diff options
| author | Juergen Gross <jgross@suse.com> | 2023-10-24 13:51:36 +0200 |
|---|---|---|
| committer | Juergen Gross <jgross@suse.com> | 2023-11-13 07:22:00 +0100 |
| commit | e64e7c74b99ec9e439abca75f522f4b98f220bd1 (patch) | |
| tree | bf1beaabc09842d03aa36ae4307e3ec00d7620d6 | |
| parent | b85ea95d086471afb4ad062012a4d73cd328fa86 (diff) | |
xen/events: avoid using info_for_irq() in xen_send_IPI_one()
xen_send_IPI_one() is being used by cpuhp_report_idle_dead() after
it calls rcu_report_dead(), meaning that any RCU usage by
xen_send_IPI_one() is a bad idea.
Unfortunately xen_send_IPI_one() is using notify_remote_via_irq()
today, which is using irq_get_chip_data() via info_for_irq(). And
irq_get_chip_data() in turn is using a maple-tree lookup requiring
RCU.
Avoid this problem by caching the ipi event channels in another
percpu variable, allowing the use notify_remote_via_evtchn() in
xen_send_IPI_one().
Fixes: 721255b9826b ("genirq: Use a maple tree for interrupt descriptor management")
Reported-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Juergen Gross <jgross@suse.com>
Tested-by: David Woodhouse <dwmw@amazon.co.uk>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>
Signed-off-by: Juergen Gross <jgross@suse.com>
| -rw-r--r-- | drivers/xen/events/events_base.c | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c index 6de6b084ea60..237e6b884f72 100644 --- a/drivers/xen/events/events_base.c +++ b/drivers/xen/events/events_base.c @@ -164,6 +164,8 @@ static DEFINE_PER_CPU(int [NR_VIRQS], virq_to_irq) = {[0 ... NR_VIRQS-1] = -1}; /* IRQ <-> IPI mapping */ static DEFINE_PER_CPU(int [XEN_NR_IPIS], ipi_to_irq) = {[0 ... XEN_NR_IPIS-1] = -1}; +/* Cache for IPI event channels - needed for hot cpu unplug (avoid RCU usage). */ +static DEFINE_PER_CPU(evtchn_port_t [XEN_NR_IPIS], ipi_to_evtchn) = {[0 ... XEN_NR_IPIS-1] = 0}; /* Event channel distribution data */ static atomic_t channels_on_cpu[NR_CPUS]; @@ -366,6 +368,7 @@ static int xen_irq_info_ipi_setup(unsigned cpu, info->u.ipi = ipi; per_cpu(ipi_to_irq, cpu)[ipi] = irq; + per_cpu(ipi_to_evtchn, cpu)[ipi] = evtchn; return xen_irq_info_common_setup(info, irq, IRQT_IPI, evtchn, 0); } @@ -981,6 +984,7 @@ static void __unbind_from_irq(unsigned int irq) break; case IRQT_IPI: per_cpu(ipi_to_irq, cpu)[ipi_from_irq(irq)] = -1; + per_cpu(ipi_to_evtchn, cpu)[ipi_from_irq(irq)] = 0; break; case IRQT_EVTCHN: dev = info->u.interdomain; @@ -1632,7 +1636,7 @@ EXPORT_SYMBOL_GPL(evtchn_put); void xen_send_IPI_one(unsigned int cpu, enum ipi_vector vector) { - int irq; + evtchn_port_t evtchn; #ifdef CONFIG_X86 if (unlikely(vector == XEN_NMI_VECTOR)) { @@ -1643,9 +1647,9 @@ void xen_send_IPI_one(unsigned int cpu, enum ipi_vector vector) return; } #endif - irq = per_cpu(ipi_to_irq, cpu)[vector]; - BUG_ON(irq < 0); - notify_remote_via_irq(irq); + evtchn = per_cpu(ipi_to_evtchn, cpu)[vector]; + BUG_ON(evtchn == 0); + notify_remote_via_evtchn(evtchn); } struct evtchn_loop_ctrl { |