[PATCH v7 02/20] 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.

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.

Signed-off-by: Oleksii Kurochko <[email protected]>
Reviewed-by: Jan Beulich <[email protected]>
---
Changes in v6-7:
 - Nothing changed. Only rebase.
---
Changes in v5:
 - Add Reviewed-by: Jan Beulich <[email protected]>
---
Changes in v4:
 - New patch.
---
---
 xen/arch/arm/include/asm/setup.h   | 2 --
 xen/arch/arm/setup.c               | 2 --
 xen/arch/ppc/include/asm/setup.h   | 2 --
 xen/arch/riscv/include/asm/setup.h | 2 --
 xen/arch/x86/include/asm/setup.h   | 2 --
 xen/common/domid.c                 | 5 +++++
 xen/drivers/char/console.c         | 1 +
 xen/include/xen/dom0less-build.h   | 7 +++++++
 8 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/xen/arch/arm/include/asm/setup.h b/xen/arch/arm/include/asm/setup.h
index 0adfa4993a8f..2af780512540 100644
--- a/xen/arch/arm/include/asm/setup.h
+++ b/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);
diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
index 6310a47d68b6..86532d0a35b6 100644
--- a/xen/arch/arm/setup.c
+++ b/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. */
diff --git a/xen/arch/ppc/include/asm/setup.h b/xen/arch/ppc/include/asm/setup.h
index e4f64879b68c..956fa6985adb 100644
--- a/xen/arch/ppc/include/asm/setup.h
+++ b/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__ */
diff --git a/xen/arch/riscv/include/asm/setup.h b/xen/arch/riscv/include/asm/setup.h
index 2215894cfbb1..73ce2f293348 100644
--- a/xen/arch/riscv/include/asm/setup.h
+++ b/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);
diff --git a/xen/arch/x86/include/asm/setup.h b/xen/arch/x86/include/asm/setup.h
index b01e83a8ed9f..5925c5f39cff 100644
--- a/xen/arch/x86/include/asm/setup.h
+++ b/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
diff --git a/xen/common/domid.c b/xen/common/domid.c
index b0258e477c1a..cd46cf952be6 100644
--- a/xen/common/domid.c
+++ b/xen/common/domid.c
@@ -9,6 +9,11 @@
  */
 
 #include <xen/domain.h>
+#include <xen/dom0less-build.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);
diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
index ea4e3ff34178..4c735cc04c67 100644
--- a/xen/drivers/char/console.c
+++ b/xen/drivers/char/console.c
@@ -31,6 +31,7 @@
 #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>
 
diff --git a/xen/include/xen/dom0less-build.h b/xen/include/xen/dom0less-build.h
index 4118dec76c0a..8d4da16d1f0a 100644
--- a/xen/include/xen/dom0less-build.h
+++ b/xen/include/xen/dom0less-build.h
@@ -5,6 +5,8 @@
 
 #include <xen/stdbool.h>
 
+#include <public/xen.h>
+
 struct domain;
 
 #ifdef CONFIG_DOM0LESS_BOOT
@@ -13,6 +15,9 @@ 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 +77,8 @@ 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__ */
-- 
2.55.0