Re: [Xen-devel] Linux 4.19.5 fails to boot as Xen dom0

[Greg KH <greg@xxxxxxxxx>]

On Thu, Dec 06, 2018 at 12:31:15PM +0100, Juergen Gross wrote:
> On 06/12/2018 12:13, Greg KH wrote:
> > On Thu, Nov 29, 2018 at 02:35:17PM +0100, Juergen Gross wrote:
> >> On 29/11/2018 14:26, Kirill A. Shutemov wrote:
> >>> On Thu, Nov 29, 2018 at 09:41:25AM +0000, Juergen Gross wrote:
> >>>> On 29/11/2018 02:22, Hans van Kranenburg wrote:
> >>>>> Hi,
> >>>>>
> >>>>> As also seen at:
> >>>>> https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=914951
> >>>>>
> >>>>> Attached there are two serial console output logs. One is starting with
> >>>>> Xen 4.11 (from debian unstable) as dom0, and the other one without Xen.
> >>>>>
> >>>>> [    2.085543] BUG: unable to handle kernel paging request at
> >>>>> ffff888d9fffc000
> >>>>> [    2.085610] PGD 200c067 P4D 200c067 PUD 0
> >>>>> [    2.085674] Oops: 0000 [#1] SMP NOPTI
> >>>>> [    2.085736] CPU: 1 PID: 1 Comm: swapper/0 Not tainted
> >>>>> 4.19.0-trunk-amd64 #1 Debian 4.19.5-1~exp1+pvh1
> >>>>> [    2.085823] Hardware name: HP ProLiant DL360 G7, BIOS P68 05/21/2018
> >>>>> [    2.085895] RIP: e030:ptdump_walk_pgd_level_core+0x1fd/0x490
> >>>>> [...]
> >>>>
> >>>> The offending stable commit is 4074ca7d8a1832921c865d250bbd08f3441b3657
> >>>> ("x86/mm: Move LDT remap out of KASLR region on 5-level paging"), this
> >>>> is commit d52888aa2753e3063a9d3a0c9f72f94aa9809c15 upstream.
> >>>>
> >>>> Current upstream kernel is booting fine under Xen, so in general the
> >>>> patch should be fine. Using an upstream kernel built from above commit
> >>>> (with the then needed Xen fixup patch 1457d8cf7664f34c4ba534) is fine,
> >>>> too.
> >>>>
> >>>> Kirill, are you aware of any prerequisite patch from 4.20 which could be
> >>>> missing in 4.19.5?
> >>>
> >>> I'm not.
> >>>
> >>> Let me look into this.
> >>>
> >>
> >> What is making me suspicious is the failure happening just after
> >> releasing the init memory. Maybe there is an access to .init.data
> >> segment or similar? The native kernel booting could be related to the
> >> usage of 2M mappings not being available in a PV-domain.
> > 
> > Did this ever get fixed anywhere that I can properly backport it to the
> > 4.19.y tree?
> 
> https://lore.kernel.org/lkml/20181130202328.65359-2-kirill.shutemov@xxxxxxxxxxxxxxx/
> 
> Still pending upstream. Just pinged tglx.

Thanks, it should have gotten a cc: stable@ tag, but I can watch out for
it...

greg k-h

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