Signed-off-by: Fam Zheng <f...@redhat.com>
Message-Id: <20180110091846.10699-9-f...@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com>
---
docs/qemu-block-drivers.texi | 37 +++++++++++++++++++++++++++++++++++++
1 file changed, 37 insertions(+)
diff --git a/docs/qemu-block-drivers.texi b/docs/qemu-block-drivers.texi
index 503c1847aa..cd74767ed3 100644
--- a/docs/qemu-block-drivers.texi
+++ b/docs/qemu-block-drivers.texi
@@ -785,6 +785,43 @@ warning: ssh server @code{ssh.example.com:22} does not
support fsync
With sufficiently new versions of libssh2 and OpenSSH, @code{fsync} is
supported.
+@node disk_images_nvme
+@subsection NVMe disk images
+
+NVM Express (NVMe) storage controllers can be accessed directly by a userspace
+driver in QEMU. This bypasses the host kernel file system and block layers
+while retaining QEMU block layer functionalities, such as block jobs, I/O
+throttling, image formats, etc. Disk I/O performance is typically higher than
+with @code{-drive file=/dev/sda} using either thread pool or linux-aio.
+
+The controller will be exclusively used by the QEMU process once started. To be
+able to share storage between multiple VMs and other applications on the host,
+please use the file based protocols.
+
+Before starting QEMU, bind the host NVMe controller to the host vfio-pci
+driver. For example:
+
+@example
+# modprobe vfio-pci
+# lspci -n -s 0000:06:0d.0
+06:0d.0 0401: 1102:0002 (rev 08)
+# echo 0000:06:0d.0 > /sys/bus/pci/devices/0000:06:0d.0/driver/unbind
+# echo 1102 0002 > /sys/bus/pci/drivers/vfio-pci/new_id
+
+# qemu-system-x86_64 -drive
file=nvme://@var{host}:@var{bus}:@var{slot}.@var{func}/@var{namespace}
+@end example
+
+Alternative syntax using properties:
+
+@example
+qemu-system-x86_64 -drive
file.driver=nvme,file.device=@var{host}:@var{bus}:@var{slot}.@var{func},file.namespace=@var{namespace}
+@end example
+
+@var{host}:@var{bus}:@var{slot}.@var{func} is the NVMe controller's PCI device
+address on the host.
+
+@var{namespace} is the NVMe namespace number, starting from 1.
+
@node disk_image_locking
@subsection Disk image file locking
--
2.14.3
