> -----Original Message----- > From: Xen-devel [mailto:xen-devel-boun...@lists.xen.org] On Behalf Of > Paul Durrant > Sent: 22 March 2017 16:32 > To: Ian Jackson <ian.jack...@citrix.com> > Cc: xen-de...@lists.xenproject.org; Wei Liu <wei.l...@citrix.com> > Subject: Re: [Xen-devel] [PATCH RESEND] tools/libxl: add support for > emulated NVMe drives > > > -----Original Message----- > > From: Ian Jackson [mailto:ian.jack...@eu.citrix.com] > > Sent: 22 March 2017 16:03 > > To: Paul Durrant <paul.durr...@citrix.com> > > Cc: xen-de...@lists.xenproject.org; Wei Liu <wei.l...@citrix.com> > > Subject: RE: [PATCH RESEND] tools/libxl: add support for emulated NVMe > > drives > > > > Paul Durrant writes ("RE: [PATCH RESEND] tools/libxl: add support for > > emulated NVMe drives"): > > > > Oh, wait, I have just noticed that you have reused an entry in this > > > > table! > > > > > > > > 1 << 28 | disk << 8 | partition xvd, disks or partitions 16 > > > > onwards > > > > ... > > > > > + 1 << 28 | disk << 8 nvme, all disks, whole disk > > > > > only > > > > > > Yes, that was intentional. No need for a new concrete encoding if we > > > ignore namespaces, as I said in the commit comment. If you want to > > > support namespaces then it would need something new... which doesn't > > > seem worth it since QEMU has no support. > > > > That's not my point. The purpose of this table is to advise guests > > what the conventional in-guest device name ought to be for a certain > > vbd. > > Yes, and xvd<something> is a perfectly fine name for a PV device in pretty > much every case. It's already the case that emulated IDE disks are exposed to > guests using xvd* numbering. > > > > > We can't have one single numerical encoding mapping to two device > > names. That makes no sense. > > > > Presumably these NVME devices should be subject to the same vbd and > > unplug approach as scsi and ide disks. > > Yes, that's what the QEMU patch does. > > > In which case guests need to > > be told that the device name for the vbd should be "nvme<something>", > > which can only be done by using a different number. > > > > That means modifications to PV frontends would be needed, which is going > to make things more difficult. Most OS find disks by UUID these days anyway > so I'm still not sure that just using xvd* numbering would really be a > problem. >
Also, if we're going to go for distinct numbering then I guess the QEMU patch is probably wrong because we'd want guests with non-aware PV frontend to leave emulated NVMe devices plugged in. Paul > Paul > > > Ian. > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xen.org > https://lists.xen.org/xen-devel _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel
