Re: [PATCH v6 24/34] x86, swiotlb: Add memory encryption support

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On 6/14/2017 11:45 AM, Borislav Petkov wrote:
On Wed, Jun 07, 2017 at 02:17:21PM -0500, Tom Lendacky wrote:
Since DMA addresses will effectively look like 48-bit addresses when the
memory encryption mask is set, SWIOTLB is needed if the DMA mask of the
device performing the DMA does not support 48-bits. SWIOTLB will be
initialized to create decrypted bounce buffers for use by these devices.

Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
---

...


diff --git a/init/main.c b/init/main.c
index df58a41..7125b5f 100644
--- a/init/main.c
+++ b/init/main.c
@@ -488,6 +488,10 @@ void __init __weak thread_stack_cache_init(void)
  }
  #endif
+void __init __weak mem_encrypt_init(void)
+{
+}

void __init __weak mem_encrypt_init(void) { }

saves some real estate. Please do that for the rest of the stubs you're
adding, for the next version.

Ok, will do.

Thanks,
Tom


+
  /*
   * Set up kernel memory allocators
   */
@@ -640,6 +644,15 @@ asmlinkage __visible void __init start_kernel(void)
  	 */
  	locking_selftest();
+ /*
+	 * This needs to be called before any devices perform DMA
+	 * operations that might use the SWIOTLB bounce buffers.
+	 * This call will mark the bounce buffers as decrypted so
+	 * that their usage will not cause "plain-text" data to be
+	 * decrypted when accessed.

s/This call/It/

+	 */
+	mem_encrypt_init();
+
  #ifdef CONFIG_BLK_DEV_INITRD
  	if (initrd_start && !initrd_below_start_ok &&
  	    page_to_pfn(virt_to_page((void *)initrd_start)) < min_low_pfn) {
diff --git a/lib/swiotlb.c b/lib/swiotlb.c
index a8d74a7..74d6557 100644
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -30,6 +30,7 @@
  #include <linux/highmem.h>
  #include <linux/gfp.h>
  #include <linux/scatterlist.h>
+#include <linux/mem_encrypt.h>
#include <asm/io.h>
  #include <asm/dma.h>
@@ -155,6 +156,17 @@ unsigned long swiotlb_size_or_default(void)
  	return size ? size : (IO_TLB_DEFAULT_SIZE);
  }
+void __weak swiotlb_set_mem_attributes(void *vaddr, unsigned long size)
+{
+}

As above.




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