From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tom Lendacky Subject: Re: [RFC PATCH v4 19/28] swiotlb: Add warnings for use of bounce buffers with SME Date: Fri, 17 Feb 2017 10:51:31 -0600 Message-ID: <17c8099a-5495-5f1d-4c8a-bd9f5d2c5e58@amd.com> References: <20170216154158.19244.66630.stgit@tlendack-t1.amdoffice.net> <20170216154619.19244.76653.stgit@tlendack-t1.amdoffice.net> <20170217155955.GK30272@char.us.ORACLE.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20170217155955.GK30272-he5eyhs8q0A6W680SEFli9BPR1lH4CV8@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Konrad Rzeszutek Wilk Cc: linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Brijesh Singh , Toshimitsu Kani , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Matt Fleming , x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, Alexander Potapenko , "H. Peter Anvin" , Larry Woodman , linux-arch-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Jonathan Corbet , linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kasan-dev-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org, Ingo Molnar , Andrey Ryabinin , Rik van Riel , Arnd Bergmann , Borislav Petkov , Andy Lutomirski , Thomas Gleixner , Dmitry Vyukov , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, "Michael S. Tsirkin" , Paolo List-Id: iommu@lists.linux-foundation.org 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 >> --- >> 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 >> #include >> #include >> +#include >> >> /** >> * 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; >>