[Xen-devel] [PATCH v2 2/2] 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.

So let's move ramdisk info initialization (along with a few other
operations that are not directly related to allocating magic/special
pages) from alloc_magic_pages_hvm() to bootlate_hvm().

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
---
 tools/libxc/xc_dom_x86.c |  117 ++++++++++++++++++++++++++-------------------
 1 files changed, 68 insertions(+), 49 deletions(-)

diff --git a/tools/libxc/xc_dom_x86.c b/tools/libxc/xc_dom_x86.c
index b696149..e8c947f 100644
--- a/tools/libxc/xc_dom_x86.c
+++ b/tools/libxc/xc_dom_x86.c
@@ -586,23 +586,12 @@ 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)
 {
     unsigned long i;
-    void *hvm_info_page;
     uint32_t *ident_pt, domid = dom->guest_domid;
     int rc;
     xen_pfn_t special_array[X86_HVM_NR_SPECIAL_PAGES];
     xen_pfn_t ioreq_server_array[NR_IOREQ_SERVER_PAGES];
     xc_interface *xch = dom->xch;
 
-    if ( dom->device_model )
-    {
-        if ( (hvm_info_page = xc_map_foreign_range(
-                  xch, domid, PAGE_SIZE, PROT_READ | PROT_WRITE,
-                  HVM_INFO_PFN)) == NULL )
-            goto error_out;
-        build_hvm_info(hvm_info_page, dom);
-        munmap(hvm_info_page, PAGE_SIZE);
-    }
-
     /* Allocate and clear special pages. */
     for ( i = 0; i < X86_HVM_NR_SPECIAL_PAGES; i++ )
         special_array[i] = special_pfn(i);
@@ -637,12 +626,9 @@ 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;
-        void *start_page;
         size_t cmdline_size = 0;
-        size_t start_info_size = sizeof(*start_info);
+        size_t start_info_size = sizeof(struct hvm_start_info);
 
         if ( dom->cmdline )
         {
@@ -666,39 +652,6 @@ static int alloc_magic_pages_hvm(struct xc_dom_image *dom)
             goto out;
         }
 
-        start_page = xc_map_foreign_range(xch, domid, start_info_size,
-                                          PROT_READ | PROT_WRITE,
-                                          seg.pfn);
-        if ( start_page == NULL )
-        {
-            DOMPRINTF("Unable to map HVM start info page");
-            goto error_out;
-        }
-
-        start_info = start_page;
-        cmdline = start_page + sizeof(*start_info);
-        modlist = start_page + sizeof(*start_info) + cmdline_size;
-
-        if ( dom->cmdline )
-        {
-            strcpy(cmdline, dom->cmdline);
-            start_info->cmdline_paddr = (seg.pfn << PAGE_SHIFT) +
-                                ((uintptr_t)cmdline - (uintptr_t)start_info);
-        }
-
-        if ( dom->ramdisk_blob )
-        {
-            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) +
-                                ((uintptr_t)modlist - (uintptr_t)start_info);
-            start_info->nr_modules = 1;
-        }
-
-        start_info->magic = HVM_START_MAGIC_VALUE;
-
-        munmap(start_page, start_info_size);
-
         dom->start_info_pfn = seg.pfn;
     }
     else
@@ -1788,7 +1741,73 @@ static int alloc_pgtables_hvm(struct xc_dom_image *dom)
 
 static int bootlate_hvm(struct xc_dom_image *dom)
 {
-    DOMPRINTF("%s: doing nothing", __func__);
+    uint32_t domid = dom->guest_domid;
+    xc_interface *xch = dom->xch;
+
+    if ( !dom->device_model )
+    {
+        struct hvm_start_info *start_info;
+        size_t start_info_size = sizeof(*start_info);
+        void *start_page;
+        struct hvm_modlist_entry *modlist;
+        size_t cmdline_size = 0;
+
+        if ( dom->cmdline )
+        {
+            cmdline_size = ROUNDUP(strlen(dom->cmdline) + 1, 8);
+            start_info_size += cmdline_size;
+        }
+        if ( dom->ramdisk_blob )
+            start_info_size += sizeof(*modlist); /* Limited to one module. */
+
+        start_page = xc_map_foreign_range(xch, domid, start_info_size,
+                                          PROT_READ | PROT_WRITE,
+                                          dom->start_info_pfn);
+        if ( start_page == NULL )
+        {
+            DOMPRINTF("Unable to map HVM start info page");
+            return -1;
+        }
+
+        start_info = start_page;
+
+        if ( dom->cmdline )
+        {
+            char *cmdline = start_page + sizeof(*start_info);
+
+            /* We've already tested cmdline's size in alloc_magic_pages_hvm() 
*/
+            strcpy(cmdline, dom->cmdline);
+            start_info->cmdline_paddr = (dom->start_info_pfn << PAGE_SHIFT) +
+                                ((uintptr_t)cmdline - (uintptr_t)start_info);
+        }
+
+        if ( dom->ramdisk_blob )
+        {
+            modlist = start_page + sizeof(*start_info) + cmdline_size;
+
+            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 = (dom->start_info_pfn << PAGE_SHIFT) +
+                                ((uintptr_t)modlist - (uintptr_t)start_info);
+            start_info->nr_modules = 1;
+        }
+
+        start_info->magic = HVM_START_MAGIC_VALUE;
+
+        munmap(start_page, start_info_size);
+    }
+    else
+    {
+        void *hvm_info_page;
+
+        if ( (hvm_info_page = xc_map_foreign_range(
+                  xch, domid, PAGE_SIZE, PROT_READ | PROT_WRITE,
+                  HVM_INFO_PFN)) == NULL )
+            return -1;
+        build_hvm_info(hvm_info_page, dom);
+        munmap(hvm_info_page, PAGE_SIZE);
+    }
+
     return 0;
 }
 
-- 
1.7.1


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