From: Paul Durrant <Paul.Durrant@citrix.com> To: David Vrabel <email@example.com>, Konrad Rzeszutek Wilk <firstname.lastname@example.org> Cc: "email@example.com" <firstname.lastname@example.org>, "email@example.com" <firstname.lastname@example.org>, "email@example.com" <firstname.lastname@example.org>, Ian Jackson <Ian.Jackson@citrix.com>, Roger Pau Monne <email@example.com> Subject: Re: [RFC PATCH] blkif.h: document scsi/0x12/0x83 node Date: Tue, 22 Mar 2016 14:43:50 +0000 [thread overview] Message-ID: <4b73a1be8ee241c49b901902aa07e189@AMSPEX02CL03.citrite.net> (raw) In-Reply-To: <56F158DF.firstname.lastname@example.org> > -----Original Message----- > From: David Vrabel [mailto:email@example.com] > Sent: 22 March 2016 14:38 > To: Konrad Rzeszutek Wilk > Cc: Bob Liu; Ian Jackson; firstname.lastname@example.org; email@example.com; > firstname.lastname@example.org; Paul Durrant; Roger Pau Monne > Subject: Re: [Xen-devel] [RFC PATCH] blkif.h: document scsi/0x12/0x83 node > > On 22/03/16 14:10, Konrad Rzeszutek Wilk wrote: > > On Tue, Mar 22, 2016 at 01:41:43PM +0000, David Vrabel wrote: > >> On 22/03/16 12:55, Bob Liu wrote: > >>> > >>> On 03/17/2016 07:12 PM, Ian Jackson wrote: > >>>> David Vrabel writes ("Re: [Xen-devel] [RFC PATCH] blkif.h: document > scsi/0x12/0x83 node"): > >>>>> On 16/03/16 13:59, Bob Liu wrote: > >>>>>> But we'd like to get the VPD information(of underlying storage > device) also in Linux blkfront, even blkfront is not a SCSI device. > >>>>> > >>>>> Why does blkback/blkfront need to involved here? This is just some > >>>>> xenstore keys that can be written by the toolstack and directly read > by > >>>>> the relevant application in the guest. > >>>> > >>> > >>> They want a more generic way because the application may run on all > kinds of environment including baremetal. > >>> So they prefers to just call ioctl(SG_IO) against a storage device. > >>> > >>>> I'm getting rather a different picture here than at first. Previously > >>>> I thought you had some 3rd-party application, not under your control, > >>>> which expected to see this VPD data. > >>>> > >>>> But now I think that you're saying the application is under your own > >>>> control. I don't understand why synthetic VPD data is the best way to > >>>> give your application the information it needs. > >>>> > >>>> What is the application doing with this VPD data ? I mean, > >>>> which specific application functions, and how do they depend on the > >>>> VPD data ? > >>>> > >>> > >>> From the feedbacks I just got, they do *not* want the details to be in > public. > >> > >> It is difficult to suggest how it should be done correctly without this > >> information. > > > > Just think of it as a black box. > > This isn't sufficient. > > You are presenting a solution but have not properly described the > problem so no one can evaluate whether the solution is appropriate. > > >> I also find it difficult to see a use case where running the storage > >> software in the guest (instead of in the backend) is sensible or desirable. > > > > Are you suggesting that doing backend drivers is not sensible? > > I do not understand your question. > > >>> Anyway, I think this is not a block of this patch. > >>> In Windows PV block driver, we already use the same way to get the raw > INQUIRY data. > >>> * The Windows PV block driver accepts ioctl(SG_IO). > >>> * Then it reads this /scsi/0x12/0x83 node. > >>> * Then return the raw INQURIY data back to ioctl. > >>> > >>> Since Linux guest also wants to do the same thing, let's making this > mechanism to be a generic interface! > >>> I'll post a patch adding ioctl(SG_IO) support to xen-blkfront together > with a updated version of this patch soon. > >> > >> I do not think this feature is generally useful outside of this > >> unspecified use case. I do not think that supplying details about > >> underlying storage device (beyond generic properties) to guests is > >> sensible (e.g., what if the guest snapshot is restored on different > >> storage?). > > > > The restore process (xl) can update the XenStore key with the new > storage. > > And how is this going to be communicated to the application using the data? > > >> And thus I do not not think we should either: a) make this part of the > >> blkif ABI; or b) add support to xen-blkfront or xen-blkback. > > > > It is already coded in Windows PV drivers so I am not following why > > codyfing this in the blkif.h is harmful? > > My understanding was that this was a legacy hack that should be removed > (we do not currently make use of it). > AFAIK XenServer still very much makes use of it. Paul > David _______________________________________________ Xen-devel mailing list Xenemail@example.com http://lists.xen.org/xen-devel
next prev parent reply other threads:[~2016-03-22 14:43 UTC|newest] Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-03-16 3:09 Bob Liu 2016-03-16 7:16 ` Konrad Rzeszutek Wilk 2016-03-16 12:36 ` Ian Jackson 2016-03-16 13:59 ` Bob Liu 2016-03-16 14:07 ` Paul Durrant 2016-03-17 5:04 ` Bob Liu 2016-03-16 14:32 ` David Vrabel 2016-03-17 5:07 ` Bob Liu 2016-03-17 11:12 ` Ian Jackson 2016-03-17 11:18 ` David Vrabel 2016-03-17 11:20 ` Ian Jackson 2016-03-22 12:55 ` Bob Liu 2016-03-22 13:41 ` David Vrabel 2016-03-22 14:10 ` Konrad Rzeszutek Wilk 2016-03-22 14:38 ` David Vrabel 2016-03-22 14:43 ` Paul Durrant [this message] 2016-03-22 15:09 ` Ian Jackson 2016-03-22 15:25 ` Paul Durrant 2016-03-22 16:14 ` Ian Jackson 2016-03-22 16:50 ` Konrad Rzeszutek Wilk 2016-03-22 17:39 ` Paul Durrant 2016-03-22 15:12 ` Ian Jackson 2016-03-22 15:27 ` Konrad Rzeszutek Wilk 2016-03-22 16:11 ` Ian Jackson 2016-03-22 16:38 ` Konrad Rzeszutek Wilk 2016-03-22 16:25 ` Jan Beulich 2016-03-16 14:33 ` Ian Jackson
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