Am 08.01.2019 um 15:20 hat Paul Durrant geschrieben: > > -----Original Message----- > > From: Xen-devel [mailto:[email protected]] On Behalf > > Of Paul Durrant > > Sent: 08 January 2019 14:11 > > To: Anthony Perard <[email protected]> > > Cc: 'Kevin Wolf' <[email protected]>; Stefano Stabellini > > <[email protected]>; [email protected]; [email protected]; > > Max Reitz <[email protected]>; [email protected] > > Subject: Re: [Xen-devel] [PATCH v7 16/18] xen: automatically create > > XenBlockDevice-s > > > > > -----Original Message----- > > > From: Anthony PERARD [mailto:[email protected]] > > > Sent: 08 January 2019 13:28 > > > To: Paul Durrant <[email protected]> > > > Cc: 'Kevin Wolf' <[email protected]>; [email protected]; qemu- > > > [email protected]; [email protected]; Max Reitz > > > <[email protected]>; Stefano Stabellini <[email protected]> > > > Subject: Re: [PATCH v7 16/18] xen: automatically create XenBlockDevice-s > > > > > > On Tue, Jan 08, 2019 at 01:07:49PM +0000, Paul Durrant wrote: > > > > > -----Original Message----- > > > > > From: Kevin Wolf [mailto:[email protected]] > > > > > Sent: 08 January 2019 12:53 > > > > > To: Paul Durrant <[email protected]> > > > > > Cc: Anthony Perard <[email protected]>; qemu- > > [email protected]; > > > > > [email protected]; [email protected]; Max Reitz > > > > > <[email protected]>; Stefano Stabellini <[email protected]> > > > > > Subject: Re: [PATCH v7 16/18] xen: automatically create > > > XenBlockDevice-s > > > > > > > > > > Am 04.01.2019 um 17:40 hat Paul Durrant geschrieben: > > > > > > > -----Original Message----- > > > > > > > From: Anthony PERARD [mailto:[email protected]] > > > > > > > Sent: 04 January 2019 16:31 > > > > > > > To: Paul Durrant <[email protected]> > > > > > > > Cc: [email protected]; [email protected]; xen- > > > > > > > [email protected]; Kevin Wolf <[email protected]>; Max > > > Reitz > > > > > > > <[email protected]>; Stefano Stabellini <[email protected]> > > > > > > > Subject: Re: [PATCH v7 16/18] xen: automatically create > > > > > XenBlockDevice-s > > > > > > > > > > > > > > Almost done, there is one thing left which I believe is an > > issue. > > > > > > > Whenever I attach a raw file to QEMU, it print: > > > > > > > qemu-system-i386: warning: Opening a block device as a file > > > using > > > > > the > > > > > > > 'file' driver is deprecated > > > > > > > > > > > > Oh, I'd not noticed that... but then I only use raw files > > > occasionally. > > > > > > > > > > Strictly speaking, this is not about raw (regular) files, but raw > > > block > > > > > devices. 'file' is fine for actual regular files, but the protocol > > > > > driver for block devices is 'host_device'. > > > > > > > > > > > > raw files should use the "raw" driver, so we aren't done yet. > > > > > > > > > > > > Ok. Having a strictly 2-layer stack actually makes things simpler > > > anyway > > > > > :-) > > > > > > > > > > Using 'raw' there will make the block layer auto-detect the right > > > > > protocol layer, so this works. If you want to avoid the second > > layer, > > > > > you'd have to figure out manually whether to use 'file' or > > > > > 'host_device'. > > > > > > > > Thanks for the explanation. I'll give it a spin using a device... I've > > > posted v8 but, given what you say, I'm still not sure I have it right. > > > > > > Indeed, in v8, even with the extra 'raw' layer, the warning is still > > > there. I was trying to understand why, and I only found out today that > > > we would need to use the 'host_device' driver as explain by Kevin. > > > > > > > > > BTW Paul, we can simplify the code that manage layers, by not managing > > > them. > > > Instead of (in JSON / QMP term): > > > { 'driver': 'file', 'filename': '/file', 'node-name': 'node-file' } > > > { 'driver': 'qcow2', 'file': 'node-file', 'node-name': 'node-qcow2' > > } > > > we can have: > > > { 'driver': 'qcow2', 'node-name': 'node-qcow2', > > > 'file': { 'driver': 'file', 'filename': '/file' } } > > > > > > > I kind of like the clean separation though... From what Kevin said, it > > sounds like the lowest layer should use 'raw' instead of 'file' to DTRT, > > and then we should be back to only needing the single layer in that case. > > I'll revert back to v7 and give it a try. > > No, that doesn't work as we can't deal with locking correctly unless > we use driver=file so maybe I misunderstood.
The lowest layer should use 'host_device' there. 'raw' is the format layer that is stacked on top. I'm not sure what your locking requirements are, but 'host_device' supports the same options as 'file'. Kevin
