x86/virt/xen: Use guest_late_init to detect Xen PVH guest

In case we are booted via the default boot entry by a generic loader
like grub or OVMF it is necessary to distinguish between a HVM guest
with a device model supporting legacy devices and a PVH guest without
device model.

PVH guests will always have x86_platform.legacy.no_vga set and
x86_platform.legacy.rtc cleared, while both won't be true for HVM
guests.

Test for both conditions in the guest_late_init hook and set xen_pvh
to true if they are met.

Move some of the early PVH initializations to the new hook in order
to avoid duplicated code.

Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: boris.ostrovsky@oracle.com
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/20171109132739.23465-6-jgross@suse.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/xen/enlighten_hvm.c

@@ -1,3 +1,4 @@
+#include <linux/acpi.h>
 #include <linux/cpu.h>
 #include <linux/kexec.h>
 #include <linux/memblock.h>
@@ -188,8 +189,6 @@ static void __init xen_hvm_guest_init(void)
 	xen_hvm_init_time_ops();
 	xen_hvm_init_mmu_ops();
 
-	if (xen_pvh_domain())
-		machine_ops.emergency_restart = xen_emergency_restart;
 #ifdef CONFIG_KEXEC_CORE
 	machine_ops.shutdown = xen_hvm_shutdown;
 	machine_ops.crash_shutdown = xen_hvm_crash_shutdown;
@@ -226,6 +225,26 @@ static uint32_t __init xen_platform_hvm(void)
 	return xen_cpuid_base();
 }
 
+static __init void xen_hvm_guest_late_init(void)
+{
+#ifdef CONFIG_XEN_PVH
+	/* Test for PVH domain (PVH boot path taken overrides ACPI flags). */
+	if (!xen_pvh &&
+	    (x86_platform.legacy.rtc || !x86_platform.legacy.no_vga))
+		return;
+
+	/* PVH detected. */
+	xen_pvh = true;
+
+	/* Make sure we don't fall back to (default) ACPI_IRQ_MODEL_PIC. */
+	if (!nr_ioapics && acpi_irq_model == ACPI_IRQ_MODEL_PIC)
+		acpi_irq_model = ACPI_IRQ_MODEL_PLATFORM;
+
+	machine_ops.emergency_restart = xen_emergency_restart;
+	pv_info.name = "Xen PVH";
+#endif
+}
+
 const __initconst struct hypervisor_x86 x86_hyper_xen_hvm = {
 	.name                   = "Xen HVM",
 	.detect                 = xen_platform_hvm,
@@ -233,5 +252,6 @@ const __initconst struct hypervisor_x86 x86_hyper_xen_hvm = {
 	.init.init_platform     = xen_hvm_guest_init,
 	.init.x2apic_available  = xen_x2apic_para_available,
 	.init.init_mem_mapping	= xen_hvm_init_mem_mapping,
+	.init.guest_late_init	= xen_hvm_guest_late_init,
 	.runtime.pin_vcpu       = xen_pin_vcpu,
 };

arch/x86/xen/enlighten_pvh.c

@@ -25,13 +25,6 @@ struct boot_params pvh_bootparams __attribute__((section(".data")));
 struct hvm_start_info pvh_start_info;
 unsigned int pvh_start_info_sz = sizeof(pvh_start_info);
 
-static void xen_pvh_arch_setup(void)
-{
-	/* Make sure we don't fall back to (default) ACPI_IRQ_MODEL_PIC. */
-	if (nr_ioapics == 0)
-		acpi_irq_model = ACPI_IRQ_MODEL_PLATFORM;
-}
-
 static void __init init_pvh_bootparams(void)
 {
 	struct xen_memory_map memmap;
@@ -102,6 +95,4 @@ void __init xen_prepare_pvh(void)
 	wrmsr_safe(msr, (u32)pfn, (u32)(pfn >> 32));
 
 	init_pvh_bootparams();
-
-	x86_init.oem.arch_setup = xen_pvh_arch_setup;
 }