[PATCH] hw/nvme: Add options to override hardcoded values

[Mauricio Sandt <mauricio@mailbox.org>]

This small patch is the result of some recent malware research I did
in a QEMU VM. The malware used multiple ways of querying info from
the VM disk and I needed a clean way to change those values from the
hypervisor.

I believe this functionality could be useful to more people from multiple
fields, sometimes you just want to change some default values and having
them hardcoded in the sourcecode makes that much harder.

This patch adds three config parameters to the nvme device, all of them
are optional to not break anything. If any of them are not specified,
the previous (before this patch) default is used.

-model - This takes a string and sets it as the devices model name.
If you don't specify this parameter, the default is "QEMU NVMe Ctrl".

-firmware - The firmware version string, max 8 ascii characters.
The default is whatever `QEMU_VERSION` evaluates to.

-nqn_override - Allows to set a custom nqn on the nvme device.
Only used if there is no subsystem. This string should be in the same
format as the default "nqn.2019-08.org.qemu:...", but there is no
validation for that. Its up to the user to provide a valid string.

Signed-off-by: Mauricio Sandt <mauricio@mailbox.org>
---
 hw/nvme/ctrl.c | 16 +++++++++++++---
 hw/nvme/nvme.h |  3 +++
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/hw/nvme/ctrl.c b/hw/nvme/ctrl.c
index 1e6e0fcad9..0e67217a63 100644
--- a/hw/nvme/ctrl.c
+++ b/hw/nvme/ctrl.c
@@ -6697,8 +6697,13 @@ static void nvme_init_subnqn(NvmeCtrl *n)
     NvmeIdCtrl *id = &n->id_ctrl;
 
     if (!subsys) {
-        snprintf((char *)id->subnqn, sizeof(id->subnqn),
+        if (n->params.nqn_override) {
+            snprintf((char *)id->subnqn, sizeof(id->subnqn),
+                 "%s", n->params.nqn_override);
+        } else {
+            snprintf((char *)id->subnqn, sizeof(id->subnqn),
                  "nqn.2019-08.org.qemu:%s", n->params.serial);
+        }
     } else {
         pstrcpy((char *)id->subnqn, sizeof(id->subnqn), (char*)subsys->subnqn);
     }
@@ -6712,8 +6717,10 @@ static void nvme_init_ctrl(NvmeCtrl *n, PCIDevice *pci_dev)
 
     id->vid = cpu_to_le16(pci_get_word(pci_conf + PCI_VENDOR_ID));
     id->ssvid = cpu_to_le16(pci_get_word(pci_conf + PCI_SUBSYSTEM_VENDOR_ID));
-    strpadcpy((char *)id->mn, sizeof(id->mn), "QEMU NVMe Ctrl", ' ');
-    strpadcpy((char *)id->fr, sizeof(id->fr), QEMU_VERSION, ' ');
+    strpadcpy((char *)id->mn, sizeof(id->mn),
+            n->params.model ? n->params.model : "QEMU NVMe Ctrl", ' ');
+    strpadcpy((char *)id->fr, sizeof(id->fr),
+            n->params.firmware ? n->params.firmware : QEMU_VERSION, ' ');
     strpadcpy((char *)id->sn, sizeof(id->sn), n->params.serial, ' ');
 
     id->cntlid = cpu_to_le16(n->cntlid);
@@ -6913,6 +6920,9 @@ static Property nvme_props[] = {
     DEFINE_PROP_LINK("subsys", NvmeCtrl, subsys, TYPE_NVME_SUBSYS,
                      NvmeSubsystem *),
     DEFINE_PROP_STRING("serial", NvmeCtrl, params.serial),
+    DEFINE_PROP_STRING("model", NvmeCtrl, params.model),
+    DEFINE_PROP_STRING("nqn_override", NvmeCtrl, params.nqn_override),
+    DEFINE_PROP_STRING("firmware", NvmeCtrl, params.firmware),
     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),
diff --git a/hw/nvme/nvme.h b/hw/nvme/nvme.h
index e41771604f..45bcf3e02e 100644
--- a/hw/nvme/nvme.h
+++ b/hw/nvme/nvme.h
@@ -394,6 +394,9 @@ typedef struct NvmeCQueue {
 
 typedef struct NvmeParams {
     char     *serial;
+    char     *model;
+    char     *firmware;
+    char     *nqn_override;
     uint32_t num_queues; /* deprecated since 5.1 */
     uint32_t max_ioqpairs;
     uint16_t msix_qsize;
-- 
2.25.1