On 01/06/2015 09:47, Christian Borntraeger wrote: > > 1: "disable", "guest", "disable again and save", "restore to disable", "enable" > and now it is > 2: "disable", "guest", "enable" > and with your patch it is > 3: "disable", "guest", "enable", "disable, "enable" > > I assume that 3 and 1 are similar in its costs, so this is probably ok. At least on x86, 3 and 2 are similar, but 3 is much more expensive than 1! See https://lkml.org/lkml/2015/5/5/835: Cost of: CLI insn same-IF : 0 cycles Cost of: CLI insn flip-IF : 0 cycles Cost of: STI insn same-IF : 0 cycles Cost of: STI insn flip-IF : 0 cycles Cost of: PUSHF insn : 0 cycles Cost of: POPF insn same-IF : 20 cycles Cost of: POPF insn flip-IF : 28 cycles Cost of: local_irq_save() fn : 20 cycles Cost of: local_irq_restore() fn same-IF : 24 cycles Cost of: local_irq_restore() fn flip-IF : 28 cycles Cost of: irq_save()+restore() fn same-IF : 48 cycles Cost of: irq_save()+restore() fn flip-IF : 48 cycles Paolo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
