Re: [PATCH v1 04/12] xen/hvmlite: Bootstrap HVMlite guest

From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
To: "Luis R. Rodriguez" <mcgrof@kernel.org>,
	Takashi Iwai <tiwai@suse.de>, Avi Kivity <avi@redhat.com>,
	Joerg Roedel <jroedel@suse.de>, "H. Peter Anvin" <hpa@zytor.com>,
	Borislav Petkov <bp@suse.de>,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	Andy Lutomirski <luto@amacapital.net>,
	Andrew Cooper <andrew.cooper3@citrix.com>
Cc: "Juergen Gross" <jgross@suse.com>,
	"Jeremy Fitzhardinge" <jeremy@goop.org>,
	"Rusty Russell" <rusty@rustcorp.com.au>,
	"X86 ML" <x86@kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"David Vrabel" <david.vrabel@citrix.com>,
	xen-devel@lists.xenproject.org,
	"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [PATCH v1 04/12] xen/hvmlite: Bootstrap HVMlite guest
Date: Wed, 27 Jan 2016 18:58:56 -0500	[thread overview]
Message-ID: <56A959C0.70103__17068.5871890329$1453939250$gmane$org@oracle.com> (raw)
In-Reply-To: <CAB=NE6U_shcYEO3AzQT7YAzramDmVN3u4Guk=ZGOXfeV+PLnDQ@mail.gmail.com>

On 01/27/2016 02:00 PM, Luis R. Rodriguez wrote:
> On Wed, Jan 27, 2016 at 10:48 AM, Luis R. Rodriguez <mcgrof@kernel.org> wrote:
>> Worth mentioning here also is hpa's clarification on when subarch type
>> PC (0) should be used: [it should be used if the hardware is]
>> "enumerable using standard PC mechanisms (PCI, ACPI) and doesn't need
>> a special boot flow" -- does that fit HVMLite's description so far? If
>> so then The Xen subarch may need to be redefined as well to be clear
>> what it means. I don't think we need to be precise but at the very
>> least cover grounds to enable the definitions to meet its actual use
>> to not confuse users.
> Another thing to consider for HVMlite is that if the 0 subarch (PC) is
> used in light of my linker table work and x86's use of it with the
> subarch and supported subarch bitmask, is that it would also mean
> HVMLite would run all routines currently pegged as needing PC type
> (the current KVM and bare metal path) and it would mean not running
> anything only pegged with Xen subarch type (but note that today Xen
> doesn't even set the subarch type). If there is nothing in common
> between PV and HVMlite (no x86 init calls to share), and if HVMLite
> *can* call *alllllllll* PC init calls, then by all means this is fine,

Yes, that's the idea. HVMlite jumps to startup_32|64 from the stub and 
runs from there with subarch 0.

-boris

> and if we just need to distinguish stuff between PC types that's fine,
> it may still be possible to further extend hypervisor_type to the x86
> init calls I'm adding as another supported_hyper_types to ensure even
> though a subarch is being used, that we also check the supported
> hypervisor type as well.
>
>   Luis