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Re: [Xen-devel] [PATCH RFC 09/15] xen/arm: refactor construct_dom0



Hi Stefano,

On 13/06/18 23:15, Stefano Stabellini wrote:
Move generic initializations out of construct_dom0 so that they can be
reused.

No functional changes in this patch.

Signed-off-by: Stefano Stabellini <stefanos@xxxxxxxxxx>
---
  xen/arch/arm/domain_build.c | 124 ++++++++++++++++++++++++--------------------
  1 file changed, 67 insertions(+), 57 deletions(-)

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 4e4cd19..b31c563 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -2092,73 +2092,27 @@ static void __init find_gnttab_region(struct domain *d,
             kinfo->gnttab_start, kinfo->gnttab_start + kinfo->gnttab_size);
  }
-int __init construct_dom0(struct domain *d)
+int __init __construct_domain(struct domain *d, struct kernel_info *kinfo)
  {
-    struct kernel_info kinfo = {};
      struct vcpu *saved_current;
-    int rc, i, cpu;
+    int i, cpu;
struct vcpu *v = d->vcpu[0];
      struct cpu_user_regs *regs = &v->arch.cpu_info->guest_cpu_user_regs;
- /* Sanity! */
-    BUG_ON(d->domain_id != 0);
-    BUG_ON(d->vcpu[0] == NULL);
-    BUG_ON(v->is_initialised);

I think we want to keep the last two BUG_ON here. "d->vcpu[0] == NULL" is making sure that the value used when setting current is sane.

"v->is_initalised" is making sure this function is not called twice by mistake. Indeed the variable will be set at the end of __construct_domain.

-
-    printk("*** LOADING DOMAIN 0 ***\n");
-    if ( dom0_mem <= 0 )
-    {
-        warning_add("PLEASE SPECIFY dom0_mem PARAMETER - USING 512M FOR 
NOW\n");
-        dom0_mem = MB(512);
-    }
-
-
-    iommu_hwdom_init(d);
-
-    d->max_pages = ~0U;
-
-    kinfo.unassigned_mem = dom0_mem;
-    kinfo.d = d;
-
-    rc = kernel_probe(&kinfo);
-    if ( rc < 0 )
-        return rc;
-
  #ifdef CONFIG_ARM_64
      /* if aarch32 mode is not supported at EL1 do not allow 32-bit domain */
-    if ( !(cpu_has_el1_32) && kinfo.type == DOMAIN_32BIT )
+    if ( !(cpu_has_el1_32) && kinfo->type == DOMAIN_32BIT )
      {
          printk("Platform does not support 32-bit domain\n");
          return -EINVAL;
      }
-    d->arch.type = kinfo.type;

Any reason to move this out?

if ( is_64bit_domain(d) )
          vcpu_switch_to_aarch64_mode(v);
#endif - allocate_memory(d, &kinfo);

I think this could stay here.

-    find_gnttab_region(d, &kinfo);
-
-    /* Map extra GIC MMIO, irqs and other hw stuffs to dom0. */
-    rc = gic_map_hwdom_extra_mappings(d);
-    if ( rc < 0 )
-        return rc;
-
-    rc = platform_specific_mapping(d);
-    if ( rc < 0 )
-        return rc;
-
-    if ( acpi_disabled )
-        rc = prepare_dtb(d, &kinfo);
-    else
-        rc = prepare_acpi(d, &kinfo);

I think this is probably a call to add "hwdom" in the name of the 2 functions.

-
-    if ( rc < 0 )
-        return rc;
-
      /*
       * The following loads use the domain's p2m and require current to
       * be a vcpu of the domain, temporarily switch
@@ -2171,20 +2125,18 @@ int __init construct_dom0(struct domain *d)
       * kernel_load will determine the placement of the kernel as well
       * as the initrd & fdt in RAM, so call it first.
       */
-    kernel_load(&kinfo);
+    kernel_load(kinfo);
      /* initrd_load will fix up the fdt, so call it before dtb_load */
-    initrd_load(&kinfo);
-    dtb_load(&kinfo);
+    initrd_load(kinfo);
+    dtb_load(kinfo);
/* Now that we are done restore the original p2m and current. */
      set_current(saved_current);
      p2m_restore_state(saved_current);
- discard_initial_modules();
-
      memset(regs, 0, sizeof(*regs));
- regs->pc = (register_t)kinfo.entry;
+    regs->pc = (register_t)kinfo->entry;
if ( is_32bit_domain(d) )
      {
@@ -2202,14 +2154,14 @@ int __init construct_dom0(struct domain *d)
           */
          regs->r0 = 0; /* SBZ */
          regs->r1 = 0xffffffff; /* We use DTB therefore no machine id */
-        regs->r2 = kinfo.dtb_paddr;
+        regs->r2 = kinfo->dtb_paddr;
      }
  #ifdef CONFIG_ARM_64
      else
      {
          regs->cpsr = PSR_GUEST64_INIT;
          /* From linux/Documentation/arm64/booting.txt */
-        regs->x0 = kinfo.dtb_paddr;
+        regs->x0 = kinfo->dtb_paddr;
          regs->x1 = 0; /* Reserved for future use */
          regs->x2 = 0; /* Reserved for future use */
          regs->x3 = 0; /* Reserved for future use */
@@ -2235,6 +2187,64 @@ int __init construct_dom0(struct domain *d)
      return 0;
  }
+int __init construct_dom0(struct domain *d)
+{
+    struct kernel_info kinfo = {};
+    int rc;
+
+    struct vcpu *v = d->vcpu[0];
+
+    /* Sanity! */
+    BUG_ON(d->domain_id != 0);
+    BUG_ON(d->vcpu[0] == NULL);
+    BUG_ON(v->is_initialised);
+
+    printk("*** LOADING DOMAIN 0 ***\n");
+    if ( dom0_mem <= 0 )
+    {
+        warning_add("PLEASE SPECIFY dom0_mem PARAMETER - USING 512M FOR 
NOW\n");
+        dom0_mem = MB(512);
+    }
+
+

No need to copy the second newline :).

+    iommu_hwdom_init(d);
+
+    d->max_pages = ~0U;
+
+    kinfo.unassigned_mem = dom0_mem;
+    kinfo.d = d;
+
+    rc = kernel_probe(&kinfo);
+    if ( rc < 0 )
+        return rc;
+
+    allocate_memory(d, &kinfo);
+    find_gnttab_region(d, &kinfo);
+
+    /* Map extra GIC MMIO, irqs and other hw stuffs to dom0. */
+    rc = gic_map_hwdom_extra_mappings(d);
+    if ( rc < 0 )
+        return rc;
+
+    rc = platform_specific_mapping(d);
+    if ( rc < 0 )
+        return rc;
+
+    d->arch.type = kinfo.type;
+
+    if ( acpi_disabled )
+        rc = prepare_dtb(d, &kinfo);
+    else
+        rc = prepare_acpi(d, &kinfo);
+
+    if ( rc < 0 )
+        return rc;
+
+    discard_initial_modules();

You say "no functional change" in this patch. But this is one. The module are now discard much earlier. This imply that memory baking the Image/Initrd will be free to be re-used at any time.

I don't think this is what we want. Unless you can promise no memory is allocated in __construct_domain().

+
+    return __construct_domain(d, &kinfo);
+}
+
  /*
   * Local variables:
   * mode: C


Cheers,

--
Julien Grall

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