From: David Vrabel <david.vrabel@citrix.com> To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: jgross@suse.com, Ian Jackson <Ian.Jackson@eu.citrix.com>, annie.li@oracle.com, xen-devel@lists.xen.org, Paul.Durrant@citrix.com, roger.pau@citrix.com Subject: Re: [RFC PATCH] blkif.h: document scsi/0x12/0x83 node Date: Tue, 22 Mar 2016 14:38:23 +0000 [thread overview] Message-ID: <56F158DF.3030002@citrix.com> (raw) In-Reply-To: <20160322141006.GA26390@char.us.oracle.com> 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). David _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
next prev parent reply other threads:[~2016-03-22 14:38 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 [this message] 2016-03-22 14:43 ` Paul Durrant 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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