Re: [Xen-devel] Xen 4.1 maintenance? (Was Re: [xen-4.1.6.1] SIGSEGV libxc/xc_save_domain.c: p2m_size >> configured_ram_size)

[Stefan Bader <stefan.bader@xxxxxxxxxxxxx>]

On 17.06.2016 11:31, George Dunlap wrote:
> On 13/06/16 12:14, Philipp Hahn wrote:
>> Am 13.06.2016 um 12:15 schrieb George Dunlap:
>>> On Fri, Jun 10, 2016 at 4:22 PM, Philipp Hahn <hahn@xxxxxxxxxxxxx> wrote:
>>>> while trying to live migrate some VMs from an xen-4.1.6.1 host "xc_save"
>>>> crashes with a segmentation fault in tools/libxc/xc_domain_save.c:1141
>>>>>         /*
>>>>>          * Quick belt and braces sanity check.
>>>>>          */
>>>>>         for ( i = 0; i < dinfo->p2m_size; i++ )
>>>>>         {
>>>>>             mfn = pfn_to_mfn(i);
>>>>>             if( (mfn != INVALID_P2M_ENTRY) && (mfn_to_pfn(mfn) != i) )
>>>>                                                  ^^^^^^^^^^^^^^^
>>>> due to a de-reference through
>>>>> #define pfn_to_mfn(_pfn)                                            \
>>>>>   ((xen_pfn_t) ((dinfo->guest_width==8)                               \
>>>>>                 ? (((uint64_t *)ctx->live_p2m)[(_pfn)])                  \
>>>>>                 : ((((uint32_t *)ctx->live_p2m)[(_pfn)]) == 0xffffffffU  \
>>>>>                    ? (-1UL) : (((uint32_t *)ctx->live_p2m)[(_pfn)]))))
>> ...
>>> Given that 4.1 is long out of support, we won't be making a proper fix
>>> in-tree (since it will never be released).
>>
>> I know that 4.1 is EOL.
>> I'm aware of Ubuntu still having xen-4.1 in one of their LTS versions
>> (Precise) and its also in Debian-oldstable, which a lot people (us
>> included) still use. I would prefer to update, but I can for reasons
>> outside my direct control.
>>
>> I'm already working with Stefan Bader from Canonical to backport most of
>> the XSAs to 4.1, so there already exists a "better" version outside of
>> the official Xen repositories.
> 
> Philipp / Stefan -- if there really is a large following of people still
> using 4.1, would it make sense to have one or both of you step up and
> maintain an official branch on xenbits?

Hi George,

[sorry for the late answer, I was busy/on vacation the last two weeks]

I can only speak for myself. So for me 4,1 will be relevant only until April
next year. So not a full year anymore. Also my take would be that if taking up
an official stable branch it should be done properly which takes time. And the
pool of spare time is rather dry these days. So I'd rather decline the honour.

Though one thing to improve as a compromise would be to do a better job of
submitting hard(er) backports more consistently to xen-devel for review (usually
I am doing my batches after lifting embargoes anyway).

-Stefan
> 
>  -George
>

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