From: Tom Lendacky <thomas.lendacky@amd.com>
Date: Mon, 17 Jul 2017 16:10:22 -0500
Subject: swiotlb: Add warnings for use of bounce buffers with SME
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Git-commit: 648babb7078c6310d2af5b8aa01f086030916968
Patch-mainline: v4.14-rc1
References: fate#322123

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>
Acked-by: Borislav Petkov <bp@suse.de>
---
 include/linux/dma-mapping.h |   13 +++++++++++++
 lib/swiotlb.c               |    3 +++
 2 files changed, 16 insertions(+)

--- 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
@@ -554,6 +555,12 @@ static inline int dma_mapping_error(stru
 #endif
 }
 
+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");
+}
+
 #ifndef HAVE_ARCH_DMA_SUPPORTED
 static inline int dma_supported(struct device *dev, u64 mask)
 {
@@ -577,6 +584,9 @@ static inline int dma_set_mask(struct de
 
 	if (!dev->dma_mask || !dma_supported(dev, mask))
 		return -EIO;
+
+	dma_check_mask(dev, mask);
+
 	*dev->dma_mask = mask;
 	return 0;
 }
@@ -596,6 +606,9 @@ static inline int dma_set_coherent_mask(
 {
 	if (!dma_supported(dev, mask))
 		return -EIO;
+
+	dma_check_mask(dev, mask);
+
 	dev->coherent_dma_mask = mask;
 	return 0;
 }
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -507,6 +507,9 @@ phys_addr_t swiotlb_tbl_map_single(struc
 	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;