OK, we'll make the change for D0x too. Thanks,
Heyi On 30 October 2017 at 23:17, Ard Biesheuvel <ard.biesheu...@linaro.org> wrote: > On 30 October 2017 at 15:13, Heyi Guo <heyi....@linaro.org> wrote: > > Hi Ard, > > > > > > On 10/30/2017 04:21 PM, Ard Biesheuvel wrote: > >> > >> On 30 October 2017 at 03:52, Heyi Guo <heyi....@linaro.org> wrote: > >>> > >>> Hi folks, > >>> > >>> In NonDiscoverablePciDeviceDxe driver, NonCoherentPciIoAllocateBuffer > may > >>> allocate EFI_MEMORY_UC buffer depending on input Attributes and GCD > >>> capabilities. If it does, it actually allocates memory of "device" type > >>> in > >>> AArch64, but not "normal uncacheable" memory. For "device" memory type, > >>> it > >>> requires restrict access alignment and it may trigger alignment fault > >>> exception with BaseMemoryLibOptDxe in which read/write alignment is not > >>> guaranteed. > >>> > >>> Is EFI_MOMORY_WC enough for AArch64 platforms? How about other > platforms, > >>> like X86? > >>> > >> Hello Heyi, > >> > >> Do you mean EFI_MEMORY_UC in the last sentence? If not, I don't > >> understand the question. > > > > I actually meant EFI_MOMORY_WC for I supposed EFI_MOMORY_WC should be > enough > > for AArch64 non cacheable DMA access. > > > >> > >> Anyway, in reality, this code will only allocate EFI_MEMORY_UC memory > >> if any memory already exists in the memory map with that capability, > >> otherwise it will fall back to EFI_MEMORY_WC. On most arm64 platforms, > >> we no longer add this capability to system memoryEFI_MOMORY_WC by > default, > >> so you > >> should be getting EFI_MEMORY_WC in most cases. > > > > > > Oh, I supposed we always have UC capability for system memory and we > > actually still do that on D0x platforms. Does it mean we'd better remove > > this capability to get the issue fixed? > > Yes. > > > Is there any architectural reason > > for not setting UC capability on system memory? > > > > Yes, exactly the reasons you mention: memory no longer behaves as > memory if you map it with EFI_MEMORY_UC attributes, i.e., unaligned > accesses or DC ZVA instructions can no longer be used. > _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
