On Fri, Jun 16, 2017 at 01:54:36PM -0500, Tom Lendacky wrote:
> Add warnings to let the user know when bounce buffers are being used for
> DMA when SME is active. Since the bounce buffers are not in encrypted
> memory, these notifications are to allow the user to determine some
> appropriate action - if necessary. Actions can range from utilizing an
> IOMMU, replacing the device with another device that can support 64-bit
> DMA, ignoring the message if the device isn't used much, etc.
>
> Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
> ---
> include/linux/dma-mapping.h | 11 +++++++++++
> include/linux/mem_encrypt.h | 8 ++++++++
> lib/swiotlb.c | 3 +++
> 3 files changed, 22 insertions(+)
>
> diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> index 4f3eece..ee2307e 100644
> --- a/include/linux/dma-mapping.h
> +++ b/include/linux/dma-mapping.h
> @@ -10,6 +10,7 @@
> #include <linux/scatterlist.h>
> #include <linux/kmemcheck.h>
> #include <linux/bug.h>
> +#include <linux/mem_encrypt.h>
>
> /**
> * List of possible attributes associated with a DMA mapping. The semantics
> @@ -577,6 +578,11 @@ static inline int dma_set_mask(struct device *dev, u64 mask)
>
> if (!dev->dma_mask || !dma_supported(dev, mask))
> return -EIO;
> +
> + /* Since mask is unsigned, this can only be true if SME is active */
> + if (mask < sme_dma_mask())
> + dev_warn(dev, "SME is active, device will require DMA bounce buffers\n");
> +
> *dev->dma_mask = mask;
> return 0;
> }
> @@ -596,6 +602,11 @@ static inline int dma_set_coherent_mask(struct device *dev, u64 mask)
> {
> if (!dma_supported(dev, mask))
> return -EIO;
> +
> + /* Since mask is unsigned, this can only be true if SME is active */
> + if (mask < sme_dma_mask())
> + dev_warn(dev, "SME is active, device will require DMA bounce buffers\n");
Looks to me like those two checks above need to be a:
void sme_check_mask(struct device *dev, u64 mask)
{
if (!sme_me_mask)
return;
/* Since mask is unsigned, this can only be true if SME is active */
if (mask < (((u64)sme_me_mask << 1) - 1))
dev_warn(dev, "SME is active, device will require DMA bounce buffers\n");
}
which gets called and sme_dma_mask() is not really needed.
--
Regards/Gruss,
Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
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