[Minios-devel] [UNIKRAFT PATCH v2 1/1] plat/kvm: Update VGA console cursor location

[Florian Schmidt <florian.schmidt@xxxxxxxxx>]

Update the location of the cursor as data is written to the console.
Note that this does not set the cursor location registers, hence all we
get is the blinking underline character, not the full-size block
character.

Signed-off-by: Florian Schmidt <florian.schmidt@xxxxxxxxx>
---
 plat/kvm/x86/vga_console.c | 47 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/plat/kvm/x86/vga_console.c b/plat/kvm/x86/vga_console.c
index ff825e3..f565b1c 100644
--- a/plat/kvm/x86/vga_console.c
+++ b/plat/kvm/x86/vga_console.c
@@ -29,6 +29,8 @@
 #include <sys/types.h>
 #include <stdint.h>
 #include <string.h>
+#include <x86/cpu.h>
+#include <x86/irq.h>
 #include <kvm-x86/vga_console.h>
 
 /* Hardware text mode color constants. */
@@ -69,6 +71,8 @@ static size_t terminal_row;
 static size_t terminal_column;
 static uint8_t terminal_color;
 static uint16_t *terminal_buffer;
+static uint16_t areg;   /* VGA address register */
+static uint16_t dreg;   /* VGA data register */
 
 static void clear_terminal(void)
 {
@@ -83,9 +87,36 @@ static void clear_terminal(void)
 
 void _libkvmplat_init_vga_console(void)
 {
+       unsigned long irq_flags;
+
        terminal_row = 0;
        terminal_column = 0;
        terminal_color = vga_entry_color(VGA_COLOR_LIGHT_GREY, VGA_COLOR_BLACK);
+
+       local_irq_save(irq_flags);
+       /* Location of the address and data registers is variable and denoted
+        * by the least significant bit in the Input/Output register located
+        * at 0x3cc. For our emulated color display, they should always be
+        * 0x3d{4,5}, but better safe than sorry, so let's check at init time.
+        */
+       if (inb(0x3cc) & 0x1) {
+               areg = 0x3d4;
+               dreg = 0x3d5;
+       } else {
+               areg = 0x3b4;
+               dreg = 0x3b5;
+       }
+
+       /* Initialize cursor appearance. Setting CURSOR_START (0x0a) to 0x0e
+        * and CURSOR_END (0x0b) to 0x0f enables the cursor and produces
+        * a blinking underscore.
+        */
+       outb(areg, 0x0a);
+       outb(dreg, 0x0e);
+       outb(areg, 0x0b);
+       outb(dreg, 0x0f);
+       local_irq_restore(irq_flags);
+
        terminal_buffer = (uint16_t *) 0xb8000;
        clear_terminal();
 }
@@ -109,6 +140,21 @@ static void vga_scroll(void)
                        = vga_entry(' ', terminal_color);
 }
 
+static void vga_update_cursor(void)
+{
+       unsigned long irq_flags;
+       uint8_t old;
+
+       local_irq_save(irq_flags);
+       old = inb(areg);
+       outb(areg, 0x0e); // Cursor Location High
+       outb(dreg, ((terminal_row * VGA_WIDTH) + terminal_column) >> 8);
+       outb(areg, 0x0f); // Cursor Location Low
+       outb(dreg, ((terminal_row * VGA_WIDTH) + terminal_column) & 0xff);
+       outb(areg, old);
+       local_irq_restore(irq_flags);
+}
+
 static void vga_newline(void)
 {
        if (terminal_row == VGA_HEIGHT - 1)
@@ -157,4 +203,5 @@ void _libkvmplat_vga_putc(char c)
                }
                break;
        }
+       vga_update_cursor();
 }
-- 
2.18.0


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