Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965117AbdCJOA5 (ORCPT ); Fri, 10 Mar 2017 09:00:57 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:42715 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934008AbdCJLvl (ORCPT ); Fri, 10 Mar 2017 06:51:41 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Joerg Roedel" , "Huang Rui" Date: Fri, 10 Mar 2017 11:46:22 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 176/370] iommu/amd: Fix the left value check of cmd buffer In-Reply-To: X-SA-Exim-Connect-IP: 82.70.136.246 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1341 Lines: 40 3.16.42-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Huang Rui 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: Ben Hutchings --- 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 @@ -1044,7 +1044,7 @@ again: next_tail = (tail + sizeof(*cmd)) % iommu->cmd_buf_size; left = (head - next_tail) % iommu->cmd_buf_size; - if (left <= 2) { + if (left <= 0x20) { struct iommu_cmd sync_cmd; volatile u64 sem = 0; int ret;