arm,arm64/xen: move Xen initialization earlier

Currently, Xen is initialized/discovered in an initcall. This doesn't
allow us to support earlyprintk or choosing the preferred console when
running on Xen.

The current function xen_guest_init is now split in 2 parts:
    - xen_early_init: Check if there is a Xen node in the device tree
    and setup domain type
    - xen_guest_init: Retrieve the information from the device node and
    initialize Xen (grant table, shared page...)

The former is called in setup_arch, while the latter is an initcall.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: Julien Grall <julien.grall@linaro.org>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Will Deacon <will.deacon@arm.com>

arch/arm/include/asm/xen/hypervisor.h

@@ -1,6 +1,8 @@
 #ifndef _ASM_ARM_XEN_HYPERVISOR_H
 #define _ASM_ARM_XEN_HYPERVISOR_H
 
+#include <linux/init.h>
+
 extern struct shared_info *HYPERVISOR_shared_info;
 extern struct start_info *xen_start_info;
 
@@ -18,4 +20,10 @@ static inline enum paravirt_lazy_mode paravirt_get_lazy_mode(void)
 
 extern struct dma_map_ops *xen_dma_ops;
 
+#ifdef CONFIG_XEN
+void __init xen_early_init(void);
+#else
+static inline void xen_early_init(void) { return; }
+#endif
+
 #endif /* _ASM_ARM_XEN_HYPERVISOR_H */

arch/arm/kernel/setup.c

@@ -46,6 +46,7 @@
 #include <asm/cacheflush.h>
 #include <asm/cachetype.h>
 #include <asm/tlbflush.h>
+#include <asm/xen/hypervisor.h>
 
 #include <asm/prom.h>
 #include <asm/mach/arch.h>
@@ -951,6 +952,7 @@ void __init setup_arch(char **cmdline_p)
 
 	arm_dt_init_cpu_maps();
 	psci_init();
+	xen_early_init();
 #ifdef CONFIG_SMP
 	if (is_smp()) {
 		if (!mdesc->smp_init || !mdesc->smp_init()) {

arch/arm/xen/enlighten.c

@@ -53,6 +53,8 @@ EXPORT_SYMBOL_GPL(xen_platform_pci_unplug);
 
 static __read_mostly unsigned int xen_events_irq;
 
+static __initdata struct device_node *xen_node;
+
 int xen_remap_domain_mfn_array(struct vm_area_struct *vma,
 			       unsigned long addr,
 			       xen_pfn_t *mfn, int nr,
@@ -150,42 +152,28 @@ static irqreturn_t xen_arm_callback(int irq, void *arg)
  * documentation of the Xen Device Tree format.
  */
 #define GRANT_TABLE_PHYSADDR 0
-static int __init xen_guest_init(void)
+void __init xen_early_init(void)
 {
-	struct xen_add_to_physmap xatp;
-	static struct shared_info *shared_info_page = 0;
-	struct device_node *node;
 	int len;
 	const char *s = NULL;
 	const char *version = NULL;
 	const char *xen_prefix = "xen,xen-";
-	struct resource res;
-	phys_addr_t grant_frames;
 
-	node = of_find_compatible_node(NULL, NULL, "xen,xen");
+	xen_node = of_find_compatible_node(NULL, NULL, "xen,xen");
-	if (!node) {
+	if (!xen_node) {
 		pr_debug("No Xen support\n");
-		return 0;
+		return;
 	}
-	s = of_get_property(node, "compatible", &len);
+	s = of_get_property(xen_node, "compatible", &len);
 	if (strlen(xen_prefix) + 3  < len &&
 			!strncmp(xen_prefix, s, strlen(xen_prefix)))
 		version = s + strlen(xen_prefix);
 	if (version == NULL) {
 		pr_debug("Xen version not found\n");
-		return 0;
+		return;
-	}
-	if (of_address_to_resource(node, GRANT_TABLE_PHYSADDR, &res))
-		return 0;
-	grant_frames = res.start;
-	xen_events_irq = irq_of_parse_and_map(node, 0);
-	if (!xen_events_irq) {
-		pr_debug("Xen event channel interrupt not found\n");
-		return -ENODEV;
 	}
 
-	pr_info("Xen %s support found, events_irq=%d gnttab_frame=%pa\n",
+	pr_info("Xen %s support found\n", version);
-			version, xen_events_irq, &grant_frames);
 
 	xen_domain_type = XEN_HVM_DOMAIN;
 
@@ -195,10 +183,32 @@ static int __init xen_guest_init(void)
 		xen_start_info->flags |= SIF_INITDOMAIN|SIF_PRIVILEGED;
 	else
 		xen_start_info->flags &= ~(SIF_INITDOMAIN|SIF_PRIVILEGED);
+}
+
+static int __init xen_guest_init(void)
+{
+	struct xen_add_to_physmap xatp;
+	struct shared_info *shared_info_page = NULL;
+	struct resource res;
+	phys_addr_t grant_frames;
+
+	if (!xen_domain())
+		return 0;
+
+	if (of_address_to_resource(xen_node, GRANT_TABLE_PHYSADDR, &res)) {
+		pr_err("Xen grant table base address not found\n");
+		return -ENODEV;
+	}
+	grant_frames = res.start;
+
+	xen_events_irq = irq_of_parse_and_map(xen_node, 0);
+	if (!xen_events_irq) {
+		pr_err("Xen event channel interrupt not found\n");
+		return -ENODEV;
+	}
+
+	shared_info_page = (struct shared_info *)get_zeroed_page(GFP_KERNEL);
 
-	if (!shared_info_page)
-		shared_info_page = (struct shared_info *)
-			get_zeroed_page(GFP_KERNEL);
 	if (!shared_info_page) {
 		pr_err("not enough memory\n");
 		return -ENOMEM;

arch/arm64/kernel/setup.c

@@ -64,6 +64,7 @@
 #include <asm/psci.h>
 #include <asm/efi.h>
 #include <asm/virt.h>
+#include <asm/xen/hypervisor.h>
 
 unsigned long elf_hwcap __read_mostly;
 EXPORT_SYMBOL_GPL(elf_hwcap);
@@ -416,6 +417,7 @@ void __init setup_arch(char **cmdline_p)
 		psci_acpi_init();
 		acpi_init_cpus();
 	}
+	xen_early_init();
 
 #ifdef CONFIG_SMP
 	smp_build_mpidr_hash();