[PATCH v6 38/44] x86/boot: introduce boot domain

["Daniel P. Smith" <dpsmith@xxxxxxxxxxxxxxxxxxxx>]

To begin moving toward allowing the hypervisor to construct more than one
domain at boot, a container is needed for a domain's build information.

Introduce a new header, <xen/asm/bootdomain.h>, that contains the initial
struct boot_domain that encapsulate the build information for a domain.

No functional change intended.

Signed-off-by: Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>
---
 xen/arch/x86/include/asm/bootdomain.h | 28 +++++++++++++++++++++++++++
 xen/arch/x86/include/asm/bootinfo.h   |  5 +++++
 xen/arch/x86/setup.c                  | 23 +++++++---------------
 3 files changed, 40 insertions(+), 16 deletions(-)
 create mode 100644 xen/arch/x86/include/asm/bootdomain.h

diff --git a/xen/arch/x86/include/asm/bootdomain.h 
b/xen/arch/x86/include/asm/bootdomain.h
new file mode 100644
index 000000000000..4285223ac5ab
--- /dev/null
+++ b/xen/arch/x86/include/asm/bootdomain.h
@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (c) 2024 Apertus Solutions, LLC
+ * Author: Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>
+ * Copyright (c) 2024 Christopher Clark <christopher.w.clark@xxxxxxxxx>
+ */
+
+#ifndef __XEN_X86_BOOTDOMAIN_H__
+#define __XEN_X86_BOOTDOMAIN_H__
+
+struct boot_module;
+
+struct boot_domain {
+    struct boot_module *kernel;
+    struct boot_module *ramdisk;
+};
+
+#endif
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/xen/arch/x86/include/asm/bootinfo.h 
b/xen/arch/x86/include/asm/bootinfo.h
index b65b55c0a2c2..476f71a7633b 100644
--- a/xen/arch/x86/include/asm/bootinfo.h
+++ b/xen/arch/x86/include/asm/bootinfo.h
@@ -9,10 +9,14 @@
 #define __XEN_X86_BOOTINFO_H__
 
 #include <xen/types.h>
+#include <asm/bootdomain.h>
 
 /* Max number of boot modules a bootloader can provide in addition to Xen */
 #define MAX_NR_BOOTMODS 63
 
+/* Max number of boot domains that Xen can construct */
+#define MAX_NR_BOOTDOMS 1
+
 /* Boot module binary type / purpose */
 enum bootmod_type {
     BOOTMOD_UNKNOWN,
@@ -63,6 +67,7 @@ struct boot_info {
 
     unsigned int nr_modules;
     struct boot_module mods[MAX_NR_BOOTMODS + 1];
+    struct boot_domain domains[MAX_NR_BOOTDOMS];
 };
 
 /*
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index ae027667eb82..ccb5052e18be 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -956,20 +956,10 @@ static struct domain *__init create_dom0(struct boot_info 
*bi)
             .misc_flags = opt_dom0_msr_relaxed ? XEN_X86_MSR_RELAXED : 0,
         },
     };
-    unsigned int mod_idx = first_boot_module_index(bi, BOOTMOD_RAMDISK);
-    struct boot_module *image, *initrd;
+    struct boot_domain *bd = &bi->domains[0];
     struct domain *d;
     domid_t domid;
 
-    /* Map boot_module to mb1 module for dom0 */
-    image = &bi->mods[0];
-
-    /* Map boot_module to mb1 module for initrd */
-    if ( mod_idx < 0 )
-        initrd = NULL;
-    else
-        initrd = &bi->mods[mod_idx];
-
     if ( opt_dom0_pvh )
     {
         dom0_cfg.flags |= (XEN_DOMCTL_CDF_hvm |
@@ -995,11 +985,10 @@ static struct domain *__init create_dom0(struct boot_info 
*bi)
         panic("Error creating d%uv0\n", domid);
 
     /* Grab the DOM0 command line. */
-    if ( image->cmdline || bi->kextra )
+    if ( bd->kernel->cmdline || bi->kextra )
     {
-        if ( image->cmdline )
-            safe_strcpy(cmdline,
-                        cmdline_cook(__va(image->cmdline),
+        if ( bd->kernel->cmdline )
+            safe_strcpy(cmdline, cmdline_cook(__va(bd->kernel->cmdline),
                         bi->loader));
 
         if ( bi->kextra )
@@ -1023,7 +1012,7 @@ static struct domain *__init create_dom0(struct boot_info 
*bi)
         }
     }
 
-    if ( construct_dom0(d, image, initrd, cmdline) != 0 )
+    if ( construct_dom0(d, bd->kernel, bd->ramdisk, cmdline) != 0 )
         panic("Could not construct domain 0\n");
 
     return d;
@@ -1203,6 +1192,7 @@ void asmlinkage __init noreturn __start_xen(unsigned long 
mbi_p)
     /* Dom0 kernel is always first */
     bi->mods[0].type = BOOTMOD_KERNEL;
     bi->mods[0].flags = BOOTMOD_FLAG_X86_CONSUMED;
+    bi->domains[0].kernel = &bi->mods[0];
 
     if ( pvh_boot )
     {
@@ -2086,6 +2076,7 @@ void asmlinkage __init noreturn __start_xen(unsigned long 
mbi_p)
     {
         bi->mods[initrdidx].type = BOOTMOD_RAMDISK;
         bi->mods[initrdidx].flags |= BOOTMOD_FLAG_X86_CONSUMED;
+        bi->domains[0].ramdisk = &bi->mods[initrdidx];
         if ( first_boot_module_index(bi, BOOTMOD_UNKNOWN) < MAX_NR_BOOTMODS )
             printk(XENLOG_WARNING
                    "Multiple initrd candidates, picking module #%u\n",
-- 
2.30.2