[PATCH 2/2] x86: Set up framebuffer given by Multiboot2

[Tu Dinh Ngoc <dinhngoc.tu@xxxxxxx>]

Previously, we do not make use of the framebuffer given by Multiboot.
This means graphics will not work in some scenarios such as booting from
Kexec.

Enable the Multiboot framebuffer if it exists and not overridden by EFI
probe.
---
 xen/arch/x86/setup.c | 45 +++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 42 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 115f8f6517..04d8be407e 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -551,16 +551,55 @@ struct boot_video_info {
 extern struct boot_video_info boot_vid_info;
 #endif
 
-static void __init parse_video_info(void)
+static void __init parse_video_info(multiboot_info_t *mbi)
 {
 #ifdef CONFIG_VIDEO
     struct boot_video_info *bvi = &bootsym(boot_vid_info);
 
+    /*
+     * fb detection will be in this order:
+     *  - efifb (as efifb probe sets a new GOP mode before parse_video_info is 
called,
+     *    we must use this mode instead of the one given by mbifb)
+     *  - mbifb
+     *  - vesafb
+     */
+
     /* vga_console_info is filled directly on EFI platform. */
     if ( efi_enabled(EFI_BOOT) )
         return;
 
-    if ( (bvi->orig_video_isVGA == 1) && (bvi->orig_video_mode == 3) )
+    if ( mbi->flags & MBI_FB )
+    {
+        uint64_t lfb_rgb_bitmap = 0;
+
+        vga_console_info.video_type = XEN_VGATYPE_VESA_LFB;
+        vga_console_info.u.vesa_lfb.width = mbi->fb.width;
+        vga_console_info.u.vesa_lfb.height = mbi->fb.height;
+        vga_console_info.u.vesa_lfb.bytes_per_line = mbi->fb.pitch;
+        vga_console_info.u.vesa_lfb.bits_per_pixel = mbi->fb.bpp;
+        vga_console_info.u.vesa_lfb.lfb_base = mbi->fb.addr;
+        vga_console_info.u.vesa_lfb.lfb_size = (mbi->fb.pitch * mbi->fb.height 
+ 0xffff) >> 16;
+
+        vga_console_info.u.vesa_lfb.red_pos = mbi->fb.red_pos;
+        vga_console_info.u.vesa_lfb.red_size = mbi->fb.red_size;
+        lfb_rgb_bitmap |= (((uint64_t)1 << mbi->fb.red_size) - 1) << 
mbi->fb.red_pos;
+        vga_console_info.u.vesa_lfb.green_pos = mbi->fb.green_pos;
+        vga_console_info.u.vesa_lfb.green_size = mbi->fb.green_size;
+        lfb_rgb_bitmap |= (((uint64_t)1 << mbi->fb.green_size) - 1) << 
mbi->fb.green_pos;
+        vga_console_info.u.vesa_lfb.blue_pos = mbi->fb.blue_pos;
+        vga_console_info.u.vesa_lfb.blue_size = mbi->fb.blue_size;
+        lfb_rgb_bitmap |= (((uint64_t)1 << mbi->fb.blue_size) - 1) << 
mbi->fb.blue_pos;
+
+        /* assume non-weird bit format */
+        vga_console_info.u.vesa_lfb.rsvd_pos = 
find_first_zero_bit(&lfb_rgb_bitmap, sizeof(lfb_rgb_bitmap) * __CHAR_BIT__);
+        vga_console_info.u.vesa_lfb.rsvd_size = mbi->fb.bpp - mbi->fb.red_size 
- mbi->fb.green_size - mbi->fb.blue_size;
+        if (vga_console_info.u.vesa_lfb.rsvd_pos >= mbi->fb.bpp || 
vga_console_info.u.vesa_lfb.rsvd_size < 0) {
+            vga_console_info.u.vesa_lfb.rsvd_pos = 0;
+            vga_console_info.u.vesa_lfb.rsvd_size = 0;
+        }
+        vga_console_info.u.vesa_lfb.gbl_caps = 2; /* possibly non-VGA */
+    }
+    else if ( (bvi->orig_video_isVGA == 1) && (bvi->orig_video_mode == 3) )
     {
         vga_console_info.video_type = XEN_VGATYPE_TEXT_MODE_3;
         vga_console_info.u.text_mode_3.font_height = bvi->orig_video_points;
@@ -933,7 +972,7 @@ void __init noreturn __start_xen(unsigned long mbi_p)
      */
     hypervisor_name = hypervisor_probe();
 
-    parse_video_info();
+    parse_video_info(mbi);
 
     rdmsrl(MSR_EFER, this_cpu(efer));
     asm volatile ( "mov %%cr4,%0" : "=r" (get_cpu_info()->cr4) );
-- 
2.25.1