Patch "iommu/amd: Fix the left value check of cmd buffer" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    iommu/amd: Fix the left value check of cmd buffer

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     iommu-amd-fix-the-left-value-check-of-cmd-buffer.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 432abf68a79332282329286d190e21fe3ac02a31 Mon Sep 17 00:00:00 2001
From: Huang Rui <ray.huang@amd.com>
Date: Mon, 12 Dec 2016 07:28:26 -0500
Subject: iommu/amd: Fix the left value check of cmd buffer

From: Huang Rui <ray.huang@amd.com>

commit 432abf68a79332282329286d190e21fe3ac02a31 upstream.

The generic command buffer entry is 128 bits (16 bytes), so the offset
of tail and head pointer should be 16 bytes aligned and increased with
0x10 per command.

When cmd buf is full, head = (tail + 0x10) % CMD_BUFFER_SIZE.

So when left space of cmd buf should be able to store only two
command, we should be issued one COMPLETE_WAIT additionally to wait
all older commands completed. Then the left space should be increased
after IOMMU fetching from cmd buf.

So left check value should be left <= 0x20 (two commands).

Signed-off-by: Huang Rui <ray.huang@amd.com>
Fixes: ac0ea6e92b222 ('x86/amd-iommu: Improve handling of full command buffer')
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/iommu/amd_iommu.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -926,7 +926,7 @@ again:
 	next_tail = (tail + sizeof(*cmd)) % CMD_BUFFER_SIZE;
 	left      = (head - next_tail) % CMD_BUFFER_SIZE;
 
-	if (left <= 2) {
+	if (left <= 0x20) {
 		struct iommu_cmd sync_cmd;
 		volatile u64 sem = 0;
 		int ret;


Patches currently in stable-queue which might be from ray.huang@amd.com are

queue-4.4/iommu-amd-fix-the-left-value-check-of-cmd-buffer.patch