[PATCH 1/2] hw/block/nvme: add msix_qsize parameter

[Klaus Jensen]

From: Klaus Jensen <k.jensen@samsung.com>

Commit 4eb9f5217a16 ("hw/block/nvme: allow use of any valid msix
vector") erronously allows any valid MSI-X vector to be used when
creating completion queues. This is bad because MSI-X is initialized
with max_ioqpairs + 1 vectors, which defaults to 64 + 1. And since
commit ccd579b2ed03 ("hw/block/nvme: Verify msix_vector_use() returned
value"), this also causes an assert if the host creates a completion
queue with an invalid vector.

Fix this by decoupling the requested maximum number of ioqpairs (param
max_ioqpairs) from the number of MSI-X interrupt vectors by introducing
a new msix_qsize parameter and initialize MSI-X with that. This allows
emulating a device that has fewer vectors than I/O queue pairs and also
allows more than 2048 queue pairs. To get the same default behaviour as
previously, msix_qsize defaults to 65 (max_ioqpairs default + 1).

This decoupling was actually suggested by Maxim some time ago in a
slightly different context, so adding a Suggested-by.

Fixes: 4eb9f5217a16 ("hw/block/nvme: allow use of any valid msix vector")
Suggested-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
---
 hw/block/nvme.c | 17 +++++++++++++----
 hw/block/nvme.h |  1 +
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/hw/block/nvme.c b/hw/block/nvme.c
index 567bce75191a..acc6dbc900e2 100644
--- a/hw/block/nvme.c
+++ b/hw/block/nvme.c
@@ -54,6 +54,7 @@
 #include "trace.h"
 #include "nvme.h"
 
+#define NVME_MAX_IOQPAIRS 0xffff
 #define NVME_REG_SIZE 0x1000
 #define NVME_DB_SIZE  4
 #define NVME_CMB_BIR 2
@@ -662,7 +663,7 @@ static uint16_t nvme_create_cq(NvmeCtrl *n, NvmeCmd *cmd)
         trace_pci_nvme_err_invalid_create_cq_vector(vector);
         return NVME_INVALID_IRQ_VECTOR | NVME_DNR;
     }
-    if (unlikely(vector > PCI_MSIX_FLAGS_QSIZE)) {
+    if (unlikely(vector >= n->params.msix_qsize)) {
         trace_pci_nvme_err_invalid_create_cq_vector(vector);
         return NVME_INVALID_IRQ_VECTOR | NVME_DNR;
     }
@@ -1371,9 +1372,16 @@ static void nvme_check_constraints(NvmeCtrl *n, Error 
**errp)
     }
 
     if (params->max_ioqpairs < 1 ||
-        params->max_ioqpairs > PCI_MSIX_FLAGS_QSIZE) {
+        params->max_ioqpairs > NVME_MAX_IOQPAIRS) {
         error_setg(errp, "max_ioqpairs must be between 1 and %d",
-                   PCI_MSIX_FLAGS_QSIZE);
+                   NVME_MAX_IOQPAIRS);
+        return;
+    }
+
+    if (params->msix_qsize < 1 ||
+        params->msix_qsize > PCI_MSIX_FLAGS_QSIZE + 1) {
+        error_setg(errp, "msix_qsize must be between 1 and %d",
+                   PCI_MSIX_FLAGS_QSIZE + 1);
         return;
     }
 
@@ -1527,7 +1535,7 @@ static void nvme_init_pci(NvmeCtrl *n, PCIDevice *pci_dev)
                           n->reg_size);
     pci_register_bar(pci_dev, 0, PCI_BASE_ADDRESS_SPACE_MEMORY |
                      PCI_BASE_ADDRESS_MEM_TYPE_64, &n->iomem);
-    msix_init_exclusive_bar(pci_dev, n->params.max_ioqpairs + 1, 4, NULL);
+    msix_init_exclusive_bar(pci_dev, n->params.msix_qsize, 4, NULL);
 
     if (n->params.cmb_size_mb) {
         nvme_init_cmb(n, pci_dev);
@@ -1634,6 +1642,7 @@ static Property nvme_props[] = {
     DEFINE_PROP_UINT32("cmb_size_mb", NvmeCtrl, params.cmb_size_mb, 0),
     DEFINE_PROP_UINT32("num_queues", NvmeCtrl, params.num_queues, 0),
     DEFINE_PROP_UINT32("max_ioqpairs", NvmeCtrl, params.max_ioqpairs, 64),
+    DEFINE_PROP_UINT16("msix_qsize", NvmeCtrl, params.msix_qsize, 65),
     DEFINE_PROP_END_OF_LIST(),
 };
 
diff --git a/hw/block/nvme.h b/hw/block/nvme.h
index 61dd9b23b81d..1d30c0bca283 100644
--- a/hw/block/nvme.h
+++ b/hw/block/nvme.h
@@ -7,6 +7,7 @@ typedef struct NvmeParams {
     char     *serial;
     uint32_t num_queues; /* deprecated since 5.1 */
     uint32_t max_ioqpairs;
+    uint16_t msix_qsize;
     uint32_t cmb_size_mb;
 } NvmeParams;
 
-- 
2.27.0