Re: [REGRESSION] Linux 6.6.64 crashes when booting as PVH domU

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

On Wed, Dec 11, 2024 at 04:10:11PM +0100, Ard Biesheuvel wrote:
> On Wed, 11 Dec 2024 at 14:46, Greg Kroah-Hartman
> <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> >
> > On Wed, Dec 11, 2024 at 02:39:33PM +0100, Marek Marczykowski-Górecki wrote:
> > > On Wed, Dec 11, 2024 at 01:37:52PM +0100, Ard Biesheuvel wrote:
> > > > (cc Greg)
> > > >
> > > > On Wed, 11 Dec 2024 at 13:30, Marek Marczykowski-Górecki
> > > > <marmarek@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> > > > >
> > > > > On Wed, Dec 11, 2024 at 01:24:08PM +0100, Ard Biesheuvel wrote:
> > > > > > On Wed, 11 Dec 2024 at 12:53, Jürgen Groß <jgross@xxxxxxxx> wrote:
> > > > > > >
> > > > > > > Jason, Ard,
> > > > > > >
> > > > > > > I guess there are some prereq patches missing in stable 6.6.y 
> > > > > > > branch?
> > > > > > >
> > > > > > >
> > > > > > > Juergen
> > > > > > >
> > > > > > > On 11.12.24 12:41, Marek Marczykowski-Górecki wrote:
> > > > > > > > Hi,
> > > > > > > >
> > > > > > > > With Linux 6.6.64 I get the following crash on domU boot:
> > > > > > > >
> > > > > > > > (XEN) d5v0 Triple fault - invoking HVM shutdown action 1
> > > > > > > > (XEN) *** Dumping Dom5 vcpu#0 state: ***
> > > > > > > > (XEN) ----[ Xen-4.19.0  x86_64  debug=n  Tainted:  M     ]----
> > > > ...
> > > > > > > >
> > > > > > > > Linux 6.6.63 works fine.
> > > > > > > >
> > > > > > > > Looking at the changes, I suspect one of those:
> > > > > > > >
> > > > > > > >      83d123e27623 x86/pvh: Call C code via the kernel virtual 
> > > > > > > > mapping
> > > > > > > >      f662b4a69e1d x86/pvh: Set phys_base when calling 
> > > > > > > > xen_prepare_pvh()
> > > > > > > >
> > > > > >
> > > > > > The second patch shouldn't have been backported. It is unnecessary,
> > > > > > given that in the old situation, the kernel image needs to be loaded
> > > > > > at a fixed address. And it assumes  that %rbp is set to the physical
> > > > > > load offset, but those patches were not backported.
> > > > >
> > > > > It has this tag:
> > > > >
> > > > >     Stable-dep-of: e8fbc0d9cab6 ("x86/pvh: Call C code via the kernel 
> > > > > virtual mapping")
> > > > >
> > > >
> > > > That was added by the stable maintainers - someone grabbed a patch
> > > > from the middle of an unrelated series to make e8fbc0d9cab6 apply
> > > > without lexical conflicts.
> > > >
> > > > > Does it mean neither of them should be backported?
> > > > >
> > > > > But then, the e8fbc0d9cab6 has "Fixes:" tag (pointing at very old
> > > > > commit).
> > > > >
> > > >
> > > > If someone thinks e8fbc0d9cab6 should be backported, they should
> > > > rebase it onto v6.6.y, not backport random other patches until
> > > > git-apply stops complaining. And ideally, someone would build and boot
> > > > the result to check whether it works.
> > > >
> > > > For now, it would be better to revert both.
> > >
> > > I can confirm that reverting both commits fixes the issue.
> >
> > Ok, thanks, let me go rip all of these out and do a new release now to
> > fix the issue.  Sorry about that, and thanks so much for the testing and
> > letting us know!
> >
> 
> I guess 6.11 is beyond repair?

6.11.y is end-of-life for a week or so now, sorry.  Hopefully no one is
still using it (I did hear that Fedora is using it, so I don't know...)

greg k-h