From 97ffb299985abe8a713c519906e910359d4d2196 Mon Sep 17 00:00:00 2001 From: Ruihan Li Date: Mon, 15 Apr 2024 14:45:21 +0800 Subject: [PATCH] target/i386: Give IRQs a chance when resetting HF_INHIBIT_IRQ_MASK 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. This problem is caused because the previous code may choose not to end the TB even if the HF_INHIBIT_IRQ_MASK has just been reset (e.g., in the case where the STI instruction is immediately followed by the RET instruction), so that IRQs may not have a change to trigger. This commit fixes the problem by always terminating the current TB to give IRQs a chance to trigger when HF_INHIBIT_IRQ_MASK is reset. Reviewed-by: Richard Henderson Signed-off-by: Ruihan Li Message-ID: <20240415064518.4951-4-lrh2000@pku.edu.cn> Signed-off-by: Paolo Bonzini (cherry picked from commit 6a5a63f74ba5c5355b7a8468d3d814bfffe928fb) Signed-off-by: Michael Tokarev --- target/i386/tcg/translate.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/target/i386/tcg/translate.c b/target/i386/tcg/translate.c index 76a42c679c..c84196c00b 100644 --- a/target/i386/tcg/translate.c +++ b/target/i386/tcg/translate.c @@ -2798,13 +2798,17 @@ static void gen_bnd_jmp(DisasContext *s) static void do_gen_eob_worker(DisasContext *s, bool inhibit, bool recheck_tf, bool jr) { + bool inhibit_reset; + gen_update_cc_op(s); /* 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; + 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); } if (s->base.tb->flags & HF_RF_MASK) { @@ -2815,7 +2819,9 @@ do_gen_eob_worker(DisasContext *s, bool inhibit, bool recheck_tf, bool jr) tcg_gen_exit_tb(NULL, 0); } else if (s->flags & HF_TF_MASK) { gen_helper_single_step(tcg_env); - } else if (jr) { + } else if (jr && + /* give irqs a chance to happen */ + !inhibit_reset) { tcg_gen_lookup_and_goto_ptr(); } else { tcg_gen_exit_tb(NULL, 0);