Fix attached for qemu. It would be nice to know if this causes trouble for real hardware, but it should not.
ron
There are some problems with the way these interrrupts were managed. First, the CLI erases any knowledge of whether interrupts were enabled or disabled. Second, the STI works badly on qemu; we get an immediate INT #0 as soon as the STI happens. This doesn't happen on real hardware but, that said, I don't think this code should be doing cli and sti. This change fixes the observed qemu failures. Signed-off-by: Ronald G. Minnich <[email protected]> Index: /home/rminnich/src/bios/coreboot-v2/util/x86emu/x86_asm.S =================================================================== --- /home/rminnich/src/bios/coreboot-v2/util/x86emu/x86_asm.S (revision 1171) +++ /home/rminnich/src/bios/coreboot-v2/util/x86emu/x86_asm.S (working copy) @@ -71,11 +71,6 @@ // FIXME: Should this function be called with regparm=0? movl 8(%ebp), %ecx - /* Clear interrupts before making a - * transition to Real Mode - */ - cli - /* Activate the right segment descriptor real mode. */ ljmp $0x28, $RELOCATED(1f) 1: @@ -111,14 +106,11 @@ movl $0x1000, %eax movl %eax, %esp - /* Load our 16 it idt */ + /* Load our 16 bit idt */ xor %ax, %ax mov %ax, %ds lidt __realmode_idt - /* All critical work is done, allow interrupts again */ - sti - /* Set all segments to 0x0000, ds to 0x0040 */ mov %ax, %es mov %ax, %fs @@ -133,11 +125,6 @@ lcall $0xc000, $0x0003 /* ************************************ */ - /* Clear interrupts before making a - * transition to Protected Mode - */ - cli - /* If we got here, just about done. * Need to get back to protected mode */ @@ -161,9 +148,6 @@ /* restore proper idt */ lidt idtarg - /* All critical work is done, allow interrupts again */ - sti - /* and exit */ mov __stack, %esp popal @@ -179,11 +163,6 @@ mov %esp, __stack - /* Clear interrupts before making a - * transition to Real Mode - */ - cli - /* This configures CS properly for real mode. */ ljmp $0x28, $RELOCATED(1f) 1: @@ -228,9 +207,6 @@ mov %ax, %ds lidt __realmode_idt - /* All critical work is done, allow interrupts again */ - sti - /* Set all segments to 0x0000 */ mov %ax, %ds mov %ax, %es @@ -250,11 +226,6 @@ movw $0, %di int $0x10 - /* Clear interrupts before making a - * transition to Protected Mode - */ - cli - /* Ok, the job is done, now go back to protected mode coreboot */ movl %cr0, %eax orl $PE, %eax @@ -274,9 +245,6 @@ /* restore coreboot's 32-bit IDT */ lidt idtarg - /* All critical work is done, allow interrupts again */ - sti - /* Exit */ mov __stack, %esp popal @@ -299,11 +267,6 @@ andl $0xff, %eax pushl %eax /* ... and make it the first parameter */ - /* Clear interrupts before making a - * transition to Protected Mode - */ - cli - /* Switch to protected mode */ movl %cr0, %eax orl $PE, %eax @@ -322,9 +285,6 @@ lidt idtarg - /* All critical work is done, allow interrupts again */ - sti - /* Call the C interrupt handler */ movl $interrupt_handler, %eax call *%eax @@ -344,11 +304,6 @@ mov %ax, %gs mov %ax, %ss - /* Clear interrupts before making a - * transition to Real Mode - */ - cli - /* Disable Protected Mode */ movl %cr0, %eax andl $~PE, %eax @@ -366,9 +321,6 @@ mov %ax, %ds lidt __realmode_idt - /* All critical work is done, allow interrupts again */ - sti - /* Set up our segment registers to segment 0x0000 */ mov %ax, %es mov %ax, %fs
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