fault..)
> 
> like: IO_PGTABLE_QUIRK_SHORT_MTK ?

Given that you don't have XN either, maybe IO_PGTABLE_QUIRK_NO_PERMS?
When set, IOMMU_READ/WRITE/EXEC are ignored and the mapping will never
generate a permission fault.

Will
--
To unsubscribe from this list: send the line "unsubscribe devicetree" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html



[Index of Archives]     [Device Tree Compilter]     [Device Tree Spec]     [Linux Driver Backports]     [Video for Linux]     [Linux USB Devel]     [Linux PCI Devel]     [Linux Audio Users]     [Linux Kernel]     [Linux SCSI]     [XFree86]     [Yosemite Backpacking]
  Powered by Linux