xen/x86: generalize preferred console model from PV to PVH Dom0

Without announcing hvc0 as preferred it won't get used as long as tty0
gets registered earlier. This is particularly problematic with there not
being any screen output for PVH Dom0 when the screen is in graphics
mode, as the necessary information doesn't get conveyed yet from the
hypervisor.

Follow PV's model, but be conservative and do this for Dom0 only for
now.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/582328b6-c86c-37f3-d802-5539b7a86736@suse.comSigned-off-by: Juergen Gross <jgross@suse.com>

arch/x86/xen/enlighten.c

@@ -3,6 +3,7 @@
 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
 #include <linux/memblock.h>
 #endif
+#include <linux/console.h>
 #include <linux/cpu.h>
 #include <linux/kexec.h>
 #include <linux/slab.h>
@@ -18,6 +19,7 @@
 #include <asm/xen/hypervisor.h>
 #include <asm/cpu.h>
 #include <asm/e820/api.h> 
+#include <asm/setup.h>
 
 #include "xen-ops.h"
 #include "smp.h"
@@ -274,6 +276,16 @@ bool xen_running_on_version_or_later(unsigned int major, unsigned int minor)
 	return false;
 }
 
+void __init xen_add_preferred_consoles(void)
+{
+	add_preferred_console("xenboot", 0, NULL);
+	if (!boot_params.screen_info.orig_video_isVGA)
+		add_preferred_console("tty", 0, NULL);
+	add_preferred_console("hvc", 0, NULL);
+	if (boot_params.screen_info.orig_video_isVGA)
+		add_preferred_console("tty", 0, NULL);
+}
+
 void xen_reboot(int reason)
 {
 	struct sched_shutdown r = { .reason = reason };

arch/x86/xen/enlighten_pv.c

@@ -28,7 +28,6 @@
 #include <linux/mm.h>
 #include <linux/page-flags.h>
 #include <linux/highmem.h>
-#include <linux/console.h>
 #include <linux/pci.h>
 #include <linux/gfp.h>
 #include <linux/edd.h>
@@ -1392,12 +1391,7 @@ asmlinkage __visible void __init xen_start_kernel(void)
 #endif
 	}
 
-	add_preferred_console("xenboot", 0, NULL);
-	if (!boot_params.screen_info.orig_video_isVGA)
-		add_preferred_console("tty", 0, NULL);
-	add_preferred_console("hvc", 0, NULL);
-	if (boot_params.screen_info.orig_video_isVGA)
-		add_preferred_console("tty", 0, NULL);
+	xen_add_preferred_consoles();
 
 #ifdef CONFIG_PCI
 	/* PCI BIOS service won't work from a PV guest. */

arch/x86/xen/enlighten_pvh.c

@@ -36,6 +36,9 @@ void __init xen_pvh_init(struct boot_params *boot_params)
 	pfn = __pa(hypercall_page);
 	wrmsr_safe(msr, (u32)pfn, (u32)(pfn >> 32));
 
+	if (xen_initial_domain())
+		x86_init.oem.arch_setup = xen_add_preferred_consoles;
+
 	xen_efi_init(boot_params);
 }
 

arch/x86/xen/xen-ops.h

@@ -118,6 +118,8 @@ static inline void __init xen_init_vga(const struct dom0_vga_console_info *info,
 }
 #endif
 
+void xen_add_preferred_consoles(void);
+
 void __init xen_init_apic(void);
 
 #ifdef CONFIG_XEN_EFI