linux-kernel - [PATCH 4.4 19/47] vmw_balloon: VMCI_DOORBELL

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Date:   Fri,  7 Sep 2018 23:10:15 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Xavier Deguillard <xdeguillard@...are.com>,
        Nadav Amit <namit@...are.com>
Subject: [PATCH 4.4 19/47] vmw_balloon: VMCI_DOORBELL_SET does not check status

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Nadav Amit <namit@...are.com>

commit ce664331b2487a5d244a51cbdd8cb54f866fbe5d upstream.

When vmballoon_vmci_init() sets a doorbell using VMCI_DOORBELL_SET, for
some reason it does not consider the status and looks at the result.
However, the hypervisor does not update the result - it updates the
status. This might cause VMCI doorbell not to be enabled, resulting in
degraded performance.

Fixes: 48e3d668b790 ("VMware balloon: Enable notification via VMCI")
Cc: stable@...r.kernel.org
Reviewed-by: Xavier Deguillard <xdeguillard@...are.com>
Signed-off-by: Nadav Amit <namit@...are.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/misc/vmw_balloon.c |   37 +++++++++++++++++++------------------
 1 file changed, 19 insertions(+), 18 deletions(-)

--- a/drivers/misc/vmw_balloon.c
+++ b/drivers/misc/vmw_balloon.c
@@ -1036,29 +1036,30 @@ static void vmballoon_vmci_cleanup(struc
  */
 static int vmballoon_vmci_init(struct vmballoon *b)
 {
-	int error = 0;
+	unsigned long error, dummy;
 
-	if ((b->capabilities & VMW_BALLOON_SIGNALLED_WAKEUP_CMD) != 0) {
-		error = vmci_doorbell_create(&b->vmci_doorbell,
-				VMCI_FLAG_DELAYED_CB,
-				VMCI_PRIVILEGE_FLAG_RESTRICTED,
-				vmballoon_doorbell, b);
-
-		if (error == VMCI_SUCCESS) {
-			VMWARE_BALLOON_CMD(VMCI_DOORBELL_SET,
-					b->vmci_doorbell.context,
-					b->vmci_doorbell.resource, error);
-			STATS_INC(b->stats.doorbell_set);
-		}
-	}
+	if ((b->capabilities & VMW_BALLOON_SIGNALLED_WAKEUP_CMD) == 0)
+		return 0;
 
-	if (error != 0) {
-		vmballoon_vmci_cleanup(b);
+	error = vmci_doorbell_create(&b->vmci_doorbell, VMCI_FLAG_DELAYED_CB,
+				     VMCI_PRIVILEGE_FLAG_RESTRICTED,
+				     vmballoon_doorbell, b);
 
-		return -EIO;
-	}
+	if (error != VMCI_SUCCESS)
+		goto fail;
+
+	error = VMWARE_BALLOON_CMD(VMCI_DOORBELL_SET, b->vmci_doorbell.context,
+				   b->vmci_doorbell.resource, dummy);
+
+	STATS_INC(b->stats.doorbell_set);
+
+	if (error != VMW_BALLOON_SUCCESS)
+		goto fail;
 
 	return 0;
+fail:
+	vmballoon_vmci_cleanup(b);
+	return -EIO;
 }
 
 /*