From 2148835de3c2410bfb6c64037187a1b72f6d6488 Mon Sep 17 00:00:00 2001 From: Huang Rui Date: Mon, 12 Dec 2016 07:28:26 -0500 Subject: 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 Fixes: ac0ea6e92b222 ('x86/amd-iommu: Improve handling of full command buffer') Signed-off-by: Joerg Roedel Signed-off-by: Greg Kroah-Hartman diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c index 754595e..11a13b5 100644 --- a/drivers/iommu/amd_iommu.c +++ b/drivers/iommu/amd_iommu.c @@ -1021,7 +1021,7 @@ 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; int ret; -- cgit v0.10.2