swiotlb: Add warnings for use of bounce buffers with SME

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.  Actions can range from utilizing an
IOMMU, replacing the device with another device that can support 64-bit
DMA, ignoring the message if the device isn't used much, etc.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Larry Woodman <lwoodman@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Toshimitsu Kani <toshi.kani@hpe.com>
Cc: kasan-dev@googlegroups.com
Cc: kvm@vger.kernel.org
Cc: linux-arch@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-efi@vger.kernel.org
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/d112564053c3f2e86ca634a8d4fa4abc0eb53a6a.1500319216.git.thomas.lendacky@amd.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 843ab866e0f487c2000e0974592ee98544293758..fce2369ecf82b9db86b4944c7268006fed7f34cb 100644 (file)
--- 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
@@ -548,6 +549,12 @@ static inline int dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
        return 0;
 }
 
+static inline void dma_check_mask(struct device *dev, u64 mask)
+{
+       if (sme_active() && (mask < (((u64)sme_get_me_mask() << 1) - 1)))
+               dev_warn(dev, "SME is active, device will require DMA bounce buffers\n");
+}
+
 static inline int dma_supported(struct device *dev, u64 mask)
 {
        const struct dma_map_ops *ops = get_dma_ops(dev);
@@ -564,6 +571,9 @@ static inline int dma_set_mask(struct device *dev, u64 mask)
 {
        if (!dev->dma_mask || !dma_supported(dev, mask))
                return -EIO;
+
+       dma_check_mask(dev, mask);
+
        *dev->dma_mask = mask;
        return 0;
 }
@@ -583,6 +593,9 @@ static inline int dma_set_coherent_mask(struct device *dev, u64 mask)
 {
        if (!dma_supported(dev, mask))
                return -EIO;
+
+       dma_check_mask(dev, mask);
+
        dev->coherent_dma_mask = mask;
        return 0;
 }

diff --git a/lib/swiotlb.c b/lib/swiotlb.c
index 04ac91acf193058442fdf76f13be26c0bdc9d6e4..8c6c83ef57a43336e0a33a52f691e3323eb8f3f4 100644 (file)
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -507,6 +507,9 @@ 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");
 
+       if (sme_active())
+               pr_warn_once("SME is active and system is using DMA bounce buffers\n");
+
        mask = dma_get_seg_boundary(hwdev);
 
        tbl_dma_addr &= mask;