Re: Hyper-V SSD passthrough fix backport

[Stephen Hemminger <stephen@networkplumber.org>]

On Wed, 29 Nov 2017 12:09:03 +0000
Sitsofe Wheeler <sitsofe@gmail.com> wrote:

> On 29 November 2017 at 10:40, Sitsofe Wheeler <sitsofe@gmail.com> wrote:
> > On 29 November 2017 at 08:11, Sitsofe Wheeler <sitsofe@gmail.com> wrote:  
> >> On 29 November 2017 at 08:06, Greg KH <greg@kroah.com> 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.