xen/dom0less: turn max_init_domid into a common variable

Until now every architecture carried its own notion of max_init_domid:
Arm defined a real variable (declared in asm/setup.h, defined in
setup.c), while ppc, riscv and x86 each provided a "#define
max_init_domid (0)" stub in their asm/setup.h. This duplicated the same
declaration across all arches and placed a purely dom0less concept in
arch setup headers.

Now that the dom0less build code lives in common (xen/common/
device-tree/dom0less-build.c sets max_init_domid, and the console
serial-input switcher reads it), there is no reason for the symbol to be
per-arch. Provide a single declaration in <xen/dom0less-build.h>, with
the !CONFIG_DOM0LESS_BOOT stub kept there as well, so there is one source
of truth and the arch headers no longer need to mention it. Update
console.c to include <xen/dom0less-build.h> for the declaration instead
of relying on asm/setup.h, and drop the now unneeded <asm/setup.h>
include.

Place the definition in xen/common/domid.c rather than in dom0less-
build.c. The latter is built as dom0less-build.init.o, i.e. the whole
object is relocated into the .init.* sections and freed after boot,
whereas max_init_domid must outlive boot because it is read at runtime
by the console serial-input switcher. domid.c is always linked (obj-y)
and resides in regular (non-init) sections, so it is a correct home for
the variable. It is marked __ro_after_init since it is only updated
while creating boot-time domains and read-only afterwards, and guarded
by CONFIG_DOM0LESS_BOOT as domid.c itself is unconditional.

While at it, make <xen/dom0less-build.h> self-contained: it includes
<public/xen.h>, which uses the fixed-width types provided by
<xen/types.h>, so include the latter explicitly rather than relying on
the includer having pulled it in first. This becomes necessary as soon
as <xen/dom0less-build.h> comes first in an alphabetically sorted
include list, as it now does in domid.c.

Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Michal Orzel <michal.orzel@amd.com>

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

@@ -25,8 +25,6 @@ struct map_range_data
     struct rangeset *irq_ranges;
 };
 
-extern domid_t max_init_domid;
-
 void copy_from_paddr(void *dst, paddr_t paddr, unsigned long len);
 
 size_t estimate_efi_size(unsigned int mem_nr_banks);

xen/arch/arm/setup.c

@@ -62,8 +62,6 @@ struct cpuinfo_arm __read_mostly system_cpuinfo;
 bool __read_mostly acpi_disabled;
 #endif
 
-domid_t __read_mostly max_init_domid;
-
 static __used void noreturn init_done(void)
 {
     /* Must be done past setting system_state. */

xen/arch/ppc/include/asm/setup.h

@@ -1,6 +1,4 @@
 #ifndef __ASM_PPC_SETUP_H__
 #define __ASM_PPC_SETUP_H__
 
-#define max_init_domid (0)
-
 #endif /* __ASM_PPC_SETUP_H__ */

xen/arch/riscv/include/asm/setup.h

@@ -5,8 +5,6 @@
 
 #include <xen/types.h>
 
-#define max_init_domid (0)
-
 void setup_mm(void);
 
 void copy_from_paddr(void *dst, paddr_t paddr, unsigned long len);

xen/arch/x86/include/asm/setup.h

@@ -68,6 +68,4 @@ extern bool opt_dom0_verbose;
 extern bool opt_dom0_cpuid_faulting;
 extern bool opt_dom0_msr_relaxed;
 
-#define max_init_domid (0)
-
 #endif

xen/common/domid.c

@@ -8,8 +8,13 @@
  * Copyright 2025 Ford Motor Company
  */
 
+#include <xen/dom0less-build.h>
 #include <xen/domain.h>
 
+#ifdef CONFIG_DOM0LESS_BOOT
+domid_t __ro_after_init max_init_domid;
+#endif
+
 static DEFINE_SPINLOCK(domid_lock);
 static DECLARE_BITMAP(domid_bitmap, DOMID_FIRST_RESERVED);
 

xen/drivers/char/console.c

@@ -30,7 +30,7 @@
 #include <xen/early_printk.h>
 #include <xen/warning.h>
 #include <xen/pv_console.h>
-#include <asm/setup.h>
+#include <xen/dom0less-build.h>
 #include <xen/sections.h>
 #include <xen/consoled.h>
 

xen/include/xen/dom0less-build.h

@@ -4,6 +4,9 @@
 #define XEN_DOM0LESS_BUILD_H
 
 #include <xen/stdbool.h>
+#include <xen/types.h>
+
+#include <public/xen.h>
 
 struct domain;
 
@@ -13,6 +16,9 @@ struct boot_domain;
 struct dt_device_node;
 struct kernel_info;
 
+/* Highest domain ID assigned to a boot-time (dom0less) domain. */
+extern domid_t max_init_domid;
+
 /*
  * List of possible features for dom0less domUs
  *
@@ -72,6 +78,8 @@ static inline bool is_dom0less_mode(void)
 }
 static inline void set_xs_domain(struct domain *d) {}
 
+#define max_init_domid 0
+
 #endif /* CONFIG_DOM0LESS_BOOT */
 
 #endif /* __ASM_GENERIC_DOM0LESS_BUILD_H__ */