Re: [PATCHv9 0/9] Xen: extend kexec hypercall for use with pv-ops kernels

[David Vrabel <david.vrabel@citrix.com>]

On 05/11/13 17:41, Daniel Kiper wrote:
> On Thu, Oct 31, 2013 at 11:21:48PM +0100, Daniel Kiper wrote:
>> On Thu, Oct 31, 2013 at 06:30:32PM +0000, David Vrabel wrote:
>>> On 31/10/2013 16:59, Don Slutz wrote:
> 
> [...]
> 
>>>> A possible fix is attached as (0002...) this does allow me to get into
>>>> the crash kernel.
>>>
>>> Thanks for tracking this down. This should be fixed in the tools by
>>> correctly aligning that segment.
> 
> With Don's patch (workaround) crash kernel works from time to time.
> I hope that proper fix will solve this issue.
> 
>> I have rebuild all binaries and results are the same. Configuration
>> changes does not help too. Don's patches solve some issues but dump
>> system still does not load (I use Linux Kernel 3.10.17). I can see
>> only following messages in all cases:
>>
>> I'm in purgatory
>> early console in decompress_kernel
> 
> It looks that early VGA code touches VGA memory buffer (0xb8000).
> When I mapped 0 - 1 MiB memory region (using machine_kexec_add_page()
> in xen/arch/x86/machine_kexec.c:machine_kexec_load() everything
> started working. So, sadly, I think we should map unconditionally
> this memory region too.

Thanks for tracking this down.

Mapping all of 0 - 1 MiB seems reasonable to me, but this should be done
by kexec-tools specifying this and not by Xen.

I'll post updated Xen and kexec-tools patches tomorrow hopefully.

David