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This BZ tracks the upstream work currently being done by Fam to introduce a VFIO based NVMe driver to QEMU:
https://lists.gnu.org/archive/html/qemu-devel/2016-12/msg02812.html
Date: Wed, 21 Dec 2016 00:31:35 +0800
From: Fam Zheng <famz>
Subject: [Qemu-devel] [PATCH 0/4] RFC: A VFIO based block driver for NVMe device
This series adds a new protocol driver that is intended to achieve about 20%
better performance for latency bound workloads (i.e. synchronous I/O) than
linux-aio when guest is exclusively accessing a NVMe device, by talking to the
device directly instead of through kernel file system layers and its NVMe
driver.
This applies on top of Stefan's block-next tree which has the busy polling
patches - the new driver also supports it.
A git branch is also available as:
https://github.com/famz/qemu nvme
See patch 4 for benchmark numbers.
Tests are done on QEMU's NVMe emulation and a real Intel P3700 SSD NVMe card.
Most of dd/fio/mkfs/kernel build and OS installation testings work well, but an
weird write fault looking similar to [1] is consistently seen when installing
RHEL 7.3 guest, which is still under investigation.
[1]: http://lists.infradead.org/pipermail/linux-nvme/2015-May/001840.html
Also, the ram notifier is not enough for hot plugged block device because in
that case the notifier is installed _after_ ram blocks are added so it won't
get the events.
(In reply to Miroslav Rezanina from comment #13)
> Fix included in qemu-kvm-rhev-2.12.0-4.el7
(workspace) [root@ibm-p8-garrison-03 vmt]# /usr/libexec/qemu-kvm --version
QEMU emulator version 2.12.0 (qemu-kvm-rhev-2.12.0-4.el7)
Copyright (c) 2003-2017 Fabrice Bellard and the QEMU Project developers
(workspace) [root@ibm-p8-garrison-03 vmt]# /usr/libexec/qemu-kvm -drive file=nvme://0001:01:00.0/1,if=none,id=drive0 -device virtio-blk,drive=drive0
qemu-kvm: -drive file=nvme://0001:01:00.0/1,if=none,id=drive0: VFIO IOMMU check failed
Still failed with latest qemu.
Tested nvme:// with basic block testing and block migration(drive mirror+nbd) testing.
NVMe SSD: Intel P3700
Know issue:
Bug 1587992 - nvme:// image creation support
Set this bug to 'VERIFIED'.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://access.redhat.com/errata/RHBA-2018:3443