Re: [Xen-devel] [RFC] xen/pvh: detect PVH after kexec

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 21.03.17 at 11:01, <roger.pau@xxxxxxxxxx> wrote:
> On Tue, Mar 21, 2017 at 10:21:52AM +0100, Vitaly Kuznetsov wrote:
>> Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> writes:
>> 
>> > On 03/20/2017 02:20 PM, Vitaly Kuznetsov wrote:
>> >> PVH guests after kexec boot like normal HVM guests and we're not entering
>> >> xen_prepare_pvh()
>> >
>> > Is it not? Aren't we going via xen_hvm_shutdown() and then
>> > SHUTDOWN_soft_reset which would restart at the same entry point as
>> > regular boot?
>> 
>> No, we're not doing regular boot: from outside of the guest we don't
>> really know where the new kernel is placed (as guest does it on its
>> own). We do soft reset to clean things up and then guest jumps to the
>> new kernel starting point by itself.
>> 
>> We could (in theory, didn't try) make it jump to the PVH starting point
>> but we'll have to at least prepare the right boot params for
>> init_pvh_bootparams and this looks like additional
>> complication. PVHVM-style startup suits us well but we still need to be
>> PVH-aware.
> 
> We are going to have the same issue when booting PVH with OVMF, Linux will be
> started at the native UEFI entry point, and we will need some way to detect
> that we are running in PVH mode.

I'm confused: PVH boots without any firmware, doesn't it? Hence
it shouldn't matter if there's no (legacy) BIOS or no OVMF ...

Jan


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