linux-kernel - Re: [PATCH 0/3] x86/xen: support booting PVH guest via standard boot path

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Date:   Wed, 8 Nov 2017 08:47:54 -0500
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Juergen Gross <jgross@...e.com>, linux-kernel@...r.kernel.org,
        x86@...nel.org, kvm@...r.kernel.org, xen-devel@...ts.xenproject.org
Cc:     tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        pbonzini@...hat.com, rkrcmar@...hat.com, rjw@...ysocki.net,
        len.brown@...el.com, pavel@....cz
Subject: Re: [PATCH 0/3] x86/xen: support booting PVH guest via standard boot
 path

On 11/08/2017 08:40 AM, Juergen Gross wrote:
> On 08/11/17 14:37, Boris Ostrovsky wrote:
>> On 11/08/2017 04:07 AM, Juergen Gross wrote:
>>> Booting a Xen PVH guest requires a special boot entry as it is
>>> mandatory to setup some Xen-specific interfaces rather early. When grub
>>> or OVMF are used as boot loaders, however, those will fill the boot
>>> parameters in zeropage and there is no longer a need to do something
>>> PVH specific in the early boot path.
>>>
>>> This patch series adds support for that scenario by identifying PVH
>>> environment and doing the required init steps via Xen hooks instead of
>>> using a dedicated boot entry.
>>>
>>> The dedicated entry is still needed for support of Dom0 running in PVH
>>> mode as in this case there is no grub or OVMF involved for filling in
>>> the boot parameters.
>> We are going to continue supporting direct boot of unprivileged guests
>> too so this entry point will be needed not for dom0 only.
> Sure, but using e.g. grub in this case would be an alternative. For Dom0
> this alternative isn't existing. So this entry is mandatory, not a "nice
> to have".

Right, I was just pointing out that the way the message is phrased makes
it sounds (to me at least) as if dom0 is the only reason for the
dedicated entry point.

-boris