Re: [PATCH v2] Bugfix for handling of shadow doorbell buffer.
From: Sagi Grimberg
Date: Thu Aug 16 2018 - 17:20:14 EST
diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 17a0190bd88f..4452f8553301 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -306,6 +306,14 @@ static bool nvme_dbbuf_update_and_check_event(u16 value, u32 *dbbuf_db,
old_value = *dbbuf_db;
*dbbuf_db = value;
+ /*
+ * Ensure that the doorbell is updated before reading
+ * the EventIdx from memory. NVMe controller should have
+ * similar ordering guarantees - update EventIdx before
+ * reading doorbell.
+ */
+ mb();
+
if (!nvme_dbbuf_need_event(*dbbuf_ei, value, old_value))
return false;
}
Reviewed-by: Sagi Grimberg <sagi@xxxxxxxxxxx>