Messages in this thread | | | Subject | Re: [RFC PATCH v4 19/28] swiotlb: Add warnings for use of bounce buffers with SME | From | Tom Lendacky <> | Date | Tue, 28 Feb 2017 17:19:51 -0600 |
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On 2/27/2017 11:52 AM, Borislav Petkov wrote: > On Thu, Feb 16, 2017 at 09:46:19AM -0600, 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. >> >> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com> >> --- >> arch/x86/include/asm/mem_encrypt.h | 11 +++++++++++ >> include/linux/dma-mapping.h | 11 +++++++++++ >> include/linux/mem_encrypt.h | 6 ++++++ >> lib/swiotlb.c | 3 +++ >> 4 files changed, 31 insertions(+) >> >> diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h >> index 87e816f..5a17f1b 100644 >> --- a/arch/x86/include/asm/mem_encrypt.h >> +++ b/arch/x86/include/asm/mem_encrypt.h >> @@ -26,6 +26,11 @@ static inline bool sme_active(void) >> return (sme_me_mask) ? true : false; >> } >> >> +static inline u64 sme_dma_mask(void) >> +{ >> + return ((u64)sme_me_mask << 1) - 1; >> +} >> + >> void __init sme_early_encrypt(resource_size_t paddr, >> unsigned long size); >> void __init sme_early_decrypt(resource_size_t paddr, >> @@ -53,6 +58,12 @@ static inline bool sme_active(void) >> { >> return false; >> } >> + >> +static inline u64 sme_dma_mask(void) >> +{ >> + return 0ULL; >> +} >> + >> #endif >> >> static inline void __init sme_early_encrypt(resource_size_t paddr, >> diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h >> index 10c5a17..130bef7 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 >> @@ -557,6 +558,11 @@ static inline int dma_set_mask(struct device *dev, u64 mask) >> >> if (!dev->dma_mask || !dma_supported(dev, mask)) >> return -EIO; >> + >> + if (sme_active() && (mask < sme_dma_mask())) >> + dev_warn(dev, >> + "SME is active, device will require DMA bounce buffers\n"); >> + > > Yes, definitely _once() here.
Setting the mask is a probe/init type event, so I think not having the _once() would be better so that all devices that set a mask to something less than the SME encryption mask would be identified. This isn't done for every DMA, etc.
> > It could be extended later to be per-device if the need arises. > > Also, a bit above in this function, we test if (ops->set_dma_mask) so > device drivers which supply even an empty ->set_dma_mask will circumvent > this check. > > It probably doesn't matter all that much right now because the > only driver I see right now defining this method, though, is > ethernet/intel/fm10k/fm10k_pf.c and some other arches' functionality > which is unrelated here.
Device drivers don't supply set_dma_mask() since that is part of the dma_map_ops structure. The fm10k_pf.c file function is unrelated to this (it's part of an internal driver structure). The dma_map_ops structure is setup by the arch or an iommu.
Thanks, Tom
> > But still... > >
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