From 414a4c93f1741b820597a746ff64d9cbc69d9f64 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Tue, 13 May 2025 09:06:49 +0200 Subject: [PATCH] nvme-pci: derive and better document max segments limits Redefine the max segments and max integrity limits based on the limiting factors. This keeps exactly the same values for 4k PAGE_SIZE systems, but increases the number of segments for larger page size as it properly derives the scatterlist allocation based limit for them instead of assuming a 4k PAGE_SIZE. Signed-off-by: Christoph Hellwig Reviewed-by: Keith Busch --- drivers/nvme/host/pci.c | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-) diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c index 1098eb17890b..94ed13903b1b 100644 --- a/drivers/nvme/host/pci.c +++ b/drivers/nvme/host/pci.c @@ -35,8 +35,6 @@ #define SQ_SIZE(q) ((q)->q_depth << (q)->sqes) #define CQ_SIZE(q) ((q)->q_depth * sizeof(struct nvme_completion)) -#define SGES_PER_PAGE (NVME_CTRL_PAGE_SIZE / sizeof(struct nvme_sgl_desc)) - /* Optimisation for I/Os between 4k and 128k */ #define NVME_SMALL_POOL_SIZE 256 @@ -45,10 +43,24 @@ * require an sg allocation that needs more than a page of data. */ #define NVME_MAX_KB_SZ 8192 -#define NVME_MAX_SEGS 128 -#define NVME_MAX_META_SEGS 15 #define NVME_MAX_NR_DESCRIPTORS 5 +/* + * For data SGLs we support a single descriptors worth of SGL entries, but for + * now we also limit it to avoid an allocation larger than PAGE_SIZE for the + * scatterlist. + */ +#define NVME_MAX_SEGS \ + min(NVME_CTRL_PAGE_SIZE / sizeof(struct nvme_sgl_desc), \ + (PAGE_SIZE / sizeof(struct scatterlist))) + +/* + * For metadata SGLs, only the small descriptor is supported, and the first + * entry is the segment descriptor, which for the data pointer sits in the SQE. + */ +#define NVME_MAX_META_SEGS \ + ((NVME_SMALL_POOL_SIZE / sizeof(struct nvme_sgl_desc)) - 1) + static int use_threaded_interrupts; module_param(use_threaded_interrupts, int, 0444); @@ -3829,8 +3841,6 @@ static int __init nvme_init(void) BUILD_BUG_ON(sizeof(struct nvme_create_sq) != 64); BUILD_BUG_ON(sizeof(struct nvme_delete_queue) != 64); BUILD_BUG_ON(IRQ_AFFINITY_MAX_SETS < 2); - BUILD_BUG_ON(NVME_MAX_SEGS > SGES_PER_PAGE); - BUILD_BUG_ON(sizeof(struct scatterlist) * NVME_MAX_SEGS > PAGE_SIZE); BUILD_BUG_ON(nvme_pci_npages_prp() > NVME_MAX_NR_DESCRIPTORS); return pci_register_driver(&nvme_driver); -- 2.50.1