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@xxxxxxx> --- 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;
