[PATCH v2] iommu/io-pgtable-arm: Don't use dma_to_phys()
Russell King - ARM Linux
linux at arm.linux.org.uk
Fri Sep 18 05:29:37 PDT 2015
On Fri, Sep 18, 2015 at 12:04:26PM +0100, Robin Murphy wrote:
> Specifically, the problem case for that is when phys_addr_t is 64-bit but
> dma_addr_t is 32-bit. The cast in __arm_lpae_dma_addr is necessary to avoid
> a truncation warning when we make the DMA API calls, but we actually need
> the opposite in the comparison here - comparing the different types directly
> allows integer promotion to kick in appropriately so we don't lose the top
> half of the larger address. Otherwise, you'd never spot the difference
> between, say, your original page at 0x88c0000000 and a bounce-buffered copy
> that happened to end up mapped to 0xc0000000.
Hmm. Thinking about this, I think we ought to add to arch/arm/mm/Kconfig:
+ select ARCH_PHYS_ADDR_T_64BIT
I seem to remember that you're quite right that dma_addr_t <= phys_addr_t
but dma_addr_t must never be bigger than phys_addr_t.
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.
More information about the linux-arm-kernel