Re: [Xen-devel] [PATCH v8 05/32] libxc: introduce a domain loader for HVM guest firmware

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 08/10/15 12:04, Ian Campbell wrote:
> On Thu, 2015-10-08 at 12:43 +0200, Roger Pau Monnà wrote:
>>> However I'm unsure that the presence or absence of ELF notes is sufficient,
>>> since there is at least the legacy SHT_NOTE section and then __xen_guest
>>> section (see the tail of elf_xen_parse) as well.
>> AFAICT NetBSD still uses the __xen_guest section, and it works fine with
>> this change:
>>
>> http://cvsweb.netbsd.org/bsdweb.cgi/~checkout~/src/sys/arch/amd64/amd64/locore.S?rev=1.78&content-type=text/plain&only_with_tag=MAIN
>>
>> elfloader recognizes the kernel and it's able to load it without issues.
>>
>> xc_dom_parse_elf_kernel already calls elf_xen_parse later on, while
>> trying to load the kernel, so the functionality it's exactly the same,
>> it's just that we now simply refuse to try to load a kernel without
>> elfnotes with elfloader.
>>
>> Without this change the elfloader would try to load a kernel without
>> elfnotes just to fail later while parsing it.
> Great, thanks for confirming.
>
>>> It's a bit of a shame to now have to parse the ELF twice. How abusive would
>>> to be to declare that when a xc_dom ->probe hook returns success it is
>>> entitled to rely on the contents of dom->loader_private being preserved
>>> until ->parse is called. In turn this would imply that the first successful
>>> probe would be used rather than e.g. probing everything and then picking a
>>> winner from the successful applicants.
>> We already do this, we stop testing once a probe returns 0 (see
>> xc_dom_find_loader), and use that as the loader, so there's no
>> functional change in this aspect. IMHO, this approach is not very
>> intrusive, would you like me implement it in a followup patch or rather
>> do it in the series?
> I think this series is big enough that we need to start draining the
> pipeline. So lets address this later.
>
> On the basis that v7 was Reviewed by Andy and Acked by Wei and that I've
> looked at the delta (only) from that:
>
> Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

v8 also Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

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