iommu/amd: Fix the left value check of cmd buffer
authorHuang Rui <ray.huang@amd.com>
Mon, 12 Dec 2016 12:28:26 +0000 (07:28 -0500)
committerBen Hutchings <ben@decadent.org.uk>
Thu, 16 Mar 2017 02:18:39 +0000 (02:18 +0000)
commitb91096790d5018299d71164a18360c638bade3b8
tree851d1e5c0d55d7dc9a4f0379452a91f019bd068b
parent666d227806459ca178441873f3b1b57cda39e2af
iommu/amd: Fix the left value check of cmd buffer

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: Ben Hutchings <ben@decadent.org.uk>
drivers/iommu/amd_iommu.c