[RFC PATCH 4/5] nvme-vfio: check if the hardware supports live migration

[Lei Rao]

NVMe device can extend the vendor-specific field in the identify
controller data structure to indicate whether live migration
is supported. This patch checks if the NVMe device supports
live migration.

Signed-off-by: Lei Rao <lei.rao@xxxxxxxxx>
Signed-off-by: Yadong Li <yadong.li@xxxxxxxxx>
Signed-off-by: Chaitanya Kulkarni <kch@xxxxxxxxxx>
Reviewed-by: Eddie Dong <eddie.dong@xxxxxxxxx>
Reviewed-by: Hang Yuan <hang.yuan@xxxxxxxxx>
---
 drivers/vfio/pci/nvme/nvme.c | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/drivers/vfio/pci/nvme/nvme.c b/drivers/vfio/pci/nvme/nvme.c
index 698e470a4e53..2ffc90ad556d 100644
--- a/drivers/vfio/pci/nvme/nvme.c
+++ b/drivers/vfio/pci/nvme/nvme.c
@@ -473,6 +473,36 @@ static void nvmevf_pci_close_device(struct vfio_device *core_vdev)
 	vfio_pci_core_close_device(core_vdev);
 }
 
+static bool nvmevf_check_migration(struct pci_dev *pdev)
+{
+	struct nvme_command c = { };
+	struct nvme_id_ctrl *id;
+	u8 live_mig_support;
+	int ret;
+
+	c.identify.opcode = nvme_admin_identify;
+	c.identify.cns = NVME_ID_CNS_CTRL;
+
+	id = kmalloc(sizeof(struct nvme_id_ctrl), GFP_KERNEL);
+	if (!id)
+		return false;
+
+	ret = nvme_submit_vf_cmd(pdev, &c, NULL, id, sizeof(struct nvme_id_ctrl));
+	if (ret) {
+		dev_warn(&pdev->dev, "Get identify ctrl failed (ret=0x%x)\n", ret);
+		goto out;
+	}
+
+	live_mig_support = id->vs[0];
+	if (live_mig_support) {
+		kfree(id);
+		return true;
+	}
+out:
+	kfree(id);
+	return false;
+}
+
 static const struct vfio_migration_ops nvmevf_pci_mig_ops = {
 	.migration_set_state = nvmevf_pci_set_device_state,
 	.migration_get_state = nvmevf_pci_get_device_state,
@@ -489,6 +519,10 @@ static int nvmevf_migration_init_dev(struct vfio_device *core_vdev)
 	if (!pdev->is_virtfn)
 		return ret;
 
+	/* Get the identify controller data structure to check the live migration support */
+	if (!nvmevf_check_migration(pdev))
+		return ret;
+
 	nvmevf_dev->migrate_cap = 1;
 
 	vf_id = pci_iov_vf_id(pdev);
-- 
2.34.1