[PATCH v12 11/18] xen/pvh: Piggyback on PVHVM for event channels (v2)

[Konrad Rzeszutek Wilk]

From: Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>

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.

We will piggyback on how the event channel mechanism is
used in PVHVM - that is we want the normal native IRQ mechanism
and we will install a vector (hvm callback) for which we
will call the event channel mechanism.

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@xxxxxxxxxx>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 arch/x86/xen/irq.c   |  5 ++++-
 drivers/xen/events.c | 16 ++++++++++------
 2 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/arch/x86/xen/irq.c b/arch/x86/xen/irq.c
index 0da7f86..76ca326 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..bf8fb29 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -1908,20 +1908,24 @@ void __init xen_init_IRQ(void)
 	pirq_needs_eoi = pirq_needs_eoi_flag;
 
 #ifdef CONFIG_X86
-	if (xen_hvm_domain()) {
+	if (xen_pv_domain()) {
+		irq_ctx_init(smp_processor_id());
+		if (xen_initial_domain())
+			pci_xen_initial_domain();
+	}
+	if (xen_feature(XENFEAT_hvm_callback_vector))
 		xen_callback_vector();
+
+	if (xen_hvm_domain()) {
 		native_init_IRQ();
 		/* pci_xen_hvm_init must be called after native_init_IRQ so that
 		 * __acpi_register_gsi can point at the right function */
 		pci_xen_hvm_init();
-	} else {
+	} else if (!xen_pvh_domain()) {
+		/* TODO: No PVH support for PIRQ EOI */
 		int rc;
 		struct physdev_pirq_eoi_gmfn eoi_gmfn;
 
-		irq_ctx_init(smp_processor_id());
-		if (xen_initial_domain())
-			pci_xen_initial_domain();
-
 		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);
-- 
1.8.3.1

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