Re: [Xen-devel] Regression between Xen 4.6.0 and 4.7.0, Direct kernel boot on a qemu-xen and seabios HVM guest doesn't work anymore.

[linux@xxxxxxxxxxxxxx]

On 2016-08-25 23:18, linux@xxxxxxxxxxxxxx wrote:
> On 2016-08-25 22:34, Doug Goldstein wrote:
> > On 8/25/16 4:21 PM, linux@xxxxxxxxxxxxxx wrote:
> > > Today i tried to switch some of my HVM guests (qemu-xen) from booting 
> > > of
> > > a kernel *inside* the guest, to a dom0 supplied kernel, which is
> > > described as "Direct Kernel Boot" here:
> > > https://xenbits.xen.org/docs/unstable/man/xl.cfg.5.html :
> > >
> > >     Direct Kernel Boot
> > >
> > >     Direct kernel boot allows booting directly from a kernel and 
> > > initrd
> > > stored in the host physical
> > >     machine OS, allowing command line arguments to be passed 
> > > directly.
> > > PV guest direct kernel boot
> > >     is supported. HVM guest direct kernel boot is supported with
> > > limitation (it's supported when
> > >     using qemu-xen and default BIOS 'seabios'; not supported in case 
> > > of
> > > stubdom-dm and old rombios.)
> > >
> > >     kernel="PATHNAME"    Load the specified file as the kernel image.
> > >     ramdisk="PATHNAME"   Load the specified file as the ramdisk.
> > >
> > > But qemu fails to start, output appended below.
> > >
> > > I tested with:
> > > - current Xen-unstable, which fails.
> > > - xen-stable-4.7.0 release, which fails.
> > > - xen-stable-4.6.0 release, works fine.
> > Can you include the logs from xl dmesg around that time frame as well?
> Ah i thought there wasn't any, but didn't check thoroughly or wasn't 
> there
> since the release builds are non-debug by default.
>
> However, back on xen-unstable:
> (XEN) [2016-08-25 21:09:15.172] HVM19 save: CPU
> (XEN) [2016-08-25 21:09:15.172] HVM19 save: PIC
> (XEN) [2016-08-25 21:09:15.172] HVM19 save: IOAPIC
> (XEN) [2016-08-25 21:09:15.172] HVM19 save: LAPIC
> (XEN) [2016-08-25 21:09:15.172] HVM19 save: LAPIC_REGS
> (XEN) [2016-08-25 21:09:15.172] HVM19 save: PCI_IRQ
> (XEN) [2016-08-25 21:09:15.172] HVM19 save: ISA_IRQ
> (XEN) [2016-08-25 21:09:15.172] HVM19 save: PCI_LINK
> (XEN) [2016-08-25 21:09:15.172] HVM19 save: PIT
> (XEN) [2016-08-25 21:09:15.172] HVM19 save: RTC
> (XEN) [2016-08-25 21:09:15.172] HVM19 save: HPET
> (XEN) [2016-08-25 21:09:15.172] HVM19 save: PMTIMER
> (XEN) [2016-08-25 21:09:15.172] HVM19 save: MTRR
> (XEN) [2016-08-25 21:09:15.172] HVM19 save: VIRIDIAN_DOMAIN
> (XEN) [2016-08-25 21:09:15.172] HVM19 save: CPU_XSAVE
> (XEN) [2016-08-25 21:09:15.172] HVM19 save: VIRIDIAN_VCPU
> (XEN) [2016-08-25 21:09:15.172] HVM19 save: VMCE_VCPU
> (XEN) [2016-08-25 21:09:15.172] HVM19 save: TSC_ADJUST
> (XEN) [2016-08-25 21:09:15.172] HVM19 restore: CPU 0
> (XEN) [2016-08-25 21:09:16.126] d0v1 Over-allocation for domain 19:
> 262401 > 262400
> (XEN) [2016-08-25 21:09:16.126] memory.c:213:d0v1 Could not allocate
> order=0 extent: id=19 memflags=0 (192 of 512)
>
> Hmm some off by one issue ?
>
>
> > Just wondering how much RAM you're domain is defined with as well?
> 1024 Mb, there is more than enough unallocated memory for xen to start
> the guest (and dom0 is fixed with dom0_mem=1536M,max:1536M and
> ballooning is off)

Hmm it seems my thread was kind of hijacked and i was dropped from the 
CC.
I had some time and bisected the issue and it resulted in:

5a3ce8f85e7e7bdd339d259daa19f6bc5cb4735f is the first bad commit
commit 5a3ce8f85e7e7bdd339d259daa19f6bc5cb4735f
Author: Jan Beulich <jbeulich@xxxxxxxx>
Date:   Wed Oct 21 10:56:31 2015 +0200

    x86/shadow: drop stray name tags from sh_{guest_get,map}_eff_l1e()

    They (as a now being removed comment validly says) depend only on 
Xen's
    number of page table levels, and hence their tags didn't serve any
    useful purpose (there could only ever be one instance in a single
    binary, even back in the x86-32 days).

    Further conditionalize the inclusion of PV-specific hook pointers, 
at
    once making sure that PV guests can't ever get other than 4-level 
mode
    enabled for them.

    For consistency reasons shadow_{write,cmpxchg}_guest_entry() also 
get
    moved next to the other PV-only actors, allowing them to become 
static
    just like the $subject ones do.

    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Tim Deegan <tim@xxxxxxx>

:040000 040000 0c2e3475f81547f934a5960d9f1ac4849707d4ed 
f17f5ff17ca50d6ab908afe9a2d8555d954d3d0a M  xen

--
Sander


> --
> Sander
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