On Thu, 7 Dec 2017 07:10:45 +0000 Sitsofe Wheeler <sitsofe@xxxxxxxxx> wrote: > (Forwarding to all Hyper-V maintainers due to lack of response to > Greg's question. > > There's something about this patch which makes it keep falling through > the cracks: in March when someone asked for this patch to be > backported (http://lkml.iu.edu/hypermail/linux/kernel/1703.3/03056.html > ) no one confirmed it should so Greg wound up dropping it > (http://lkml.iu.edu/hypermail/linux/kernel/1703.3/04774.html ). Given > this, can I urge people not to overlook this latest query...) > > ---------- Forwarded message ---------- > From: Greg KH <greg@xxxxxxxxx> > Date: 4 December 2017 at 12:10 > Subject: Re: Hyper-V SSD passthrough fix backport > To: Stephen Hemminger <stephen@xxxxxxxxxxxxxxxxxx> > Cc: Sitsofe Wheeler <sitsofe@xxxxxxxxx>, stable > <stable@xxxxxxxxxxxxxxx>, "Martin K. Petersen" > <martin.petersen@xxxxxxxxxx> > > > On Wed, Nov 29, 2017 at 03:21:08PM -0800, Stephen Hemminger wrote: > > On Wed, 29 Nov 2017 12:09:03 +0000 > > Sitsofe Wheeler <sitsofe@xxxxxxxxx> wrote: > > > > > On 29 November 2017 at 10:40, Sitsofe Wheeler <sitsofe@xxxxxxxxx> wrote: > > > > On 29 November 2017 at 08:11, Sitsofe Wheeler <sitsofe@xxxxxxxxx> wrote: > > > >> On 29 November 2017 at 08:06, Greg KH <greg@xxxxxxxxx> wrote: > > > >>> On Tue, Nov 28, 2017 at 10:58:25PM +0000, Sitsofe Wheeler wrote: > > > >>>> I'd like to nominate f1c635b439a5c01776fe3a25b1e2dc546ea82e6f > > > >>>> (https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/scsi/storvsc_drv.c?id=f1c635b439a5c01776fe3a25b1e2dc546ea82e6f > > > >>>> ) to be backported to 4.4 stable because it looks like without it > > > >>>> passthrough SSD disks won't work and will generate faux devices. It is > > > >>>> also being carried by Ubuntu: > > > >>>> http://kernel.ubuntu.com/git/ubuntu/ubuntu-xenial.git/log/drivers/scsi/storvsc_drv.c?h=Ubuntu-4.4.0-98.121 > > > >>>> along with other Hyper-V patches in their 4.4 tree. > > > >>>> > > > >>>> I'm not 100% sure that this one will fix what is being seen but I'm > > > >>>> coming to this conclusion based on > > > >>>> https://bugs.launchpad.net/ubuntu/xenial/+source/linux/+bug/1679898/comments/144 > > > >>> > > > >>> Can you test it to determine if this really does what you think it does > > > >>> to solve the problem? The changelog text makes it seem not necessary at > > > >>> all. > > > >> > > > >> I agree the changelog makes it seem totally unnecessary but the > > > >> changelog is wrong in this case :-) I have checked out 4.4.102 and > > > >> built it, run it and hit the error. When applying the patch attached > > > >> (which is basically f1c635b439a5c01776fe3a25b1e2dc546ea82e6f with the > > > >> lines removing static int msft_blist_flags = BLIST_TRY_VPD_PAGES; > > > >> moved about) and the problem was resolved. > > > >> > > > >> I'm happy for others to weigh on what I'm seeing. > > > > > > > > I will also note that this patch was deemed necessary/suitable for > > > > backporting to 4.9 and 4.10 back in May - > > > > (https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/log/drivers/scsi/storvsc_drv.c?h=linux-4.9.y > > > > and https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/log/drivers/scsi/storvsc_drv.c?h=linux-4.10.y > > > > ). Looking at https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/log/drivers/scsi/storvsc_drv.c?h=linux-4.1.y > > > > perhaps this is also suitable for 4.1 stable too (but I haven't tested > > > > 4.1, only 4.4.102)... > > > > > > One more data point - back in May > > > (https://www.spinics.net/lists/stable/msg170046.html ) you noted this > > > in relation to one of the stable patch requests for this: > > > "it's interesting how you deleted the changelog > > > comments here saying this was only needed for 4.11 and no older kernels > > > :)" > > > > > > and there's a follow up reply > > > (https://www.spinics.net/lists/stable/msg170125.html ) where Stephen > > > says: > > > > > > "At the time I only had reports of problem with 4.11. > > > But others ran into issue with 4.10 and 4.9" > > > > The changelog was about where the problem was seen. It makes sense > > that this also occurs with other classes of storage devices; > > hadn't tried all the possible configurations. > > So, what does the maintainer of the driver recommend here? Should I > backport this patch, or not? > > thanks, > > greg k-h > I was waiting for some feedback from Dexuan who has done most of the recent work on Hyper-V storage. His feedback is. > Hi Stephen, > My understanding is that the patch was made to work around a host emulation > defect of SCSI DVD device, so old kernels should also need this patch, but I didn't > know it could fix SSD passthrough, and actually I was not aware of any bug > related to SSD passthrough. > > Thanks, > -- Dexuan So yes, I think the backport is appropriate. The SSD fix is an added beneficial side effect.