On Wed, Sep 10, 2025, Hou Wenlong wrote:
> #define IRQ_VECTOR 0xAA
>
> +#define CAST_TO_RIP(v) ((unsigned long long)&(v))
> +
> /* For testing data access debug BP */
> uint32_t guest_value;
>
> extern unsigned char sw_bp, hw_bp, write_data, ss_start, bd_start;
> -extern unsigned char fep_bd_start;
> +extern unsigned char fep_bd_start, fep_sti_start, fep_sti_end;
> +
> +static void guest_db_handler(struct ex_regs *regs)
> +{
> + static int count;
> + unsigned long target_rips[2] = {
> + CAST_TO_RIP(fep_sti_start),
> + CAST_TO_RIP(fep_sti_end),
> + };
> +
> + __GUEST_ASSERT(regs->rip == target_rips[count], "STI: unexpected rip
> 0x%lx (should be 0x%lx)",
> + regs->rip, target_rips[count]);
> + regs->rflags &= ~X86_EFLAGS_TF;
> + count++;
> +}
> +
> +static void guest_irq_handler(struct ex_regs *regs)
> +{
> +}
>
> static void guest_code(void)
> {
> @@ -69,13 +89,25 @@ static void guest_code(void)
> if (is_forced_emulation_enabled) {
> /* DR6.BD test for emulation */
> asm volatile(KVM_FEP "fep_bd_start: mov %%dr0, %%rax" : : :
> "rax");
> +
> + /* pending debug exceptions for emulation */
> + asm volatile("pushf\n\t"
> + "orq $" __stringify(X86_EFLAGS_TF) ", (%rsp)\n\t"
> + "popf\n\t"
> + "sti\n\t"
> + "fep_sti_start:"
> + "cli\n\t"
> + "pushf\n\t"
> + "orq $" __stringify(X86_EFLAGS_TF) ", (%rsp)\n\t"
> + "popf\n\t"
> + KVM_FEP "sti\n\t"
> + "fep_sti_end:"
> + "cli\n\t");
> }
>
> GUEST_DONE();
> }
>
> -#define CAST_TO_RIP(v) ((unsigned long long)&(v))
> -
> static void vcpu_skip_insn(struct kvm_vcpu *vcpu, int insn_len)
> {
> struct kvm_regs regs;
> @@ -110,6 +142,9 @@ int main(void)
> vm = vm_create_with_one_vcpu(&vcpu, guest_code);
> run = vcpu->run;
>
> + vm_install_exception_handler(vm, DB_VECTOR, guest_db_handler);
> + vm_install_exception_handler(vm, IRQ_VECTOR, guest_irq_handler);
But the IRQ should never be taken thanks to the CLI in the STI shadow. I.e.
installing a dummy handler could mask failures, no?
> +
> /* Test software BPs - int3 */
> memset(&debug, 0, sizeof(debug));
> debug.control = KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_SW_BP;
> --
> 2.31.1
>
