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[Qemu-block] [PATCH v5 8/9] docs: Add section for NVMe VFIO driver

From: Fam Zheng
Subject: [Qemu-block] [PATCH v5 8/9] docs: Add section for NVMe VFIO driver
Date: Fri, 12 Jan 2018 16:55:54 +0800

Signed-off-by: Fam Zheng <address@hidden>
Message-Id: <address@hidden>
 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
address@hidden disk_images_nvme
address@hidden 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:
+# 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 
address@hidden example
+Alternative syntax using properties:
+qemu-system-x86_64 -drive 
address@hidden example
address@hidden:@var{bus}:@address@hidden is the NVMe controller's PCI device
+address on the host.
address@hidden is the NVMe namespace number, starting from 1.
 @node disk_image_locking
 @subsection Disk image file locking

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