linux-kernel - [PATCH 1/2] scsi: vmw_pvscsi: Fix swiotlb operation

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Message-Id: <20191121115204.53060-1-thomas_os@shipmail.org>
Date:   Thu, 21 Nov 2019 12:52:03 +0100
From:   Thomas Hellström (VMware) 
        <thomas_os@...pmail.org>
To:     linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        pv-drivers@...are.com
Cc:     Thomas Hellstrom <thellstrom@...are.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Vishal Bhakta <vbhakta@...are.com>, Jim Gill <jgill@...are.com>
Subject: [PATCH 1/2] scsi: vmw_pvscsi: Fix swiotlb operation

From: Thomas Hellstrom <thellstrom@...are.com>

With swiotlb, the first byte of the sense buffer may in some cases be
uninitialized since we use DMA_FROM_DEVICE, and the device incorrectly
doesn't clear it. In those cases, clear it after DMA unmapping.

Cc: "James E.J. Bottomley" <jejb@...ux.ibm.com>
Cc: "Martin K. Petersen" <martin.petersen@...cle.com>
Suggested-by: Vishal Bhakta <vbhakta@...are.com>
Signed-off-by: Thomas Hellstrom <thellstrom@...are.com>
Acked-by: Jim Gill <jgill@...are.com>

 Please enter the commit message for your changes. Lines starting
---
 drivers/scsi/vmw_pvscsi.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/scsi/vmw_pvscsi.c b/drivers/scsi/vmw_pvscsi.c
index 70008816c91f..8a09d184a320 100644
--- a/drivers/scsi/vmw_pvscsi.c
+++ b/drivers/scsi/vmw_pvscsi.c
@@ -402,6 +402,17 @@ static int pvscsi_map_buffers(struct pvscsi_adapter *adapter,
 	return 0;
 }
 
+/*
+ * The device incorrectly doesn't clear the first byte of the sense
+ * buffer in some cases. We have to do it ourselves.
+ * Otherwise we run into trouble when SWIOTLB is forced.
+ */
+static void pvscsi_patch_sense(struct scsi_cmnd *cmd)
+{
+	if (cmd->sense_buffer)
+		cmd->sense_buffer[0] = 0;
+}
+
 static void pvscsi_unmap_buffers(const struct pvscsi_adapter *adapter,
 				 struct pvscsi_ctx *ctx)
 {
@@ -544,6 +555,8 @@ static void pvscsi_complete_request(struct pvscsi_adapter *adapter,
 	cmd = ctx->cmd;
 	abort_cmp = ctx->abort_cmp;
 	pvscsi_unmap_buffers(adapter, ctx);
+	if (sdstat != SAM_STAT_CHECK_CONDITION)
+		pvscsi_patch_sense(cmd);
 	pvscsi_release_context(adapter, ctx);
 	if (abort_cmp) {
 		/*
@@ -873,6 +886,7 @@ static void pvscsi_reset_all(struct pvscsi_adapter *adapter)
 			scmd_printk(KERN_ERR, cmd,
 				    "Forced reset on cmd %p\n", cmd);
 			pvscsi_unmap_buffers(adapter, ctx);
+			pvscsi_patch_sense(cmd);
 			pvscsi_release_context(adapter, ctx);
 			cmd->result = (DID_RESET << 16);
 			cmd->scsi_done(cmd);
-- 
2.21.0