On Fri, Dec 05, 2025 at 10:23:42AM -0800, Sean Christopherson wrote:
> 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?
>
Yes, this also breaks the testcase regarding KVM_GUESTDBG_BLOCKIRQ.
Sorry, I forgot why I added this, as you said there should be no IRQ
delivered due to the STI shadow. :(
I'll remove it in the next version.
Thanks!
> > +
> > /* Test software BPs - int3 */
> > memset(&debug, 0, sizeof(debug));
> > debug.control = KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_SW_BP;
> > --
> > 2.31.1
> >
