Re: [PATCH v5 4/4] x86/xen: Add "nopv" support for HVM guest

[Zhenzhong Duan]

On 2019/7/5 21:06, Boris Ostrovsky wrote:
> On 7/2/19 9:19 PM, Zhenzhong Duan wrote:
> > PVH guest needs PV extentions to work, so "nopv" parameter should be
> > ignored for PVH but not for HVM guest.
> >
> > If PVH guest boots up via the Xen-PVH boot entry, xen_pvh is set early,
> > we know it's PVH guest and ignore "nopv" parameter directly.
> >
> > If PVH guest boots up via the normal boot entry same as HVM guest, it's
> > hard to distinguish PVH and HVM guest at that time.
> >
> > To handle that case, add a new function xen_hvm_nopv_guest_late_init()
> > to detect PVH at a late time and panic itself if nopv enabled for a
> > PVH guest.
> >
> > Signed-off-by: Zhenzhong Duan<zhenzhong.duan@xxxxxxxxxx>
> > Cc: Boris Ostrovsky<boris.ostrovsky@xxxxxxxxxx>
> > Cc: Juergen Gross<jgross@xxxxxxxx>
> > Cc: Stefano Stabellini<sstabellini@xxxxxxxxxx>
> > Cc: Thomas Gleixner<tglx@xxxxxxxxxxxxx>
> > Cc: Ingo Molnar<mingo@xxxxxxxxxx>
> > Cc: Borislav Petkov<bp@xxxxxxxxx>
> > ---
> >   arch/x86/xen/enlighten_hvm.c | 27 +++++++++++++++++++++++++++
> >   1 file changed, 27 insertions(+)
> >
> > diff --git a/arch/x86/xen/enlighten_hvm.c b/arch/x86/xen/enlighten_hvm.c
> > index 1756cf7..09a010a 100644
> > --- a/arch/x86/xen/enlighten_hvm.c
> > +++ b/arch/x86/xen/enlighten_hvm.c
> > @@ -231,11 +231,37 @@ bool __init xen_hvm_need_lapic(void)
> >   	return true;
> >   }
> >   
> > +static __init void xen_hvm_nopv_guest_late_init(void)
> > +{
> > +#ifdef CONFIG_XEN_PVH
> > +	if (x86_platform.legacy.rtc || !x86_platform.legacy.no_vga)
> > +		return;
> > +
> > +	/* PVH detected. */
> > +	xen_pvh = true;
> > +
> > +	panic("\"nopv\" and \"xen_nopv\" parameters are unsupported in PVH guest.");
> > +#endif
> > +}
> Can't all of this be done in xen_hvm_guest_late_init()? It has the same
> tests already and it seems to me you should be able to panic from there.

Indeed, I didn't realize this, thanks for pointing, I'll fix it.

Zhenzhong