With MB2 the boot loader may provide this information, allowing us to
obtain it without needing to enter real mode (assuming we don't need to
set a new mode from "vga=", but can instead inherit the one the
bootloader may have established).

Signed-off-by: Jan Beulich <jbeulich@suse.com>
---
v2: New.

--- a/xen/arch/x86/boot/Makefile
+++ b/xen/arch/x86/boot/Makefile
@@ -4,7 +4,7 @@ DEFS_H_DEPS = defs.h $(BASEDIR)/include/
 
 CMDLINE_DEPS = $(DEFS_H_DEPS) video.h
 
-RELOC_DEPS = $(DEFS_H_DEPS) \
+RELOC_DEPS = $(DEFS_H_DEPS) video.h \
 	     $(BASEDIR)/include/generated/autoconf.h \
 	     $(BASEDIR)/include/xen/kconfig.h \
 	     $(BASEDIR)/include/xen/multiboot.h \
--- a/xen/arch/x86/boot/defs.h
+++ b/xen/arch/x86/boot/defs.h
@@ -53,6 +53,7 @@ typedef unsigned int u32;
 typedef unsigned long long u64;
 typedef unsigned int size_t;
 typedef u8 uint8_t;
+typedef u16 uint16_t;
 typedef u32 uint32_t;
 typedef u64 uint64_t;
 
--- a/xen/arch/x86/boot/head.S
+++ b/xen/arch/x86/boot/head.S
@@ -562,12 +562,18 @@ trampoline_setup:
         mov     %esi, sym_esi(xen_phys_start)
         mov     %esi, sym_esi(trampoline_xen_phys_start)
 
-        mov     sym_esi(trampoline_phys), %ecx
-
         /* Get bottom-most low-memory stack address. */
+        mov     sym_esi(trampoline_phys), %ecx
         add     $TRAMPOLINE_SPACE,%ecx
 
+#ifdef CONFIG_VIDEO
+        lea     sym_esi(boot_vid_info), %edx
+#else
+        xor     %edx, %edx
+#endif
+
         /* Save Multiboot / PVH info struct (after relocation) for later use. */
+        push    %edx                /* Boot video info to be filled from MB2. */
         push    %ecx                /* Bottom-most low-memory stack address. */
         push    %ebx                /* Multiboot / PVH information address. */
         push    %eax                /* Magic number. */
--- a/xen/arch/x86/boot/reloc.c
+++ b/xen/arch/x86/boot/reloc.c
@@ -14,9 +14,10 @@
 
 /*
  * This entry point is entered from xen/arch/x86/boot/head.S with:
- *   - 0x4(%esp) = MAGIC,
- *   - 0x8(%esp) = INFORMATION_ADDRESS,
- *   - 0xc(%esp) = TOPMOST_LOW_MEMORY_STACK_ADDRESS.
+ *   - 0x04(%esp) = MAGIC,
+ *   - 0x08(%esp) = INFORMATION_ADDRESS,
+ *   - 0x0c(%esp) = TOPMOST_LOW_MEMORY_STACK_ADDRESS.
+ *   - 0x10(%esp) = BOOT_VIDEO_INFO_ADDRESS.
  */
 asm (
     "    .text                         \n"
@@ -32,6 +33,39 @@ asm (
 #include "../../../include/xen/kconfig.h"
 #include <public/arch-x86/hvm/start_info.h>
 
+#ifdef CONFIG_VIDEO
+# include "video.h"
+
+/* VESA control information */
+struct __packed vesa_ctrl_info {
+    uint8_t signature[4];
+    uint16_t version;
+    uint32_t oem_name;
+    uint32_t capabilities;
+    uint32_t mode_list;
+    uint16_t mem_size;
+    /* We don't use any further fields. */
+};
+
+/* VESA 2.0 mode information */
+struct vesa_mode_info {
+    uint16_t attrib;
+    uint8_t window[14]; /* We don't use the individual fields. */
+    uint16_t bytes_per_line;
+    uint16_t width;
+    uint16_t height;
+    uint8_t cell_width;
+    uint8_t cell_height;
+    uint8_t nr_planes;
+    uint8_t depth;
+    uint8_t memory[5]; /* We don't use the individual fields. */
+    struct boot_video_colors colors;
+    uint8_t direct_color;
+    uint32_t base;
+    /* We don't use any further fields. */
+};
+#endif /* CONFIG_VIDEO */
+
 #define get_mb2_data(tag, type, member)   (((multiboot2_tag_##type##_t *)(tag))->member)
 #define get_mb2_string(tag, type, member) ((u32)get_mb2_data(tag, type, member))
 
@@ -146,7 +180,7 @@ static multiboot_info_t *mbi_reloc(u32 m
     return mbi_out;
 }
 
-static multiboot_info_t *mbi2_reloc(u32 mbi_in)
+static multiboot_info_t *mbi2_reloc(uint32_t mbi_in, uint32_t video_out)
 {
     const multiboot2_fixed_t *mbi_fix = _p(mbi_in);
     const multiboot2_memory_map_t *mmap_src;
@@ -154,6 +188,9 @@ static multiboot_info_t *mbi2_reloc(u32
     module_t *mbi_out_mods = NULL;
     memory_map_t *mmap_dst;
     multiboot_info_t *mbi_out;
+#ifdef CONFIG_VIDEO
+    struct boot_video_info *video = NULL;
+#endif
     u32 ptr;
     unsigned int i, mod_idx = 0;
 
@@ -254,17 +291,64 @@ static multiboot_info_t *mbi2_reloc(u32
             ++mod_idx;
             break;
 
+#ifdef CONFIG_VIDEO
+        case MULTIBOOT2_TAG_TYPE_VBE:
+            if ( video_out )
+            {
+                const struct vesa_ctrl_info *ci;
+                const struct vesa_mode_info *mi;
+
+                video = _p(video_out);
+                ci = (void *)get_mb2_data(tag, vbe, vbe_control_info);
+                mi = (void *)get_mb2_data(tag, vbe, vbe_mode_info);
+
+                if ( ci->version >= 0x0200 && (mi->attrib & 0x9b) == 0x9b )
+                {
+                    video->capabilities = ci->capabilities;
+                    video->lfb_linelength = mi->bytes_per_line;
+                    video->lfb_width = mi->width;
+                    video->lfb_height = mi->height;
+                    video->lfb_depth = mi->depth;
+                    video->lfb_base = mi->base;
+                    video->lfb_size = ci->mem_size;
+                    video->colors = mi->colors;
+                    video->vesa_attrib = mi->attrib;
+                }
+
+                video->vesapm.seg = get_mb2_data(tag, vbe, vbe_interface_seg);
+                video->vesapm.off = get_mb2_data(tag, vbe, vbe_interface_off);
+            }
+            break;
+
+        case MULTIBOOT2_TAG_TYPE_FRAMEBUFFER:
+            if ( (get_mb2_data(tag, framebuffer, framebuffer_type) !=
+                  MULTIBOOT2_FRAMEBUFFER_TYPE_RGB) )
+            {
+                video_out = 0;
+                video = NULL;
+            }
+            break;
+#endif /* CONFIG_VIDEO */
+
         case MULTIBOOT2_TAG_TYPE_END:
-            return mbi_out;
+            goto end; /* Cannot "break;" here. */
 
         default:
             break;
         }
 
+ end:
+
+#ifdef CONFIG_VIDEO
+    if ( video )
+        video->orig_video_isVGA = 0x23;
+#endif
+
     return mbi_out;
 }
 
-void * __stdcall reloc(u32 magic, u32 in, u32 trampoline)
+void *__stdcall reloc(uint32_t magic, uint32_t in, uint32_t trampoline,
+                      uint32_t video_info)
 {
     alloc = trampoline;
 
@@ -274,7 +358,7 @@ void * __stdcall reloc(u32 magic, u32 in
         return mbi_reloc(in);
 
     case MULTIBOOT2_BOOTLOADER_MAGIC:
-        return mbi2_reloc(in);
+        return mbi2_reloc(in, video_info);
 
     case XEN_HVM_START_MAGIC_VALUE:
         if ( IS_ENABLED(CONFIG_PVH_GUEST) )
--- a/xen/arch/x86/boot/video.h
+++ b/xen/arch/x86/boot/video.h
@@ -28,4 +28,45 @@
 /* The "recalculate timings" flag */
 #define VIDEO_RECALC        0x8000
 
+#ifndef __ASSEMBLY__
+struct boot_video_info {
+    uint8_t  orig_x;             /* 0x00 */
+    uint8_t  orig_y;             /* 0x01 */
+    uint8_t  orig_video_mode;    /* 0x02 */
+    uint8_t  orig_video_cols;    /* 0x03 */
+    uint8_t  orig_video_lines;   /* 0x04 */
+    uint8_t  orig_video_isVGA;   /* 0x05 */
+    uint16_t orig_video_points;  /* 0x06 */
+
+    /* VESA graphic mode -- linear frame buffer */
+    uint32_t capabilities;       /* 0x08 */
+    uint16_t lfb_linelength;     /* 0x0c */
+    uint16_t lfb_width;          /* 0x0e */
+    uint16_t lfb_height;         /* 0x10 */
+    uint16_t lfb_depth;          /* 0x12 */
+    uint32_t lfb_base;           /* 0x14 */
+    uint32_t lfb_size;           /* 0x18 */
+    union {
+        struct {
+            uint8_t  red_size;   /* 0x1c */
+            uint8_t  red_pos;    /* 0x1d */
+            uint8_t  green_size; /* 0x1e */
+            uint8_t  green_pos;  /* 0x1f */
+            uint8_t  blue_size;  /* 0x20 */
+            uint8_t  blue_pos;   /* 0x21 */
+            uint8_t  rsvd_size;  /* 0x22 */
+            uint8_t  rsvd_pos;   /* 0x23 */
+        };
+        struct boot_video_colors {
+            uint8_t  rgbr[8];
+        } colors;
+    };
+    struct {
+        uint16_t seg;            /* 0x24 */
+        uint16_t off;            /* 0x26 */
+    } vesapm;
+    uint16_t vesa_attrib;        /* 0x28 */
+};
+#endif /* __ASSEMBLY__ */
+
 #endif /* __BOOT_VIDEO_H__ */
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -515,35 +515,7 @@ static void __init setup_max_pdx(unsigne
 static struct e820map __initdata boot_e820;
 
 #ifdef CONFIG_VIDEO
-struct boot_video_info {
-    u8  orig_x;             /* 0x00 */
-    u8  orig_y;             /* 0x01 */
-    u8  orig_video_mode;    /* 0x02 */
-    u8  orig_video_cols;    /* 0x03 */
-    u8  orig_video_lines;   /* 0x04 */
-    u8  orig_video_isVGA;   /* 0x05 */
-    u16 orig_video_points;  /* 0x06 */
-
-    /* VESA graphic mode -- linear frame buffer */
-    u32 capabilities;       /* 0x08 */
-    u16 lfb_linelength;     /* 0x0c */
-    u16 lfb_width;          /* 0x0e */
-    u16 lfb_height;         /* 0x10 */
-    u16 lfb_depth;          /* 0x12 */
-    u32 lfb_base;           /* 0x14 */
-    u32 lfb_size;           /* 0x18 */
-    u8  red_size;           /* 0x1c */
-    u8  red_pos;            /* 0x1d */
-    u8  green_size;         /* 0x1e */
-    u8  green_pos;          /* 0x1f */
-    u8  blue_size;          /* 0x20 */
-    u8  blue_pos;           /* 0x21 */
-    u8  rsvd_size;          /* 0x22 */
-    u8  rsvd_pos;           /* 0x23 */
-    u16 vesapm_seg;         /* 0x24 */
-    u16 vesapm_off;         /* 0x26 */
-    u16 vesa_attrib;        /* 0x28 */
-};
+# include "boot/video.h"
 extern struct boot_video_info boot_vid_info;
 #endif
 
--- a/xen/include/xen/multiboot2.h
+++ b/xen/include/xen/multiboot2.h
@@ -158,6 +158,59 @@ typedef struct {
     multiboot2_memory_map_t entries[];
 } multiboot2_tag_mmap_t;
 
+typedef struct
+{
+    uint32_t type;
+    uint32_t size;
+    uint16_t vbe_mode;
+    uint16_t vbe_interface_seg;
+    uint16_t vbe_interface_off;
+    uint16_t vbe_interface_len;
+    uint8_t vbe_control_info[512];
+    uint8_t vbe_mode_info[256];
+} multiboot2_tag_vbe_t;
+
+typedef struct
+{
+    uint8_t red;
+    uint8_t green;
+    uint8_t blue;
+} multiboot2_color_t;
+
+typedef struct
+{
+    uint32_t type;
+    uint32_t size;
+    uint64_t framebuffer_addr;
+    uint32_t framebuffer_pitch;
+    uint32_t framebuffer_width;
+    uint32_t framebuffer_height;
+    uint8_t framebuffer_bpp;
+#define MULTIBOOT2_FRAMEBUFFER_TYPE_INDEXED  0
+#define MULTIBOOT2_FRAMEBUFFER_TYPE_RGB      1
+#define MULTIBOOT2_FRAMEBUFFER_TYPE_EGA_TEXT 2
+    uint8_t framebuffer_type;
+    uint16_t reserved;
+
+    union
+    {
+        struct
+        {
+            uint16_t framebuffer_palette_num_colors;
+            multiboot2_color_t framebuffer_palette[];
+        };
+        struct
+        {
+            uint8_t framebuffer_red_field_position;
+            uint8_t framebuffer_red_mask_size;
+            uint8_t framebuffer_green_field_position;
+            uint8_t framebuffer_green_mask_size;
+            uint8_t framebuffer_blue_field_position;
+            uint8_t framebuffer_blue_mask_size;
+        };
+    };
+} multiboot2_tag_framebuffer_t;
+
 typedef struct {
     u32 type;
     u32 size;