[2/3] vga: Add endian control register

From: Benjamin Herrenschmidt <benh@kernel.crashing.org>

Include the endian state in the migration stream as an optional
subsection which we only include when the endian isn't the default,
thus enabling backward compatibility of the common case.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

Changes by kraxel:
 * Remove bochs dispi interface changes.  We'll do that in
   a different way to make sure we don't conflict with
   possible future bochs dispi interface changes.
 * keep live migration bits.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 hw/display/vga.c     | 41 +++++++++++++++++++++++++++++++++++++----
 hw/display/vga_int.h |  4 +++-
 2 files changed, 40 insertions(+), 5 deletions(-)

On Tue, Sep 23, 2014 at 02:30:56PM +0200, Gerd Hoffmann wrote:
> From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> 
> Include the endian state in the migration stream as an optional
> subsection which we only include when the endian isn't the default,
> thus enabling backward compatibility of the common case.
> 
> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> 
> Changes by kraxel:
>  * Remove bochs dispi interface changes.  We'll do that in
>    a different way to make sure we don't conflict with
>    possible future bochs dispi interface changes.
>  * keep live migration bits.
> 
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
>  hw/display/vga.c     | 41 +++++++++++++++++++++++++++++++++++++----
>  hw/display/vga_int.h |  4 +++-
>  2 files changed, 40 insertions(+), 5 deletions(-)
> 
> diff --git a/hw/display/vga.c b/hw/display/vga.c
> index 3f02984..fd16806 100644
> --- a/hw/display/vga.c
> +++ b/hw/display/vga.c
> @@ -1508,7 +1508,8 @@ static void vga_draw_graphic(VGACommonState *s, int full_update)
>      if (s->line_offset != s->last_line_offset ||
>          disp_width != s->last_width ||
>          height != s->last_height ||
> -        s->last_depth != depth) {
> +        s->last_depth != depth ||
> +        s->last_byteswap != byteswap) {
>          if (depth == 32 || (depth == 16 && !byteswap)) {
>              pixman_format_code_t format =
>                  qemu_default_pixman_format(depth, !byteswap);
> @@ -1526,6 +1527,7 @@ static void vga_draw_graphic(VGACommonState *s, int full_update)
>          s->last_height = height;
>          s->last_line_offset = s->line_offset;
>          s->last_depth = depth;
> +        s->last_byteswap = byteswap;
>          full_update = 1;
>      } else if (is_buffer_shared(surface) &&
>                 (full_update || surface_data(surface) != s->vram_ptr
> @@ -1789,6 +1791,7 @@ void vga_common_reset(VGACommonState *s)
>      s->cursor_start = 0;
>      s->cursor_end = 0;
>      s->cursor_offset = 0;
> +    s->big_endian_fb = s->default_endian_fb;
>      memset(s->invalidated_y_table, '\0', sizeof(s->invalidated_y_table));
>      memset(s->last_palette, '\0', sizeof(s->last_palette));
>      memset(s->last_ch_attr, '\0', sizeof(s->last_ch_attr));
> @@ -2020,6 +2023,28 @@ static int vga_common_post_load(void *opaque, int version_id)
>      return 0;
>  }
>  
> +static bool vga_endian_state_needed(void *opaque)
> +{
> +    VGACommonState *s = opaque;
> +
> +    /*
> +     * Only send the endian state if it's different from the
> +     * default one, thus ensuring backward compatibility for
> +     * migration of the common case
> +     */
> +    return s->default_endian_fb != s->big_endian_fb;
> +}
> +
> +const VMStateDescription vmstate_vga_endian = {
> +    .name = "vga.endian",
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_UINT8_EQUAL(big_endian_fb, VGACommonState),

I don't think this is right.  If I'm remembering how the vmstate
macros work, this will abort if big_endian_fb isn't equal on source
and destination.  Which means as soon as it's possible to actually
change the big_endian_fb value, migrations will start failing/

I think this should instead be VMSTATE_BOOL()

[snip]
> -    bool big_endian_fb;
> +    uint8_t big_endian_fb;
> +    uint8_t default_endian_fb;
>      /* hardware mouse cursor support */
>      uint32_t invalidated_y_table[VGA_MAX_HEIGHT / 32];
>      void (*cursor_invalidate)(struct VGACommonState *s);

In which case you also don't need to change the type of the
big_endian_fb field.