On Fri, 27 Jul 2012, Ian Campbell wrote:

On Thu, 2012-07-26 at 16:33 +0100, Stefano Stabellini wrote:

quoted

Check for a "/xen" node in the device tree, if it is present set
xen_domain_type to XEN_HVM_DOMAIN and continue initialization.

Map the real shared info page using XENMEM_add_to_physmap with
XENMAPSPACE_shared_info.

Signed-off-by: Stefano Stabellini <redacted>
---
 arch/arm/xen/enlighten.c |   56 ++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 56 insertions(+), 0 deletions(-)

diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
index d27c2a6..8c923af 100644
--- a/arch/arm/xen/enlighten.c
+++ b/arch/arm/xen/enlighten.c

@@ -5,6 +5,9 @@
 #include <asm/xen/hypervisor.h>
 #include <asm/xen/hypercall.h>
 #include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_irq.h>
+#include <linux/of_address.h>
 
 struct start_info _xen_start_info;
 struct start_info *xen_start_info = &_xen_start_info;

@@ -33,3 +36,56 @@ int xen_remap_domain_mfn_range(struct vm_area_struct *vma,
 	return -ENOSYS;
 }
 EXPORT_SYMBOL_GPL(xen_remap_domain_mfn_range);
+
+/*
+ * == Xen Device Tree format ==
+ * - /xen node;
+ * - compatible "arm,xen";
+ * - one interrupt for Xen event notifications;
+ * - one memory region to map the grant_table.
+ */
+static int __init xen_guest_init(void)
+{
+	int cpu;
+	struct xen_add_to_physmap xatp;
+	static struct shared_info *shared_info_page = 0;
+	struct device_node *node;
+
+	node = of_find_compatible_node(NULL, NULL, "arm,xen");
+	if (!node) {
+		pr_info("No Xen support\n");
+		return 0;
+	}

This should either only print in the success case (to avoid spamming
everyone) or we need a little bit of infrastructure like on x86 so that
we print exactly one of:
	"Booting natively on bearmetal"
	"Booting paravirtualised on %s", hypervisor->name

This function is only going to be called once (actually it might be
called twice with the change introduced by "xen/arm: Introduce
xen_guest_init").

I thought that it would be an acceptible level of verbosity for pr_info.
Maybe I should just turn the pr_info into pr_debug?

quoted

+	xen_domain_type = XEN_HVM_DOMAIN;
+
+	if (!shared_info_page)
+		shared_info_page = (struct shared_info *)
+			get_zeroed_page(GFP_KERNEL);
+	if (!shared_info_page) {
+		pr_err("not enough memory");
+		return -ENOMEM;
+	}
+	xatp.domid = DOMID_SELF;
+	xatp.idx = 0;
+	xatp.space = XENMAPSPACE_shared_info;
+	xatp.gpfn = __pa(shared_info_page) >> PAGE_SHIFT;
+	if (HYPERVISOR_memory_op(XENMEM_add_to_physmap, &xatp))
+		BUG();
+
+	HYPERVISOR_shared_info = (struct shared_info *)shared_info_page;
+
+	/* xen_vcpu is a pointer to the vcpu_info struct in the shared_info
+	 * page, we use it in the event channel upcall and in some pvclock
+	 * related functions. We don't need the vcpu_info placement
+	 * optimizations because we don't use any pv_mmu or pv_irq op on
+	 * HVM.
+	 * When xen_hvm_init_shared_info is run at boot time only vcpu 0 is
+	 * online but xen_hvm_init_shared_info is run at resume time too and
+	 * in that case multiple vcpus might be online. */
+	for_each_online_cpu(cpu) {
+		per_cpu(xen_vcpu, cpu) =
+			&HYPERVISOR_shared_info->vcpu_info[cpu];

On ARM the shared info contains exactly 1 CPU (the boot CPU). The guest
is required to use VCPUOP_register_vcpu_info to place vcpu info for
secondary CPUs as they are brought up.

OK