hw/block/nvme: fix pci doorbell size calculation

The size of the BAR is 0x1000 (main registers) + 8 bytes for each
queue. Currently, the size of the BAR is calculated like so:

    n->reg_size = pow2ceil(0x1004 + 2 * (n->num_queues + 1) * 4);

Since the 'num_queues' parameter already accounts for the admin queue,
this should in any case not need to be incremented by one. Also, the
size should be initialized to (0x1000).

    n->reg_size = pow2ceil(0x1000 + 2 * n->num_queues * 4);

This, with the default value of num_queues (64), we will set aside room
for 1 admin queue and 63 I/O queues (4 bytes per doorbell, 2 doorbells
per queue).

Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Message-Id: <20200609190333.59390-2-its@irrelevant.dk>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

diff --git a/hw/block/nvme.c b/hw/block/nvme.c
index a21eeca..c1476e8 100644 (file)
--- a/hw/block/nvme.c
+++ b/hw/block/nvme.c
@@ -53,6 +53,9 @@
 #include "trace.h"
 #include "nvme.h"
 
+#define NVME_REG_SIZE 0x1000
+#define NVME_DB_SIZE  4
+
 #define NVME_GUEST_ERR(trace, fmt, ...) \
     do { \
         (trace_##trace)(__VA_ARGS__); \
@@ -1401,7 +1404,9 @@ static void nvme_realize(PCIDevice *pci_dev, Error **errp)
     pcie_endpoint_cap_init(pci_dev, 0x80);
 
     n->num_namespaces = 1;
-    n->reg_size = pow2ceil(0x1004 + 2 * (n->num_queues + 1) * 4);
+
+    /* num_queues is really number of pairs, so each has two doorbells */
+    n->reg_size = pow2ceil(NVME_REG_SIZE + 2 * n->num_queues * NVME_DB_SIZE);
     n->ns_size = bs_size / (uint64_t)n->num_namespaces;
 
     n->namespaces = g_new0(NvmeNamespace, n->num_namespaces);