[Xen-devel] [PATCH 8/8] x86/setup: lift dom0 creation out into create_dom0() function

[David Woodhouse <dwmw2@infradead.org>]

From: David Woodhouse <dwmw@amazon.co.uk>

The creation of dom0 can be relatively self-contained. Shift it into
a separate function and simplify __start_xen() a little bit.

This is a cleanup in its own right, but will be even more desireable
when live update provides an alternative path through __start_xen()
that doesn't involve creating a new dom0 at all.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
 xen/arch/x86/setup.c | 169 +++++++++++++++++++++++--------------------
 1 file changed, 92 insertions(+), 77 deletions(-)

diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 10209e6bfb..9d86722ecd 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -678,6 +678,92 @@ static unsigned int __init copy_bios_e820(struct e820entry *map, unsigned int li
     return n;
 }
 
+static struct domain * __init create_dom0(const module_t *image,
+                                          unsigned long headroom,
+                                          module_t *initrd, char *kextra,
+                                          char *loader)
+{
+    struct xen_domctl_createdomain dom0_cfg = {
+        .flags = IS_ENABLED(CONFIG_TBOOT) ? XEN_DOMCTL_CDF_s3_integrity : 0,
+        .max_evtchn_port = -1,
+        .max_grant_frames = -1,
+        .max_maptrack_frames = -1,
+    };
+    struct domain *d;
+    char *cmdline;
+
+    if ( opt_dom0_pvh )
+    {
+        dom0_cfg.flags |= (XEN_DOMCTL_CDF_hvm |
+                           ((hvm_hap_supported() && !opt_dom0_shadow) ?
+                            XEN_DOMCTL_CDF_hap : 0));
+
+        dom0_cfg.arch.emulation_flags |=
+            XEN_X86_EMU_LAPIC | XEN_X86_EMU_IOAPIC | XEN_X86_EMU_VPCI;
+    }
+    dom0_cfg.max_vcpus = dom0_max_vcpus();
+
+    if ( iommu_enabled )
+        dom0_cfg.flags |= XEN_DOMCTL_CDF_iommu;
+
+    /* Create initial domain 0. */
+    d = domain_create(get_initial_domain_id(), &dom0_cfg, !pv_shim);
+    if ( IS_ERR(d) || (alloc_dom0_vcpu0(d) == NULL) )
+        panic("Error creating domain 0\n");
+
+    /* Grab the DOM0 command line. */
+    cmdline = (char *)(image->string ? __va(image->string) : NULL);
+    if ( (cmdline != NULL) || (kextra != NULL) )
+    {
+        static char __initdata dom0_cmdline[MAX_GUEST_CMDLINE];
+
+        cmdline = cmdline_cook(cmdline, loader);
+        safe_strcpy(dom0_cmdline, cmdline);
+
+        if ( kextra != NULL )
+            /* kextra always includes exactly one leading space. */
+            safe_strcat(dom0_cmdline, kextra);
+
+        /* Append any extra parameters. */
+        if ( skip_ioapic_setup && !strstr(dom0_cmdline, "noapic") )
+            safe_strcat(dom0_cmdline, " noapic");
+        if ( (strlen(acpi_param) == 0) && acpi_disabled )
+        {
+            printk("ACPI is disabled, notifying Domain 0 (acpi=off)\n");
+            safe_strcpy(acpi_param, "off");
+        }
+        if ( (strlen(acpi_param) != 0) && !strstr(dom0_cmdline, "acpi=") )
+        {
+            safe_strcat(dom0_cmdline, " acpi=");
+            safe_strcat(dom0_cmdline, acpi_param);
+        }
+
+        cmdline = dom0_cmdline;
+    }
+
+    /*
+     * Temporarily clear SMAP in CR4 to allow user-accesses in construct_dom0().
+     * This saves a large number of corner cases interactions with
+     * copy_from_user().
+     */
+    if ( cpu_has_smap )
+    {
+        cr4_pv32_mask &= ~X86_CR4_SMAP;
+        write_cr4(read_cr4() & ~X86_CR4_SMAP);
+    }
+
+    if ( construct_dom0(d, image, headroom, initrd, cmdline) != 0 )
+        panic("Could not construct domain 0\n");
+
+    if ( cpu_has_smap )
+    {
+        write_cr4(read_cr4() | X86_CR4_SMAP);
+        cr4_pv32_mask |= X86_CR4_SMAP;
+    }
+
+    return d;
+}
+
 /* How much of the directmap is prebuilt at compile time. */
 #define PREBUILT_MAP_LIMIT (1 << L2_PAGETABLE_SHIFT)
 
@@ -697,12 +783,6 @@ void __init noreturn __start_xen(unsigned long mbi_p)
         .parity    = 'n',
         .stop_bits = 1
     };
-    struct xen_domctl_createdomain dom0_cfg = {
-        .flags = IS_ENABLED(CONFIG_TBOOT) ? XEN_DOMCTL_CDF_s3_integrity : 0,
-        .max_evtchn_port = -1,
-        .max_grant_frames = -1,
-        .max_maptrack_frames = -1,
-    };
     const char *hypervisor_name;
 
     /* Critical region without IDT or TSS.  Any fault is deadly! */
@@ -1740,58 +1820,13 @@ void __init noreturn __start_xen(unsigned long mbi_p)
     init_guest_cpuid();
     init_guest_msr_policy();
 
-    if ( opt_dom0_pvh )
-    {
-        dom0_cfg.flags |= (XEN_DOMCTL_CDF_hvm |
-                           ((hvm_hap_supported() && !opt_dom0_shadow) ?
-                            XEN_DOMCTL_CDF_hap : 0));
-
-        dom0_cfg.arch.emulation_flags |=
-            XEN_X86_EMU_LAPIC | XEN_X86_EMU_IOAPIC | XEN_X86_EMU_VPCI;
-    }
-    dom0_cfg.max_vcpus = dom0_max_vcpus();
-
-    if ( iommu_enabled )
-        dom0_cfg.flags |= XEN_DOMCTL_CDF_iommu;
-
-    /* Create initial domain 0. */
-    dom0 = domain_create(get_initial_domain_id(), &dom0_cfg, !pv_shim);
-    if ( IS_ERR(dom0) || (alloc_dom0_vcpu0(dom0) == NULL) )
-        panic("Error creating domain 0\n");
-
-    /* Grab the DOM0 command line. */
-    cmdline = (char *)(mod[0].string ? __va(mod[0].string) : NULL);
-    if ( (cmdline != NULL) || (kextra != NULL) )
-    {
-        static char __initdata dom0_cmdline[MAX_GUEST_CMDLINE];
-
-        cmdline = cmdline_cook(cmdline, loader);
-        safe_strcpy(dom0_cmdline, cmdline);
-
-        if ( kextra != NULL )
-            /* kextra always includes exactly one leading space. */
-            safe_strcat(dom0_cmdline, kextra);
-
-        /* Append any extra parameters. */
-        if ( skip_ioapic_setup && !strstr(dom0_cmdline, "noapic") )
-            safe_strcat(dom0_cmdline, " noapic");
-        if ( (strlen(acpi_param) == 0) && acpi_disabled )
-        {
-            printk("ACPI is disabled, notifying Domain 0 (acpi=off)\n");
-            safe_strcpy(acpi_param, "off");
-        }
-        if ( (strlen(acpi_param) != 0) && !strstr(dom0_cmdline, "acpi=") )
-        {
-            safe_strcat(dom0_cmdline, " acpi=");
-            safe_strcat(dom0_cmdline, acpi_param);
-        }
-
-        cmdline = dom0_cmdline;
-    }
-
     if ( xen_cpuidle )
         xen_processor_pmbits |= XEN_PROCESSOR_PM_CX;
 
+    printk("%sNX (Execute Disable) protection %sactive\n",
+           cpu_has_nx ? XENLOG_INFO : XENLOG_WARNING "Warning: ",
+           cpu_has_nx ? "" : "not ");
+
     initrdidx = find_first_bit(module_map, mbi->mods_count);
     if ( initrdidx < mbi->mods_count )
         initrd = mod + initrdidx;
@@ -1801,34 +1836,14 @@ void __init noreturn __start_xen(unsigned long mbi_p)
                "Multiple initrd candidates, picking module #%u\n",
                initrdidx);
 
-    /*
-     * Temporarily clear SMAP in CR4 to allow user-accesses in construct_dom0().
-     * This saves a large number of corner cases interactions with
-     * copy_from_user().
-     */
-    if ( cpu_has_smap )
-    {
-        cr4_pv32_mask &= ~X86_CR4_SMAP;
-        write_cr4(read_cr4() & ~X86_CR4_SMAP);
-    }
-
-    printk("%sNX (Execute Disable) protection %sactive\n",
-           cpu_has_nx ? XENLOG_INFO : XENLOG_WARNING "Warning: ",
-           cpu_has_nx ? "" : "not ");
-
     /*
      * We're going to setup domain0 using the module(s) that we stashed safely
      * above our heap. The second module, if present, is an initrd ramdisk.
      */
-    if ( construct_dom0(dom0, mod, modules_headroom, initrd, cmdline) != 0 )
+    dom0 = create_dom0(mod, modules_headroom, initrd, kextra, loader);
+    if ( dom0 == NULL )
         panic("Could not set up DOM0 guest OS\n");
 
-    if ( cpu_has_smap )
-    {
-        write_cr4(read_cr4() | X86_CR4_SMAP);
-        cr4_pv32_mask |= X86_CR4_SMAP;
-    }
-
     heap_init_late();
 
     init_trace_bufs();
-- 
2.21.0


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