[PATCH v2 10/19] x86, swiotlb: Teach swiotlb to skip "accepted" devices

[Dan Williams <dan.j.williams@intel.com>]

There are two mechanisms to force SWIOTLB operation, the kernel command
line option and the internal SWIOTLB_FORCE flag. With the arrival of
"accepted" devices, devices that have been enabled to DMA to private
encrypted memory, the SWIOTLB_FORCE flag is an awkward fit. It may be the
case that SWIOTLB operation wants to be forced regardless of the device
acceptance state.

Introduce a new SWIOTLB_UNACCPTED flag that allows for both augmenting the
result of is_swiotlb_force_bounce() dynamically and allowing for an "always
SWIOTLB" override.

Cc: Thomas Gleixner <tglx@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 include/linux/swiotlb.h   | 15 ++++++++++++---
 arch/x86/kernel/pci-dma.c |  2 +-
 kernel/dma/swiotlb.c      |  1 +
 3 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index 3dae0f592063..0efb9b8e5dd0 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -17,6 +17,7 @@ struct scatterlist;
 #define SWIOTLB_VERBOSE	(1 << 0) /* verbose initialization */
 #define SWIOTLB_FORCE	(1 << 1) /* force bounce buffering */
 #define SWIOTLB_ANY	(1 << 2) /* allow any memory for the buffer */
+#define SWIOTLB_UNACCEPTED (1 << 3) /* swiotlb for unaccepted devices */
 
 /*
  * Maximum allowable number of contiguous slabs to map,
@@ -91,6 +92,7 @@ struct io_tlb_pool {
  * @nslabs:	Total number of IO TLB slabs in all pools.
  * @debugfs:	The dentry to debugfs.
  * @force_bounce: %true if swiotlb bouncing is forced
+ * @bounce_unaccepted: %true if unaccepted devices must bounce
  * @for_alloc:  %true if the pool is used for memory allocation
  * @can_grow:	%true if more pools can be allocated dynamically.
  * @phys_limit:	Maximum allowed physical address.
@@ -109,8 +111,9 @@ struct io_tlb_mem {
 	struct io_tlb_pool defpool;
 	unsigned long nslabs;
 	struct dentry *debugfs;
-	bool force_bounce;
-	bool for_alloc;
+	u8 force_bounce:1;
+	u8 bounce_unaccepted:1;
+	u8 for_alloc:1;
 #ifdef CONFIG_SWIOTLB_DYNAMIC
 	bool can_grow;
 	u64 phys_limit;
@@ -173,7 +176,13 @@ static inline bool is_swiotlb_force_bounce(struct device *dev)
 {
 	struct io_tlb_mem *mem = dev->dma_io_tlb_mem;
 
-	return mem && mem->force_bounce;
+	if (!mem)
+		return false;
+	if (mem->force_bounce)
+		return true;
+	if (mem->bounce_unaccepted && !device_cc_accepted(dev))
+		return true;
+	return false;
 }
 
 void swiotlb_init(bool addressing_limited, unsigned int flags);
diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index 6267363e0189..8a737f501ae5 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -61,7 +61,7 @@ static void __init pci_swiotlb_detect(void)
 	 */
 	if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT)) {
 		x86_swiotlb_enable = true;
-		x86_swiotlb_flags |= SWIOTLB_FORCE;
+		x86_swiotlb_flags |= SWIOTLB_UNACCEPTED;
 	}
 }
 #else
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index a547c7693135..57e9647939fe 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -365,6 +365,7 @@ void __init swiotlb_init_remap(bool addressing_limit, unsigned int flags,
 
 	io_tlb_default_mem.force_bounce =
 		swiotlb_force_bounce || (flags & SWIOTLB_FORCE);
+	io_tlb_default_mem.bounce_unaccepted = flags & SWIOTLB_UNACCEPTED;
 
 #ifdef CONFIG_SWIOTLB_DYNAMIC
 	if (!remap)
-- 
2.52.0