Re: [Xen-devel] [PATCH v11 09/12] xen/pvh: Piggyback on PVHVM XenBus and event channels for PVH.

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Wed, Dec 18, 2013 at 06:31:43PM +0000, Stefano Stabellini wrote:
> On Tue, 17 Dec 2013, Konrad Rzeszutek Wilk wrote:
> > From: Mukesh Rathor <mukesh.rathor@oracle.com>
> > 
> > PVH is a PV guest with a twist - there are certain things
> > that work in it like HVM and some like PV. There is
> > a similar mode - PVHVM where we run in HVM mode with
> > PV code enabled - and this patch explores that.
> > 
> > The most notable PV interfaces are the XenBus and event channels.
> > For PVH, we will use XenBus and event channels.
> > 
> > For the XenBus mechanism we piggyback on how it is done for
> > PVHVM guests.
> > 
> > Ditto for the event channel mechanism - we piggyback on PVHVM -
> > by setting up a specific vector callback and that
> > vector ends up calling the event channel mechanism to
> > dispatch the events as needed.
> > 
> > This means that from a pvops perspective, we can use
> > native_irq_ops instead of the Xen PV specific. Albeit in the
> > future we could support pirq_eoi_map. But that is
> > a feature request that can be shared with PVHVM.
> > 
> > Signed-off-by: Mukesh Rathor <mukesh.rathor@oracle.com>
> > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> > ---
> >  arch/x86/xen/enlighten.c           | 6 ++++++
> >  arch/x86/xen/irq.c                 | 5 ++++-
> >  drivers/xen/events.c               | 5 +++++
> >  drivers/xen/xenbus/xenbus_client.c | 3 ++-
> >  4 files changed, 17 insertions(+), 2 deletions(-)
> > 
> > diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> > index e420613..7fceb51 100644
> > --- a/arch/x86/xen/enlighten.c
> > +++ b/arch/x86/xen/enlighten.c
> > @@ -1134,6 +1134,8 @@ void xen_setup_shared_info(void)
> >  	/* In UP this is as good a place as any to set up shared info */
> >  	xen_setup_vcpu_info_placement();
> >  #endif
> > +	if (xen_pvh_domain())
> > +		return;
> >  
> >  	xen_setup_mfn_list_list();
> >  }
> 
> This is another one of those cases where I think we would benefit from
> introducing xen_setup_shared_info_pvh instead of adding more ifs here.

Actually this one can be removed.

> 
> 
> > @@ -1146,6 +1148,10 @@ void xen_setup_vcpu_info_placement(void)
> >  	for_each_possible_cpu(cpu)
> >  		xen_vcpu_setup(cpu);
> >  
> > +	/* PVH always uses native IRQ ops */
> > +	if (xen_pvh_domain())
> > +		return;
> > +
> >  	/* 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) {
> 
> Same here?

Hmmm, I wonder if the vcpu info placement could work with PVH.
> 
> 
> > diff --git a/arch/x86/xen/irq.c b/arch/x86/xen/irq.c
> > index 0da7f86..4f7f351 100644
> > --- a/arch/x86/xen/irq.c
> > +++ b/arch/x86/xen/irq.c
> > @@ -5,6 +5,7 @@
> >  #include <xen/interface/xen.h>
> >  #include <xen/interface/sched.h>
> >  #include <xen/interface/vcpu.h>
> > +#include <xen/features.h>
> >  #include <xen/events.h>
> >  
> >  #include <asm/xen/hypercall.h>
> > @@ -128,6 +129,8 @@ static const struct pv_irq_ops xen_irq_ops __initconst = {
> >  
> >  void __init xen_init_irq_ops(void)
> >  {
> > -	pv_irq_ops = xen_irq_ops;
> > +	/* For PVH we use default pv_irq_ops settings */
> > +	if (!xen_feature(XENFEAT_hvm_callback_vector))
> > +		pv_irq_ops = xen_irq_ops;
> >  	x86_init.irqs.intr_init = xen_init_IRQ;
> >  }
> > diff --git a/drivers/xen/events.c b/drivers/xen/events.c
> > index 4035e83..627a16a 100644
> > --- a/drivers/xen/events.c
> > +++ b/drivers/xen/events.c
> > @@ -1922,6 +1922,11 @@ void __init xen_init_IRQ(void)
> >  		if (xen_initial_domain())
> >  			pci_xen_initial_domain();
> >  
> > +		if (xen_feature(XENFEAT_hvm_callback_vector)) {
> > +			xen_callback_vector();
> > +			return;
> > +		}
> 
> There is another call to xen_callback_vector in the if
> (xen_hvm_domain()) path. Could we just move it out and have a single one
> if (xen_feature(XENFEAT_hvm_callback_vector))?

Sure. Good idea.
> 
> 
> >  		pirq_eoi_map = (void *)__get_free_page(GFP_KERNEL|__GFP_ZERO);
> >  		eoi_gmfn.gmfn = virt_to_mfn(pirq_eoi_map);
> >  		rc = HYPERVISOR_physdev_op(PHYSDEVOP_pirq_eoi_gmfn_v2, &eoi_gmfn);
> > diff --git a/drivers/xen/xenbus/xenbus_client.c b/drivers/xen/xenbus/xenbus_client.c
> > index ec097d6..7f7c454 100644
> > --- a/drivers/xen/xenbus/xenbus_client.c
> > +++ b/drivers/xen/xenbus/xenbus_client.c
> > @@ -45,6 +45,7 @@
> >  #include <xen/grant_table.h>
> >  #include <xen/xenbus.h>
> >  #include <xen/xen.h>
> > +#include <xen/features.h>
> >  
> >  #include "xenbus_probe.h"
> >  
> > @@ -743,7 +744,7 @@ static const struct xenbus_ring_ops ring_ops_hvm = {
> >  
> >  void __init xenbus_ring_ops_init(void)
> >  {
> > -	if (xen_pv_domain())
> > +	if (xen_pv_domain() && !xen_feature(XENFEAT_auto_translated_physmap))
> 
> Can we just change this test to
> 
> if (!xen_feature(XENFEAT_auto_translated_physmap))
> 
> ?

I think it can. I will try it out.
> 
> 
> >  		ring_ops = &ring_ops_pv;
> >  	else
> >  		ring_ops = &ring_ops_hvm;
> > -- 
> > 1.8.3.1
> > 
> > 
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> >