linux-kernel - Re: [PATCH v12 07/18] xen/pvh: Setup up shared

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Message-ID: <20140103143902.GB27019@phenom.dumpdata.com>
Date:	Fri, 3 Jan 2014 09:39:02 -0500
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	David Vrabel <david.vrabel@...rix.com>
Cc:	linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org,
	boris.ostrovsky@...cle.com, stefano.stabellini@...citrix.com,
	mukesh.rathor@...cle.com
Subject: Re: [PATCH v12 07/18] xen/pvh: Setup up shared_info.

On Thu, Jan 02, 2014 at 11:27:56AM +0000, David Vrabel wrote:
> On 01/01/14 04:35, Konrad Rzeszutek Wilk wrote:
> > From: Mukesh Rathor <mukesh.rathor@...cle.com>
> > 
> > For PVHVM the shared_info structure is provided via the same way
> > as for normal PV guests (see include/xen/interface/xen.h).
> > 
> > That is during bootup we get 'xen_start_info' via the %esi register
> > in startup_xen. Then later we extract the 'shared_info' from said
> > structure (in xen_setup_shared_info) and start using it.
> > 
> > The 'xen_setup_shared_info' is all setup to work with auto-xlat
> > guests, but there are two functions which it calls that are not:
> > xen_setup_mfn_list_list and xen_setup_vcpu_info_placement.
> > This patch modifies those to work in auto-xlat mode.
> [...]
> > --- a/arch/x86/xen/enlighten.c
> > +++ b/arch/x86/xen/enlighten.c
> > @@ -1147,8 +1147,9 @@ void xen_setup_vcpu_info_placement(void)
> >  		xen_vcpu_setup(cpu);
> >  
> >  	/* xen_vcpu_setup managed to place the vcpu_info within the
> > -	   percpu area for all cpus, so make use of it */
> > -	if (have_vcpu_info_placement) {
> > +	 * percpu area for all cpus, so make use of it. Note that for
> > +	 * PVH we want to use native IRQ mechanism. */
> > +	if (have_vcpu_info_placement && !xen_pvh_domain()) {
> >  		pv_irq_ops.save_fl = __PV_IS_CALLEE_SAVE(xen_save_fl_direct);
> >  		pv_irq_ops.restore_fl = __PV_IS_CALLEE_SAVE(xen_restore_fl_direct);
> >  		pv_irq_ops.irq_disable = __PV_IS_CALLEE_SAVE(xen_irq_disable_direct);
> 
> Should this be in a separate patch: "xen/pvh: use native irq ops"?

On a second thought I think not. The reason is explained in the commit
description:

 The 'xen_setup_shared_info' is all setup to work with auto-xlat
 guests, but there are two functions which it calls that are not:
 xen_setup_mfn_list_list and xen_setup_vcpu_info_placement.
 This patch modifies those to work in auto-xlat mode.

If we move this to another patch, it is going to be mostly the same
comment and this patch will feel unfinished.


> 
> David
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