commit c92a54cfa0257e8ffd66b2a17d49e9c0bd4b769f upstream

This fix appears in 4.20, but dma_direct_supported() was changed in 4.20 such that the original version of the fix will not apply to previous versions of the kernel. The fix only applies to the 4.19-stable tree and has been backported for that tree.

The dma_direct_supported() function intends to check the DMA mask against specific values. However, the phys_to_dma() function includes the SME encryption mask, which defeats the intended purpose of the check. This results in drivers that support less than 48-bit DMA (SME encryption mask is bit 47) from being able to set the DMA mask successfully when SME is active, which results in the driver failing to initialize.

Change the function used to check the mask from phys_to_dma() to __phys_to_dma() so that the SME encryption mask is not part of the check.

Fixes: c1d0af1a1d5d ("kernel/dma/direct: take DMA offset into account in dma_direct_supported") Cc: stable@vger.kernel.org # 4.19.x Signed-off-by: Tom Lendacky thomas.lendacky@amd.com --- kernel/dma/direct.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c index de87b02..1d2f147 100644 --- a/kernel/dma/direct.c +++ b/kernel/dma/direct.c @@ -168,7 +168,12 @@ int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents, int dma_direct_supported(struct device *dev, u64 mask) { #ifdef CONFIG_ZONE_DMA - if (mask < phys_to_dma(dev, DMA_BIT_MASK(ARCH_ZONE_DMA_BITS))) + /* + * This check needs to be against the actual bit mask value, so + * use __phys_to_dma() here so that the SME encryption mask isn't + * part of the check. + */ + if (mask < __phys_to_dma(dev, DMA_BIT_MASK(ARCH_ZONE_DMA_BITS))) return 0; #else /* @@ -176,8 +181,12 @@ int dma_direct_supported(struct device *dev, u64 mask) * to be able to satisfy them - either by not supporting more physical * memory, or by providing a ZONE_DMA32. If neither is the case, the * architecture needs to use an IOMMU instead of the direct mapping. + * + * This check needs to be against the actual bit mask value, so + * use __phys_to_dma() here so that the SME encryption mask isn't + * part of the check. */ - if (mask < phys_to_dma(dev, DMA_BIT_MASK(32))) + if (mask < __phys_to_dma(dev, DMA_BIT_MASK(32))) return 0; #endif /*