libxc/xen: introduce a start info structure for HVMlite guests

This structure contains the physical address of the command line, as well as
the physical address of the list of loaded modules. The physical address of
this structure is passed to the guest at boot time in the %ebx register.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>

tools/libxc/xc_dom_x86.c

@@ -633,7 +633,70 @@ static int alloc_magic_pages_hvm(struct xc_dom_image *dom)
     xc_hvm_param_set(xch, domid, HVM_PARAM_SHARING_RING_PFN,
                      special_pfn(SPECIALPAGE_SHARING));
 
-    if ( dom->device_model )
+    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);
+
+        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. */
+
+        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);
+        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 )
+        {
+            strncpy(cmdline, dom->cmdline, MAX_GUEST_CMDLINE);
+            cmdline[MAX_GUEST_CMDLINE - 1] = '\0';
+            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
     {
         /*
          * Allocate and clear additional ioreq server pages. The default
@@ -1032,6 +1095,9 @@ static int vcpu_hvm(struct xc_dom_image *dom)
     /* Set the IP. */
     bsp_ctx.cpu.rip = dom->parms.phys_entry;
 
+    if ( dom->start_info_pfn )
+        bsp_ctx.cpu.rbx = dom->start_info_pfn << PAGE_SHIFT;
+
     /* Set the end descriptor. */
     bsp_ctx.end_d.typecode = HVM_SAVE_CODE(END);
     bsp_ctx.end_d.instance = 0;

xen/include/public/xen.h

@@ -784,6 +784,29 @@ struct start_info {
 };
 typedef struct start_info start_info_t;
 
+/*
+ * Start of day structure passed to PVH guests in %ebx.
+ *
+ * NOTE: nothing will be loaded at physical address 0, so
+ * a 0 value in any of the address fields should be treated
+ * as not present.
+ */
+struct hvm_start_info {
+#define HVM_START_MAGIC_VALUE 0x336ec578
+    uint32_t magic;             /* Contains the magic value 0x336ec578       */
+                                /* ("xEn3" with the 0x80 bit of the "E" set).*/
+    uint32_t flags;             /* SIF_xxx flags.                            */
+    uint32_t cmdline_paddr;     /* Physical address of the command line.     */
+    uint32_t nr_modules;        /* Number of modules passed to the kernel.   */
+    uint32_t modlist_paddr;     /* Physical address of an array of           */
+                                /* hvm_modlist_entry.                        */
+};
+
+struct hvm_modlist_entry {
+    uint32_t paddr;             /* Physical address of the module.           */
+    uint32_t size;              /* Size of the module in bytes.              */
+};
+
 /* New console union for dom0 introduced in 0x00030203. */
 #if __XEN_INTERFACE_VERSION__ < 0x00030203
 #define console_mfn    console.domU.mfn