On Tue, Nov 15, 2016 at 12:29:35PM -0600, Tom Lendacky wrote: > On 11/15/2016 9:16 AM, Michael S. Tsirkin wrote: > > On Wed, Nov 09, 2016 at 06:37:23PM -0600, Tom Lendacky wrote: > >> Since DMA addresses will effectively look like 48-bit addresses when the > >> memory encryption mask is set, SWIOTLB is needed if the DMA mask of the > >> device performing the DMA does not support 48-bits. SWIOTLB will be > >> initialized to create un-encrypted bounce buffers for use by these devices. > >> > >> Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx> > >> --- > >> arch/x86/include/asm/dma-mapping.h | 5 ++- > >> arch/x86/include/asm/mem_encrypt.h | 5 +++ > >> arch/x86/kernel/pci-dma.c | 11 ++++--- > >> arch/x86/kernel/pci-nommu.c | 2 + > >> arch/x86/kernel/pci-swiotlb.c | 8 ++++- > >> arch/x86/mm/mem_encrypt.c | 17 +++++++++++ > >> include/linux/swiotlb.h | 1 + > >> init/main.c | 13 ++++++++ > >> lib/swiotlb.c | 58 +++++++++++++++++++++++++++++++----- > >> 9 files changed, 103 insertions(+), 17 deletions(-) > >> > >> diff --git a/arch/x86/include/asm/dma-mapping.h b/arch/x86/include/asm/dma-mapping.h > >> index 4446162..c9cdcae 100644 > >> --- a/arch/x86/include/asm/dma-mapping.h > >> +++ b/arch/x86/include/asm/dma-mapping.h > > ..SNIP... > > >> > >> +/* > >> + * If memory encryption is active, the DMA address for an encrypted page may > >> + * be beyond the range of the device. If bounce buffers are required be sure > >> + * that they are not on an encrypted page. This should be called before the > >> + * iotlb area is used. > > > > Makes sense, but I think at least a dmesg warning here > > might be a good idea. > > Good idea. Should it be a warning when it is first being set up or > a warning the first time the bounce buffers need to be used. Or maybe > both? > > > > > A boot flag that says "don't enable devices that don't support > > encryption" might be a good idea, too, since most people > > don't read dmesg output and won't notice the message. > > I'll look into this. It might be something that can be checked as > part of the device setting its DMA mask or the first time a DMA > API is used if the device doesn't explicitly set its mask. > > Thanks, > Tom > > > I think setup time is nicer if it's possible. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>