[SeaBIOS] [PATCH v2 6/6] cbvga_set_mode: disable clearmem in windows x86 emulator.

[Gerd Hoffmann]

On Wed, Jun 20, 2018 at 08:00:28PM +0200, Patrick Rudolph wrote:
> On Mon, 2018-06-04 at 09:31 -0400, Kevin O'Connor wrote:
> > On Mon, Jun 04, 2018 at 09:29:17AM +0200, Gerd Hoffmann wrote:
> > > Signed-off-by: Gerd Hoffmann <kraxel at redhat.com>
> > > ---
> > >  vgasrc/cbvga.c | 10 +++++++++-
> > >  1 file changed, 9 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/vgasrc/cbvga.c b/vgasrc/cbvga.c
> > > index 3f16bee10c..f6ebe71242 100644
> > > --- a/vgasrc/cbvga.c
> > > +++ b/vgasrc/cbvga.c
> > > @@ -192,8 +192,16 @@ int
> > >  cbvga_set_mode(struct vgamode_s *vmode_g, int flags)
> > >  {
> > >      u8 emul = vmode_g == &CBemulinfo || GET_GLOBAL(CBmode) == 0x03;
> > > +    /*
> > > +     * The extra_stack flag is false when running in windows x86
> > > +     * emulator, to avoid stack switching triggering bugs.  Using the
> > > +     * same flag here to skip screen clearing, because the windows
> > > +     * emulator seems to have problems to handle the int 1587 call
> > > +     * too, and GO_MEMSET uses that.
> > > +     */
> > > +    u8 extra_stack = GET_BDA_EXT(flags) & BF_EXTRA_STACK;
> > >      MASK_BDA_EXT(flags, BF_EMULATE_TEXT, emul ? BF_EMULATE_TEXT : 0);
> > > -    if (!(flags & MF_NOCLEARMEM)) {
> > > +    if (!(flags & MF_NOCLEARMEM) && extra_stack) {
> > 
> > FYI, extra_stack will only be true if CONFIG_VGA_ALLOCATE_EXTRA_STACK
> > is set, but I guess that's okay.
> > 
> > Thanks, the series looks good to me.
> > -Kevin
> This commit breaks SeaBIOS' menu when used with coreboot's native
> graphic init in text mode. Payloads are not affacted (tested NTLDR and
> coreinfo).
> Everything works fine with native graphic init in high resolution
> framebuffer mode. I've got no debug log at hand, but I'll investigate
> asap.
> Tested on Lenovo T500 using libgfxinit with latest coreboot master.

Hmm, no clue what could cause this.  But clearing the memory is only
problematic for the framebuffer case, so maybe the patch below helps?

diff --git a/vgasrc/cbvga.c b/vgasrc/cbvga.c
index f6ebe71242..a48f4dc885 100644
--- a/vgasrc/cbvga.c
+++ b/vgasrc/cbvga.c
@@ -201,18 +201,20 @@ cbvga_set_mode(struct vgamode_s *vmode_g, int flags)
      */
     u8 extra_stack = GET_BDA_EXT(flags) & BF_EXTRA_STACK;
     MASK_BDA_EXT(flags, BF_EMULATE_TEXT, emul ? BF_EMULATE_TEXT : 0);
-    if (!(flags & MF_NOCLEARMEM) && extra_stack) {
+    if (!(flags & MF_NOCLEARMEM)) {
         if (GET_GLOBAL(CBmodeinfo.memmodel) == MM_TEXT) {
             memset16_far(SEG_CTEXT, (void*)0, 0x0720, 80*25*2);
             return 0;
         }
-        struct gfx_op op;
-        init_gfx_op(&op, &CBmodeinfo);
-        op.x = op.y = 0;
-        op.xlen = GET_GLOBAL(CBmodeinfo.width);
-        op.ylen = GET_GLOBAL(CBmodeinfo.height);
-        op.op = GO_MEMSET;
-        handle_gfx_op(&op);
+        if (extra_stack) {
+            struct gfx_op op;
+            init_gfx_op(&op, &CBmodeinfo);
+            op.x = op.y = 0;
+            op.xlen = GET_GLOBAL(CBmodeinfo.width);
+            op.ylen = GET_GLOBAL(CBmodeinfo.height);
+            op.op = GO_MEMSET;
+            handle_gfx_op(&op);
+        }
     }
     return 0;
 }