From c021d44d0d4915a2b152d29abde5f1d4cb7b8ddd Mon Sep 17 00:00:00 2001

From: Alexander Graf <graf@amazon.com>

Date: Wed, 30 Sep 2020 23:10:53 +0200

Subject: [PATCH] nvme: Record maximum allowed request size

NVMe has a limit on how many sectors it can handle at most within a single

request. Remember that number, so that in a follow-up patch, we can verify

that we don't exceed it.

Signed-off-by: Alexander Graf <graf@amazon.com>

(cherry picked from commit b68f313c9139e480a9f5a0d1b5aa6f294b86d982)

---

 src/hw/nvme-int.h |  8 +++++++-

 src/hw/nvme.c     | 13 +++++++++++--

 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/src/hw/nvme-int.h b/src/hw/nvme-int.h

index 9f95dd8..674008a 100644

--- a/src/hw/nvme-int.h

+++ b/src/hw/nvme-int.h

@@ -117,6 +117,7 @@ struct nvme_namespace {

     u32 block_size;

     u32 metadata_size;

+    u32 max_req_size;

     /* Page aligned buffer of size NVME_PAGE_SIZE. */

     char *dma_buffer;

@@ -131,7 +132,12 @@ struct nvme_identify_ctrl {

     char mn[40];

     char fr[8];

-    char _boring[516 - 72];

+    u8 rab;

+    u8 ieee[3];

+    u8 cmic;

+    u8 mdts;

+

+    char _boring[516 - 78];

     u32 nn;                     /* number of namespaces */

 };

diff --git a/src/hw/nvme.c b/src/hw/nvme.c

index 6a01204..5bc2586 100644

--- a/src/hw/nvme.c

+++ b/src/hw/nvme.c

@@ -238,7 +238,8 @@ nvme_admin_identify_ns(struct nvme_ctrl *ctrl, u32 ns_id)

 }

 static void

-nvme_probe_ns(struct nvme_ctrl *ctrl, struct nvme_namespace *ns, u32 ns_id)

+nvme_probe_ns(struct nvme_ctrl *ctrl, struct nvme_namespace *ns, u32 ns_id,

+              u8 mdts)

 {

     ns->ctrl  = ctrl;

     ns->ns_id = ns_id;

@@ -281,6 +282,14 @@ nvme_probe_ns(struct nvme_ctrl *ctrl, struct nvme_namespace *ns, u32 ns_id)

     ns->drive.blksize   = ns->block_size;

     ns->drive.sectors   = ns->lba_count;

+    if (mdts) {

+        ns->max_req_size = ((1U << mdts) * NVME_PAGE_SIZE) / ns->block_size;

+        dprintf(3, "NVME NS %u max request size: %d sectors\n",

+                ns_id, ns->max_req_size);

+    } else {

+        ns->max_req_size = -1U;

+    }

+

     ns->dma_buffer = zalloc_page_aligned(&ZoneHigh, NVME_PAGE_SIZE);

     char *desc = znprintf(MAXDESCSIZE, "NVMe NS %u: %llu MiB (%llu %u-byte "

@@ -567,7 +576,7 @@ nvme_controller_enable(struct nvme_ctrl *ctrl)

     /* Populate namespace IDs */

     int ns_idx;

     for (ns_idx = 0; ns_idx < ctrl->ns_count; ns_idx++) {

-        nvme_probe_ns(ctrl, &ctrl->ns[ns_idx], ns_idx + 1);

+        nvme_probe_ns(ctrl, &ctrl->ns[ns_idx], ns_idx + 1, identify->mdts);

     }

     dprintf(3, "NVMe initialization complete!\n");