C Kernel - Runs fine in Qemu but not in VM - c

Question

I am developing a kernel from scratch in C. I am having a problem with the keyboard. In Qemu, when I press a key on my keyboard, the keypress is handled normally. When I run it in VirtualBox or on an actual computer, it works fine until I press a key. In virtualbox, when it crashes, it gives me the error code VINF_EM_TRIPLE_FAULT. Here is my (important parts) of the code:
Assembly:
bits 32
section .text
;multiboot spec
align 4
dd 0x1BADB002 ;magic
dd 0x00 ;flags
dd - (0x1BADB002 + 0x00)
global start
global keyboard_handler
global read_port
global write_port
global load_idt
extern main ;this is defined in the c file
extern keyboard_handler_main
read_port:
mov edx, [esp + 4]
;al is the lower 8 bits of eax
in al, dx ;dx is the lower 16 bits of edx
ret
write_port:
mov edx, [esp + 4]
mov al, [esp + 4 + 4]
out dx, al
ret
load_idt:
mov edx, [esp + 4]
lidt [edx]
sti ;turn on interrupts
ret
keyboard_handler:
call keyboard_handler_main
iretd
start:
cli ;block interrupts
mov esp, stack_space
call main
hlt ;halt the CPU
section .bss
resb 8192; 8KB for stack
stack_space:
C (The important parts, I omitted parts that don't involve the keyboard):
struct IDT_entry{
unsigned short int offset_lowerbits;
unsigned short int selector;
unsigned char zero;
unsigned char type_attr;
unsigned short int offset_higherbits;
};
struct IDT_entry IDT[IDT_SIZE];
void idt_init(void)
{
unsigned long keyboard_address;
unsigned long idt_address;
unsigned long idt_ptr[2];
/* populate IDT entry of keyboard's interrupt */
keyboard_address = (unsigned long)keyboard_handler;
IDT[0x21].offset_lowerbits = keyboard_address & 0xffff;
IDT[0x21].selector = KERNEL_CODE_SEGMENT_OFFSET;
IDT[0x21].zero = 0;
IDT[0x21].type_attr = INTERRUPT_GATE;
IDT[0x21].offset_higherbits = (keyboard_address & 0xffff0000) >> 16;
/* Ports
* PIC1 PIC2
*Command 0x20 0xA0
*Data 0x21 0xA1
*/
/* ICW1 - begin initialization */
write_port(0x20 , 0x11);
write_port(0xA0 , 0x11);
/* ICW2 - remap offset address of IDT */
/*
* In x86 protected mode, we have to remap the PICs beyond 0x20 because
* Intel have designated the first 32 interrupts as "reserved" for cpu exceptions
*/
write_port(0x21 , 0x20);
write_port(0xA1 , 0x28);
/* ICW3 - setup cascading */
write_port(0x21 , 0x00);
write_port(0xA1 , 0x00);
/* ICW4 - environment info */
write_port(0x21 , 0x01);
write_port(0xA1 , 0x01);
/* Initialization finished */
/* mask interrupts */
write_port(0x21 , 0xff);
write_port(0xA1 , 0xff);
/* fill the IDT descriptor */
idt_address = (unsigned long)IDT ;
idt_ptr[0] = (sizeof (struct IDT_entry) * IDT_SIZE) + ((idt_address & 0xffff) << 16);
idt_ptr[1] = idt_address >> 16 ;
load_idt(idt_ptr);
}
void kb_init(void)
{
/* 0xFD is 11111101 - enables only IRQ1 (keyboard)*/
write_port(0x21 , 0xFD);
}
void keyboard_handler_main(void) {
unsigned char status;
char keycode;
/* write EOI */
write_port(0x20, 0x20);
status = read_port(KEYBOARD_STATUS_PORT);
/* Lowest bit of status will be set if buffer is not empty */
if (status & 0x01) {
keycode = read_port(KEYBOARD_DATA_PORT);
if(keycode < 0){
return;
}
char c = keyboard_map[(unsigned char) keycode]; //keyboard_map converts key codes to ASCII
(prints the char)
}
}
}
void main(void)
{
idt_init();
kb_init();
while(1);
print("Welcome to Code OS");
}
And then of course they are compiled with a linker.
So why is this working in qemu but not an actual computer? (On an actual computer it works fine until I press any key.)