From: Eduard Hasenleithner <eduard@hasenleithner.at>

Date: Tue, 12 Nov 2019 21:55:01 +0100

Subject: [PATCH] nvme: Discard workaround for non-conformant devices

Git-commit: 530436c45ef2e446c12538a400e465929a0b3ade

Patch-mainline: v5.5-rc1

References: bsc#1169045

Users observe IOMMU related errors when performing discard on nvme from

non-compliant nvme devices reading beyond the end of the DMA mapped

ranges to discard.

Two different variants of this behavior have been observed: SM22XX

controllers round up the read size to a multiple of 512 bytes, and Phison

E12 unconditionally reads the maximum discard size allowed by the spec

(256 segments or 4kB).

Make nvme_setup_discard unconditionally allocate the maximum DSM buffer

so the driver DMA maps a memory range that will always succeed.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=202665 many

Signed-off-by: Eduard Hasenleithner <eduard@hasenleithner.at>

[changelog, use existing define, kernel coding style]

Signed-off-by: Keith Busch <kbusch@kernel.org>

Acked-by: Hannes Reinecke <hare@suse.com>

---

 drivers/nvme/host/core.c | 12 +++++++++---

 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c

index 4be64703aa47..9696404a6182 100644

--- a/drivers/nvme/host/core.c

+++ b/drivers/nvme/host/core.c

@@ -574,8 +574,14 @@ static blk_status_t nvme_setup_discard(struct nvme_ns *ns, struct request *req,

 	struct nvme_dsm_range *range;

 	struct bio *bio;

-	range = kmalloc_array(segments, sizeof(*range),

-				GFP_ATOMIC | __GFP_NOWARN);

+	/*

+	 * Some devices do not consider the DSM 'Number of Ranges' field when

+	 * determining how much data to DMA. Always allocate memory for maximum

+	 * number of segments to prevent device reading beyond end of buffer.

+	 */

+	static const size_t alloc_size = sizeof(*range) * NVME_DSM_MAX_RANGES;

+

+	range = kzalloc(alloc_size, GFP_ATOMIC | __GFP_NOWARN);

 	if (!range) {

 		/*

 		 * If we fail allocation our range, fallback to the controller

@@ -615,7 +621,7 @@ static blk_status_t nvme_setup_discard(struct nvme_ns *ns, struct request *req,

 	req->special_vec.bv_page = virt_to_page(range);

 	req->special_vec.bv_offset = offset_in_page(range);

-	req->special_vec.bv_len = sizeof(*range) * segments;

+	req->special_vec.bv_len = alloc_size;

 	req->rq_flags |= RQF_SPECIAL_PAYLOAD;

 	return BLK_STS_OK;

-- 

2.16.4