From 348be43384e6bcd5e9da7ff5f1680d49f65c488d Mon Sep 17 00:00:00 2001 From: Juergen Gross Date: Fri, 29 Nov 2019 13:39:41 +0100 Subject: [PATCH] xen/events: remove event handling recursion detection __xen_evtchn_do_upcall() contains guards against being called recursively. This mechanism was introduced in the early pvops times (kernel 2.6.26) when there were all the Xen backend drivers missing from the upstream kernel, and some of those out-of-tree drivers were enabling interrupts in their event handlers (which was explicitly allowed in the initial XenoLinux). Nowadays we don't need to support those old drivers any more and the capability to allow recursive calls of __xen_evtchn_do_upcall() can be removed. Signed-off-by: Juergen Gross Reviewed-by: Boris Ostrovsky Signed-off-by: Juergen Gross --- drivers/xen/events/events_base.c | 16 +++------------- 1 file changed, 3 insertions(+), 13 deletions(-) diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c index 6c8843968a52..499eff7d3f65 100644 --- a/drivers/xen/events/events_base.c +++ b/drivers/xen/events/events_base.c @@ -1213,31 +1213,21 @@ void xen_send_IPI_one(unsigned int cpu, enum ipi_vector vector) notify_remote_via_irq(irq); } -static DEFINE_PER_CPU(unsigned, xed_nesting_count); - static void __xen_evtchn_do_upcall(void) { struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu); - int cpu = get_cpu(); - unsigned count; + int cpu = smp_processor_id(); do { vcpu_info->evtchn_upcall_pending = 0; - if (__this_cpu_inc_return(xed_nesting_count) - 1) - goto out; - xen_evtchn_handle_events(cpu); BUG_ON(!irqs_disabled()); - count = __this_cpu_read(xed_nesting_count); - __this_cpu_write(xed_nesting_count, 0); - } while (count != 1 || vcpu_info->evtchn_upcall_pending); + virt_rmb(); /* Hypervisor can set upcall pending. */ -out: - - put_cpu(); + } while (vcpu_info->evtchn_upcall_pending); } void xen_evtchn_do_upcall(struct pt_regs *regs)