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

[Boris Ostrovsky]

On 01/27/2016 09:50 AM, David Vrabel wrote:
> On 27/01/16 14:42, Konrad Rzeszutek Wilk wrote:
> > On Tue, Jan 26, 2016 at 08:54:56PM -0800, Luis R. Rodriguez wrote:
> > > On Jan 26, 2016 6:16 PM, "Luis R. Rodriguez" <mcgrof@xxxxxxxx> wrote:
> > > > On Tue, Jan 26, 2016 at 4:04 PM, Luis R. Rodriguez <mcgrof@xxxxxxxx>
> > > wrote:
> > > > > You go:
> > > > >
> > > > > hvmlite_start_xen() -->
> > > > >          HVM stub
> > > > >          startup_64() | (startup_32()
> > > > Hrm, does HVMlite work well with load_ucode_bsp(), note the patches to
> > > > rebrand pv_enabled() to pv_legacy() or whatever, this PV type will not
> > > > be legacy or crap / old, so we'd need a way to catch it if we should
> > > > not use that code for this PV type. This begs the question, are you
> > > > also sure other callers in startup_32() or startup_64() might be OK as
> > > > well where previously guarded with pv_enabled() ?
> > > Actually this call can't be used, and if early code used it prior to
> > > setup_arch() it'd be a bug as its only properly set until later. Vetting
> > > for correctness of all code call is still required though and perhaps we do
> > > need something to catch now this PV type on early code such as this one if
> > > we don't want it. From what I've gathered before on other bsp ucode we
> > > don't want ucode loaded for PV guest types through these mechanisms.
> > It may help to not think of PVH/hvmlite as PV. It really is HVM with a lot
> > of emulated devices removed.
> >
> > How does early microcode work on EFI? Does the EFI stub code have an early
> > microcode loading code ?
> Surely the interesting comparison here is how is (early) microcode
> loading disabled in KVM guests?  We should use the same mechanism for
> HVMlite guests.


Why would we ever want to have a guest load microcode during boot? I can 
see how a (privileged) guest may want to load microcode from a shell 
(via microcode driver).

-boris