On Mon, Apr 15, 2024 at 8:50 AM Ruihan Li <lrh2...@pku.edu.cn> wrote:
>
> When emulated with QEMU, interrupts will never come in the following
> loop. However, if the NOP instruction is uncommented, interrupts will
> fire as normal.
>
> loop:
> cli
> call do_sti
> jmp loop
>
> do_sti:
> sti
> # nop
> ret
>
> This behavior is different from that of a real processor. For example,
> if KVM is enabled, interrupts will always fire regardless of whether the
> NOP instruction is commented or not. Also, the Intel Software Developer
> Manual states that after the STI instruction is executed, the interrupt
> inhibit should end as soon as the next instruction (e.g., the RET
> instruction if the NOP instruction is commented) is executed.
Thanks, interesting bug!
What do you think about writing this:
> /* If several instructions disable interrupts, only the first does it.
> */
> if (inhibit && !(s->flags & HF_INHIBIT_IRQ_MASK)) {
> gen_set_hflag(s, HF_INHIBIT_IRQ_MASK);
> - } else {
> + inhibit_reset = false;
> + } else if (!inhibit && (s->flags & HF_INHIBIT_IRQ_MASK)) {
> gen_reset_hflag(s, HF_INHIBIT_IRQ_MASK);
> + inhibit_reset = true;
> + } else {
> + inhibit_reset = false;
> }
in a slightly simpler manner:
inhibit_reset = false;
if (s->flags & HF_INHIBIT_IRQ_MASK) {
gen_reset_hflag(s, HF_INHIBIT_IRQ_MASK);
inhibit_reset = true;
} else if (inhibit) {
gen_set_hflag(s, HF_INHIBIT_IRQ_MASK);
}
No need to submit v3, I can do the change myself when applying.
Paolo
