[PATCH 4/6] nvme: Add a quirk for page aligned admin queue buffers

[Sven Peter]

Apple controllers seem to require any queue buffers on the admin queue
to be aligned to the NVMe controller page size. Weirdly, this constraint
does not apply to the i/o queue where any alignment is fine. This has
always been required on pre-M1 controllers and is required starting with
macOS 15 firmware or post-M4 controllers again. On M1/M2/M3 we only got
away with this because there was a chicken bit to disable this
requirement. Let's add a quirk that enforces this alignment.

Signed-off-by: Sven Peter <sven at kernel.org>
---
 drivers/nvme/host/core.c | 5 ++++-
 drivers/nvme/host/nvme.h | 7 +++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 453c1f0b2dd0..b76f4e4d8850 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -2071,7 +2071,10 @@ static void nvme_set_ctrl_limits(struct nvme_ctrl *ctrl,
 	lim->max_integrity_segments = ctrl->max_integrity_segments;
 	lim->virt_boundary_mask = ctrl->ops->get_virt_boundary(ctrl, is_admin);
 	lim->max_segment_size = UINT_MAX;
-	lim->dma_alignment = 3;
+	if (is_admin && (ctrl->quirks & NVME_QUIRK_ADMIN_PAGE_ALIGN))
+		lim->dma_alignment = NVME_CTRL_PAGE_SIZE - 1;
+	else
+		lim->dma_alignment = 3;
 }
 
 static bool nvme_update_disk_info(struct nvme_ns *ns, struct nvme_id_ns *id,
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 824651cc898d..957ded0c6f53 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -178,6 +178,11 @@ enum nvme_quirks {
 	 * Align dma pool segment size to 512 bytes
 	 */
 	NVME_QUIRK_DMAPOOL_ALIGN_512		= (1 << 22),
+
+	/*
+	 * Admin queue DMA buffers must be page aligned
+	 */
+	NVME_QUIRK_ADMIN_PAGE_ALIGN		= (1 << 23),
 };
 
 static inline char *nvme_quirk_name(enum nvme_quirks q)
@@ -229,6 +234,8 @@ static inline char *nvme_quirk_name(enum nvme_quirks q)
 		return "broken_msi";
 	case NVME_QUIRK_DMAPOOL_ALIGN_512:
 		return "dmapool_align_512";
+	case NVME_QUIRK_ADMIN_PAGE_ALIGN:
+		return "admin_page_align";
 	}
 
 	return "unknown";

-- 
2.55.0