[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH RESEND] tools/libxl: add support for emulated NVMe drives
On Wed, Jan 18, 2017 at 10:51:50AM +0000, Paul Durrant wrote: > > -----Original Message----- > > From: Wei Liu [mailto:wei.liu2@xxxxxxxxxx] > > Sent: 18 January 2017 10:29 > > To: Paul Durrant <Paul.Durrant@xxxxxxxxxx> > > Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx; Ian Jackson <Ian.Jackson@xxxxxxxxxx>; > > Wei Liu <wei.liu2@xxxxxxxxxx> > > Subject: Re: [PATCH RESEND] tools/libxl: add support for emulated NVMe > > drives > > > > On Fri, Jan 13, 2017 at 02:00:41PM +0000, Paul Durrant wrote: > > > Upstream QEMU supports emulation of NVM Express a.k.a. NVMe drives. > > > > > > This patch adds a new vdev type into libxl to allow such drives to be > > > presented to HVM guests. Because the purpose of the new vdev is purely > > > to configure emulation, the syntax only supports specification of > > > whole disks. Also there is no need to introduce a new concrete VBD > > > encoding for NVMe drives. > > > > This seems to be in contradiction with the code below? > > > > No, there's no contradiction because the encoding is identical to xvdX > encoding. Perhaps I should state that in the comment. > That would be appreciated. > > > > > > NOTE: QEMU's emulation only supports a single NVMe namespace, so the > > > vdev syntax does not include specification of a namespace. > > > Also, current versions of SeaBIOS do not support booting from > > > NVMe devices, so the vdev should only be used for secondary > > > drives. > > > > > > > I don't know much about NVMe, but I presume we could just extend the > > proposed syntax to support namespaces should the need arise? > > > > Well, I could make the syntax be nvme<device>n<namespace> (to match linux's > namespace syntax) and insist that namespace be 1 at the moment. Do you think > that would be preferable? > Fine by me. Let's wait a bit for other people to comment. > > > Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx> > > > --- > > > Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx> > > > Cc: Wei Liu <wei.liu2@xxxxxxxxxx> > > > --- > > > docs/man/xen-vbd-interface.markdown.7 | 15 ++++++++------- > > > docs/man/xl-disk-configuration.pod.5 | 4 ++-- > > > tools/libxl/libxl_device.c | 8 ++++++++ > > > tools/libxl/libxl_dm.c | 6 ++++++ > > > 4 files changed, 24 insertions(+), 9 deletions(-) > > > > > > diff --git a/docs/man/xen-vbd-interface.markdown.7 b/docs/man/xen- > > vbd-interface.markdown.7 > > > index 1c996bf..8fd378c 100644 > > > --- a/docs/man/xen-vbd-interface.markdown.7 > > > +++ b/docs/man/xen-vbd-interface.markdown.7 > > > @@ -8,12 +8,12 @@ emulated IDE, AHCI or SCSI disks. > > > The abstract interface involves specifying, for each block device: > > > > > > * Nominal disk type: Xen virtual disk (aka xvd*, the default); SCSI > > > - (sd*); IDE or AHCI (hd*). > > > + (sd*); IDE or AHCI (hd*); NVMe. > > > > NVMe (nvme*) ? > > Yes. > > > > > > > > > - For HVM guests, each whole-disk hd* and and sd* device is made > > > - available _both_ via emulated IDE resp. SCSI controller, _and_ as a > > > - Xen VBD. The HVM guest is entitled to assume that the IDE or SCSI > > > - disks available via the emulated IDE controller target the same > > > + For HVM guests, each whole-disk hd*, sd* or nvme* device is made > > > + available _both_ via emulated IDE, SCSI controller or NVMe drive > > > + respectively _and_ as a Xen VBD. The HVM guest is entitled to > > > + assume that the disks available via the emulation target the same > > > > How do you expect the guest to deal with multipath NVMe devices? Maybe > > we need to add unplug support for NVMe devices in QEMU? > > That's true. For convenience, there would need to a QEMU patch for unplug to > allow displacement of the emulated device with PV. I can document this as a > shortcoming at the moment, if that's ok? > The unplug functionality, as I understand, is crucial to data integrity. Documenting this as shortcoming doesn't seem to be good enough. Do we need to wait until QEMU is ready before we can apply this patch? Wei. > Paul _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx https://lists.xen.org/xen-devel
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