Re: [Xen-devel] kdump with xen-unstable on efi machine

[Daniel Kiper <daniel.kiper@xxxxxxxxxx>]

On Wed, Nov 26, 2014 at 03:49:54PM +0100, Juergen Gross wrote:
> On 11/26/2014 03:30 PM, Konrad Rzeszutek Wilk wrote:
> >On Wed, Nov 26, 2014 at 03:01:51PM +0100, Juergen Gross wrote:
> >>On 11/26/2014 01:41 PM, Andrew Cooper wrote:
> >>>On 26/11/14 12:15, Juergen Gross wrote:
> >>>>Hi,
> >>>>
> >>>>I tried to enable kdump on my test-machine with actual xen-unstable
> >>>>booting via EFI.
> >>>>
> >>>>The kdump kernel is not being loaded.
> >>>>
> >>>>I'm seeing the memory being reserved:
> >>>>
> >>>>(XEN) EFI RAM map:
> >>>>(XEN)  0000000000000000 - 00000000000a0000 (usable)
> >>>>(XEN)  0000000000100000 - 000000004bc00000 (usable)
> >>>>(XEN)  000000004bc00000 - 000000005bc00000 (reserved)
> >>>>(XEN)  000000005bc00000 - 000000005bfec000 (usable)
> >>>>(XEN)  000000005bfec000 - 000000005c000000 (ACPI NVS)
> >>>>(XEN)  000000005c000000 - 000000006a429000 (usable)
> >>>>(XEN)  000000006a429000 - 000000006a42c000 (reserved)
> >>>>(XEN)  000000006a42c000 - 000000006a7a2000 (usable)
> >>>>(XEN)  000000006a7a2000 - 000000006a7a8000 (reserved)
> >>>>(XEN)  000000006a7a8000 - 000000006a987000 (usable)
> >>>>(XEN)  000000006a987000 - 000000006a98d000 (reserved)
> >>>>(XEN)  000000006a98d000 - 000000006aa63000 (usable)
> >>>>(XEN)  000000006aa63000 - 000000006aa73000 (reserved)
> >>>>(XEN)  000000006aa73000 - 000000006ac60000 (usable)
> >>>>(XEN)  000000006ac60000 - 000000006ac61000 (reserved)
> >>>>(XEN)  000000006ac61000 - 000000006ac9b000 (ACPI data)
> >>>>(XEN)  000000006ac9b000 - 000000006acac000 (reserved)
> >>>>(XEN)  000000006acac000 - 000000006acad000 (usable)
> >>>>(XEN)  000000006acad000 - 000000006acae000 (reserved)
> >>>>(XEN)  000000006acae000 - 000000007189c000 (usable)
> >>>>(XEN)  000000007189c000 - 0000000071946000 (reserved)
> >>>>(XEN)  0000000071946000 - 0000000072d76000 (ACPI NVS)
> >>>>(XEN)  0000000072d76000 - 0000000072db2000 (ACPI data)
> >>>>(XEN)  0000000072db2000 - 0000000072edc000 (usable)
> >>>>(XEN)  0000000080000000 - 0000000090000000 (reserved)
> >>>>(XEN)  0000000100000000 - 0000002080000000 (usable)
> >>>>(XEN) Kdump: 256MB (262144kB) at 0x206dff4000
> >>>>
> >>>>I'd expect this area being visible in the efi or e820 map presented to
> >>>>dom0, but I can't see anything:
> >>>
> >>>This is expected.  The dom0 kernel now has nothing at all do with
> >>>loading crash kernel.  Loading happens via hypercalls straight from the
> >>>kexec utility.
> >>>
> >>>You need kexec-tools 2.0.4 (I think) or later, compiled with Xen
> >>>support, but it should JustWork.
> >>
> >>Should. I have kexec 2.0.5 with Xen support. Doesn't work:
> >>
> >>Excerpt form strace:
> >>
> >>"sysctl operation failed -- need to rebuild the user-space tool set?\n"
> >>
> >>My personal translation: kexec is tightly coupled to the Xen version
> >>(this one was built against Xen 4.4.1 AFAIK).
> >
> >Odd, the hypercall interface did not change in Xen 4.5 for kexec?
> >
> >Perhaps it is making some other hypercalls that are tied in
> >to the version of Xen (like sysctl ones?).
>
> The error message above suggests that, yes. :-)
>
> Grepping for xc_ in kexec sources finds e.g. xc_get_max_cpus() which
> in turn calls xc_physinfo() doing a sysctl.
>
> >
> >I presume with recompiling it works?
>
> Didn't check up to now, but I think it should.

Are you sure that kexec-tools configure script discovered
Xen headers and development libraries? Please check that.
"ldd kexec" is your friend.

Do not forget to use kexec-tools version 2.0.5 or newer.

> >>
> >>Perhaps we should add kexec to the tools directory?
> >
> >Gosh no.
>
> Oops, did I forget the smiley? ;-)
>
> I think we should look what kexec is really needing and put this in a
> stable interface set (perhaps an own library?). This might require some

David did the work.

> new sub functions of e.g. the KEXEC hypercall, but this is better than
> making kexec depending on the Xen version.

Maybe we need some things which are specific for EFI platforms. I am
going to investigate that after finishing EFI + multiboot2 work.
Probably it will happen at the beginning of next year.

Daniel

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