[PATCH v3 4/9] x86/PVH: provide VGA console info to Dom0

[Jan Beulich <jbeulich@xxxxxxxx>]

Like PV Dom0 in order to use the console if in a mode other than text
80x25 the kernel needs to be provided information about this mode. Bump
HVM start info's "current" version to 2 and use a previously reserved
32-bit field to provide struct dom0_vga_console_info's position and
size.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
v3: New.

--- a/xen/arch/x86/hvm/dom0_build.c
+++ b/xen/arch/x86/hvm/dom0_build.c
@@ -19,6 +19,7 @@
  */
 
 #include <xen/acpi.h>
+#include <xen/console.h>
 #include <xen/init.h>
 #include <xen/libelf.h>
 #include <xen/multiboot.h>
@@ -549,6 +550,11 @@ static int __init pvh_load_kernel(struct
     paddr_t last_addr;
     struct hvm_start_info start_info = { 0 };
     struct hvm_modlist_entry mod = { 0 };
+#ifdef CONFIG_VIDEO
+    struct dom0_vga_console_info vga_info = { 0 };
+#else
+    struct {} __maybe_unused vga_info;
+#endif
     struct vcpu *v = d->vcpu[0];
     int rc;
 
@@ -598,7 +604,7 @@ static int __init pvh_load_kernel(struct
      * split into smaller allocations, done as a single region in order to
      * simplify it.
      */
-    last_addr = find_memory(d, &elf, sizeof(start_info) +
+    last_addr = find_memory(d, &elf, sizeof(start_info) + sizeof(vga_info) +
                             (initrd ? ROUNDUP(initrd->mod_end, PAGE_SIZE) +
                                       sizeof(mod)
                                     : 0) +
@@ -672,6 +678,22 @@ static int __init pvh_load_kernel(struct
         last_addr += sizeof(mod);
     }
 
+#ifdef CONFIG_VIDEO
+    if ( fill_console_start_info(&vga_info) )
+    {
+        rc = hvm_copy_to_guest_phys(last_addr + sizeof(start_info),
+                                    &vga_info, sizeof(vga_info), v);
+        if ( !rc )
+        {
+            start_info.version = 2;
+            start_info.vga_info.offset = sizeof(start_info);
+            start_info.vga_info.size = sizeof(vga_info);
+        }
+        else
+            printk("Unable to copy VGA info to guest\n");
+    }
+#endif
+
     start_info.magic = XEN_HVM_START_MAGIC_VALUE;
     start_info.flags = SIF_PRIVILEGED | SIF_INITDOMAIN;
     rc = hvm_copy_to_guest_phys(last_addr, &start_info, sizeof(start_info), v);
--- a/xen/include/public/arch-x86/hvm/start_info.h
+++ b/xen/include/public/arch-x86/hvm/start_info.h
@@ -33,7 +33,7 @@
  *    | magic          | Contains the magic value XEN_HVM_START_MAGIC_VALUE
  *    |                | ("xEn3" with the 0x80 bit of the "E" set).
  *  4 +----------------+
- *    | version        | Version of this structure. Current version is 1. New
+ *    | version        | Version of this structure. Current version is 2. New
  *    |                | versions are guaranteed to be backwards-compatible.
  *  8 +----------------+
  *    | flags          | SIF_xxx flags.
@@ -55,7 +55,15 @@
  *    |                | if there is no memory map being provided. Only
  *    |                | present in version 1 and newer of the structure.
  * 52 +----------------+
- *    | reserved       | Version 1 and newer only.
+ *    | vga_info.offset| Offset of struct dom0_vga_console_info from base of
+ *    |                | struct hvm_start_info. Optional and only present in
+ *    |                | version 2 and newer of the structure when
+ *    |                | SIF_INITDOMAIN is set; zero if absent.
+ * 54 +----------------+
+ *    | vga_info.size  | Size of present parts of struct dom0_vga_console_info.
+ *    |                | Optional and only present in version 2 and newer of
+ *    |                | the structure when SIF_INITDOMAIN is set; zero if
+ *    |                | absent.
  * 56 +----------------+
  *
  * The layout of each entry in the module structure is the following:
@@ -139,7 +147,15 @@ struct hvm_start_info {
     uint32_t memmap_entries;    /* Number of entries in the memmap table.    */
                                 /* Value will be zero if there is no memory  */
                                 /* map being provided.                       */
-    uint32_t reserved;          /* Must be zero.                             */
+    /*
+     * The following sub-structure is only present in version 2 and newer
+     * when SIF_INITDOMAIN is set. It is reserved in version 1 or when
+     * SIF_INITDOMAIN is clear, and absent in version 0.
+     */
+    struct {                    /* Coord-s of struct dom0_vga_console_info.  */
+        uint16_t offset;        /* ... from base of struct hvm_start_info.   */
+        uint16_t size;          /* ... of present parts of the struct.       */
+    } vga_info;
 };
 
 struct hvm_modlist_entry {