x86, setup: Don't skip mode setting for the standard VGA modes

The code for setting standard VGA modes probes for the current mode,
and skips the mode setting if the mode is 3 (color text 80x25) or 7
(mono text 80x25).  Unfortunately, there are BIOSes, including the
VMware BIOS, which report the previous mode if function 0F is queried
while the screen is in a VESA mode, and of course, nothing can help a
mode poked directly into the hardware.

As such, the safe option is to set the mode anyway, and only query to
see if we should be using mode 7 rather than mode 3.  People who don't
want any mode setting at all should probably use vga=0x0f04
(VIDEO_CURRENT_MODE).  It's possible that should be the kernel
default.

Reported-by Rene Arends <R.R.Arends@hro.nl>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
LKML-Reference: <tip-*@git.kernel.org>

1 files changed, 1 insertions, 8 deletions

diff --git a/arch/x86/boot/video-vga.c b/arch/x86/boot/video-vga.c
index 819caa1f2008..ed7aeff786b2 100644
--- a/arch/x86/boot/video-vga.c
+++ b/arch/x86/boot/video-vga.c
@@ -42,22 +42,15 @@ static u8 vga_set_basic_mode(void)
 {
 	struct biosregs ireg, oreg;
 	u16 ax;
-	u8 rows;
 	u8 mode;
 
 	initregs(&ireg);
 
+	/* Query current mode */
 	ax = 0x0f00;
 	intcall(0x10, &ireg, &oreg);
 	mode = oreg.al;
 
-	set_fs(0);
-	rows = rdfs8(0x484);	/* rows minus one */
-
-	if ((oreg.ax == 0x5003 || oreg.ax == 0x5007) &&
-	    (rows == 0 || rows == 24))
-		return mode;
-
 	if (mode != 3 && mode != 7)
 		mode = 3;