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Date: Fri, 17 Feb 2017 10:59:55 -0500 From: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com> To: Tom Lendacky <thomas.lendacky@....com> Cc: linux-arch@...r.kernel.org, linux-efi@...r.kernel.org, kvm@...r.kernel.org, linux-doc@...r.kernel.org, x86@...nel.org, linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com, linux-mm@...ck.org, iommu@...ts.linux-foundation.org, Rik van Riel <riel@...hat.com>, Radim Krčmář <rkrcmar@...hat.com>, Toshimitsu Kani <toshi.kani@....com>, Arnd Bergmann <arnd@...db.de>, Jonathan Corbet <corbet@....net>, Matt Fleming <matt@...eblueprint.co.uk>, "Michael S. Tsirkin" <mst@...hat.com>, Joerg Roedel <joro@...tes.org>, Paolo Bonzini <pbonzini@...hat.com>, Brijesh Singh <brijesh.singh@....com>, Ingo Molnar <mingo@...hat.com>, Alexander Potapenko <glider@...gle.com>, Andy Lutomirski <luto@...nel.org>, "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>, Andrey Ryabinin <aryabinin@...tuozzo.com>, Thomas Gleixner <tglx@...utronix.de>, Larry Woodman <lwoodman@...hat.com>, Dmitry Vyukov <dvyukov@...gle.com> Subject: Re: [RFC PATCH v4 19/28] swiotlb: Add warnings for use of bounce buffers with SME 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@....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"); You can make it one line. But I am wondering if you should use printk_ratelimit as this may fill the console up. > + > *dev->dma_mask = mask; > return 0; > } > @@ -576,6 +582,11 @@ static inline int dma_set_coherent_mask(struct device *dev, u64 mask) > { > if (!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"); Ditto. > + > dev->coherent_dma_mask = mask; > return 0; > } > diff --git a/include/linux/mem_encrypt.h b/include/linux/mem_encrypt.h > index 14a7b9f..6829ff1 100644 > --- a/include/linux/mem_encrypt.h > +++ b/include/linux/mem_encrypt.h > @@ -28,6 +28,12 @@ static inline bool sme_active(void) > { > return false; > } > + > +static inline u64 sme_dma_mask(void) > +{ > + return 0ULL; > +} > + > #endif > > #endif /* CONFIG_AMD_MEM_ENCRYPT */ > diff --git a/lib/swiotlb.c b/lib/swiotlb.c > index c463067..aff9353 100644 > --- a/lib/swiotlb.c > +++ b/lib/swiotlb.c > @@ -509,6 +509,9 @@ phys_addr_t swiotlb_tbl_map_single(struct device *hwdev, > if (no_iotlb_memory) > panic("Can not allocate SWIOTLB buffer earlier and can't now provide you with the DMA bounce buffer"); > > + WARN_ONCE(sme_active(), > + "SME is active and system is using DMA bounce buffers\n"); How does that help? As in what can the user do with this? > + > mask = dma_get_seg_boundary(hwdev); > > tbl_dma_addr &= mask; >
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