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Date: Fri, 17 Feb 2017 10:51:31 -0600 From: Tom Lendacky <thomas.lendacky@....com> To: Konrad Rzeszutek Wilk <konrad.wilk@...cle.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 2/17/2017 9:59 AM, Konrad Rzeszutek Wilk 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@....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. I thought the use of dma_set_mask() was mostly a one time probe/setup thing so I didn't think we would get that many of these messages. If dma_set_mask() is called much more often that that I can change this to a printk_ratelimit(). I'll look into it further. > >> + >> *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? It's meant just to notify the user about the condition. The user could then decide to use an alternative device that supports a greater DMA range (I can probably change it to a dev_warn_once() so that a device is identified). I would be nice if I could issue this message once per device that experienced this. I didn't see anything that would do that, though. Thanks, Tom >> + >> mask = dma_get_seg_boundary(hwdev); >> >> tbl_dma_addr &= mask; >>
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