Re: [Qemu-devel] [PULL 13/76] pvh: Add x86/HVM direct boot ABI header file

[Alex Bennée]

Stefano Garzarella <address@hidden> writes:

> On Fri, Mar 01, 2019 at 04:53:57PM +0000, Alex Bennée wrote:
>>
>> Paolo Bonzini <address@hidden> writes:
>>
>> > From: Liam Merwick <address@hidden>
>> >
>> > The x86/HVM direct boot ABI permits Qemu to be able to boot directly
>> > into the uncompressed Linux kernel binary with minimal firmware 
>> > involvement.
>> >
>> >    https://xenbits.xen.org/docs/unstable/misc/pvh.html
>> >
>> > This commit adds the header file that defines the start_info struct
>> > that needs to be populated in order to use this ABI.
>> >
>> > The canonical version of start_info.h is in the Xen codebase.
>> > (like QEMU, the Linux kernel uses a copy as well).
>> >
>> > Signed-off-by: Liam Merwick <address@hidden>
>> > Reviewed-by: Konrad Rzeszutek Wilk <address@hidden>
>> > Signed-off-by: Paolo Bonzini <address@hidden>
>>
>> This has changed behaviour of a boot. Previously:
>>
>>   qemu-system-i386 -serial mon:stdio -nographic -device \
>>      isa-debugcon,chardev=serial0 -kernel ./tests/hello
>>
>
> Hi Alex,
> is your image in multiboot format?

AFAICT yes, I'm not super familiar with x86 so I'm mostly cribbing from:

  https://github.com/doug65536/qemu-bmibug

> I sent a patch few weeks ago that fix the loading of multiboot images:
> https://www.mail-archive.com/address@hidden/msg596424.html

That certainly fixes things. Although I'm wondering if it's worth making
my test image PVH compatible anyway (if it's easy to do) as all I really
want to do is exercise the softmmu code. It might be simpler to use
paravirtualised serial ports rather than banging an IO port, IDK?

>
> Thanks,
> Stefano
>
>> would boot seabios which then loads the -kernel. Now we get:
>>
>>   qemu-system-i386: Error loading uncompressed kernel without PVH ELF Note
>>
>> I'm personally not overly concerned (and being able to boot directly
>> sounds like a win for my test case). However is this likely to break
>> anybodies existing workflow?
>>
>> Are there any examples of the minimum setup for a directly booted i386
>> kernel image anywhere?
>>
>> --
>> Alex Bennée
>>


--
Alex Bennée