[Xen-devel] [PATCH] libxc: Defer initialization of start_page for HVM guests

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

With commit 8c45adec18e0 ("libxc: create unmapped initrd in domain
builder if supported") location of ramdisk may not be available to
HVMlite guests by the time alloc_magic_pages_hvm() is invoked if the
guest supports unmapped initrd.

Since the only operation related to allocating magic pages in that
routine is allocation of HVMlite start info we can move everything
else to a later point such as xc_dom_arch.start_info().

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
---
I am not sure xc_dom_arch.start_info() is the right place neither since we
still are doing things that have nothing to do with start_info.

 tools/libxc/xc_dom_x86.c |   45 ++++++++++++++++++++++++++++++---------------
 1 files changed, 30 insertions(+), 15 deletions(-)

diff --git a/tools/libxc/xc_dom_x86.c b/tools/libxc/xc_dom_x86.c
index 3960875..f64079e 100644
--- a/tools/libxc/xc_dom_x86.c
+++ b/tools/libxc/xc_dom_x86.c
@@ -585,6 +585,32 @@ static void build_hvm_info(void *hvm_info_page, struct 
xc_dom_image *dom)
 
 static int alloc_magic_pages_hvm(struct xc_dom_image *dom)
 {
+        struct xc_dom_seg seg;
+        size_t start_info_size = sizeof(struct hvm_start_info);
+
+        if ( dom->device_model )
+            return 0;
+
+        if ( dom->cmdline )
+            start_info_size += ROUNDUP(strlen(dom->cmdline) + 1, 8);
+        if ( dom->ramdisk_blob )
+            /* Limited to one module. */
+            start_info_size += sizeof( struct hvm_modlist_entry);
+
+        if ( xc_dom_alloc_segment(dom, &seg, "HVMlite start info", 0,
+                                  start_info_size) )
+        {
+            DOMPRINTF("Unable to reserve memory for the start info");
+            return -1;
+        }
+
+        dom->start_info_pfn = seg.pfn;
+
+        return 0;
+}
+
+static int start_info_hvm(struct xc_dom_image *dom)
+{
     unsigned long i;
     void *hvm_info_page;
     uint32_t *ident_pt, domid = dom->guest_domid;
@@ -636,7 +662,6 @@ static int alloc_magic_pages_hvm(struct xc_dom_image *dom)
 
     if ( !dom->device_model )
     {
-        struct xc_dom_seg seg;
         struct hvm_start_info *start_info;
         char *cmdline;
         struct hvm_modlist_entry *modlist;
@@ -653,17 +678,9 @@ static int alloc_magic_pages_hvm(struct xc_dom_image *dom)
         if ( dom->ramdisk_blob )
             start_info_size += sizeof(*modlist); /* Limited to one module. */
 
-        rc = xc_dom_alloc_segment(dom, &seg, "HVMlite start info", 0,
-                                  start_info_size);
-        if ( rc != 0 )
-        {
-            DOMPRINTF("Unable to reserve memory for the start info");
-            goto out;
-        }
-
         start_page = xc_map_foreign_range(xch, domid, start_info_size,
                                           PROT_READ | PROT_WRITE,
-                                          seg.pfn);
+                                          dom->start_info_pfn);
         if ( start_page == NULL )
         {
             DOMPRINTF("Unable to map HVM start info page");
@@ -678,7 +695,7 @@ static int alloc_magic_pages_hvm(struct xc_dom_image *dom)
         {
             strncpy(cmdline, dom->cmdline, MAX_GUEST_CMDLINE);
             cmdline[MAX_GUEST_CMDLINE - 1] = '\0';
-            start_info->cmdline_paddr = (seg.pfn << PAGE_SHIFT) +
+            start_info->cmdline_paddr = (dom->start_info_pfn << PAGE_SHIFT) +
                                 ((uintptr_t)cmdline - (uintptr_t)start_info);
         }
 
@@ -686,7 +703,7 @@ static int alloc_magic_pages_hvm(struct xc_dom_image *dom)
         {
             modlist[0].paddr = dom->ramdisk_seg.vstart - dom->parms.virt_base;
             modlist[0].size = dom->ramdisk_seg.vend - dom->ramdisk_seg.vstart;
-            start_info->modlist_paddr = (seg.pfn << PAGE_SHIFT) +
+            start_info->modlist_paddr = (dom->start_info_pfn << PAGE_SHIFT) +
                                 ((uintptr_t)modlist - (uintptr_t)start_info);
             start_info->nr_modules = 1;
         }
@@ -694,8 +711,6 @@ static int alloc_magic_pages_hvm(struct xc_dom_image *dom)
         start_info->magic = HVM_START_MAGIC_VALUE;
 
         munmap(start_page, start_info_size);
-
-        dom->start_info_pfn = seg.pfn;
     }
     else
     {
@@ -1845,7 +1860,7 @@ static struct xc_dom_arch xc_hvm_32 = {
     .alloc_magic_pages = alloc_magic_pages_hvm,
     .alloc_pgtables = alloc_pgtables_hvm,
     .setup_pgtables = NULL,
-    .start_info = NULL,
+    .start_info = start_info_hvm,
     .shared_info = NULL,
     .vcpu = vcpu_hvm,
     .meminit = meminit_hvm,
-- 
1.7.1


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