nvme: Discard workaround for non-conformant devices (530436c4) · Commits · 戴 / test

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>

drivers/nvme/host/core.c

+9 −3

Original line number	Diff line number	Diff line
		@@ -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;

Admin message