From: Paolo Bonzini Date: Sat, 25 May 2024 09:16:14 +0000 (+0200) Subject: target/i386: document use of DISAS_NORETURN X-Git-Tag: qemu-xen-4.20.0~119^2~31 X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=b37c0dc85214e9d5e4a9b6f6a496ce4de3b8a4d6;p=qemu-xen.git target/i386: document use of DISAS_NORETURN DISAS_NORETURN suppresses the work normally done by gen_eob(), and therefore must be used in special cases only. Document them. Signed-off-by: Paolo Bonzini --- diff --git a/target/i386/tcg/translate.c b/target/i386/tcg/translate.c index a9c6424c7d..2b6f67be40 100644 --- a/target/i386/tcg/translate.c +++ b/target/i386/tcg/translate.c @@ -4761,6 +4761,17 @@ static void i386_tr_tb_stop(DisasContextBase *dcbase, CPUState *cpu) switch (dc->base.is_jmp) { case DISAS_NORETURN: + /* + * Most instructions should not use DISAS_NORETURN, as that suppresses + * the handling of hflags normally done by gen_eob(). We can + * get here: + * - for exception and interrupts + * - for jump optimization (which is disabled by INHIBIT_IRQ/RF/TF) + * - for VMRUN because RF/TF handling for the host is done after vmexit, + * and INHIBIT_IRQ is loaded from the VMCB + * - for HLT/PAUSE/MWAIT to exit the main loop with specific EXCP_* values; + * the helpers handle themselves the tasks normally done by gen_eob(). + */ break; case DISAS_TOO_MANY: gen_update_cc_op(dc);