From: "Luis R. Rodriguez" <mcgrof@xxxxxxxx> After my last respin Andy provided some ideas as how to skip IRQ context hacks for preemption, this v3 spin addresses that and a bit more. This is based on both Andrew Cooper's and David Vrabel's work, further modified based on ideas by Andy Lutomirski to avoid having to deal with preemption on IRQ context. Ian had originally suggested to avoid the pt_regs stuff by using a CPU variable but based on Andy's observations it is difficult to prove we will avoid recursing or bad nesting when dealing with preemption out of IRQ context. This is specially true given that after a hypercall gets preempted the hypercall may end up another CPU. This uses NOKPROBE_SYMBOL and notrace since based on Andy's advice I am not confident that tracing and kprobes are safe to use in what might be an extended RCU quiescent state (i.e. where we're outside irq_enter and irq_exit). I've tested this on 64-bit, some testing on 32-bit would be appreciated. Luis R. Rodriguez (2): x86/xen: add xen_is_preemptible_hypercall() x86/xen: allow privcmd hypercalls to be preempted arch/x86/include/asm/xen/hypercall.h | 20 ++++++++++++++++++++ arch/x86/kernel/entry_32.S | 2 ++ arch/x86/kernel/entry_64.S | 2 ++ arch/x86/xen/enlighten.c | 7 +++++++ arch/x86/xen/xen-head.S | 18 +++++++++++++++++- drivers/xen/events/events_base.c | 13 +++++++++++++ include/xen/events.h | 1 + 7 files changed, 62 insertions(+), 1 deletion(-) -- 2.1.1 -- 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
