From d079cc05873904c855bf2fb4d8db72fbb3727c9d Mon Sep 17 00:00:00 2001 From: =?utf8?q?Roger=20Pau=20Monn=C3=A9?= Date: Wed, 26 Feb 2020 17:38:58 +0100 Subject: [PATCH] x86/smp: do not use scratch_cpumask when in interrupt or exception context MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Using scratch_cpumask in send_IPI_mask is not safe in IRQ or exception context because it can nest, and hence send_IPI_mask could be overwriting another user scratch cpumask data when used in such contexts. Fallback to not using the scratch cpumask (and hence not attemping to optimize IPI sending by using a shorthand) when in IRQ or exception context. Note that the scratch cpumask cannot be used when non-maskable interrupts are being serviced (NMI or #MC) and hence fallback to not using the shorthand in that case, like it was done previously. Fixes: 5500d265a2a8 ('x86/smp: use APIC ALLBUT destination shorthand when possible') Reported-by: Sander Eikelenboom Signed-off-by: Roger Pau Monné Reviewed-by: Jan Beulich --- xen/arch/x86/smp.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/xen/arch/x86/smp.c b/xen/arch/x86/smp.c index fac295fa6f..a90c782d53 100644 --- a/xen/arch/x86/smp.c +++ b/xen/arch/x86/smp.c @@ -68,6 +68,18 @@ void send_IPI_mask(const cpumask_t *mask, int vector) bool cpus_locked = false; cpumask_t *scratch = this_cpu(scratch_cpumask); + if ( in_irq() || in_mce_handler() || in_nmi_handler() ) + { + /* + * When in IRQ, NMI or #MC context fallback to the old (and simpler) + * IPI sending routine, and avoid doing any performance optimizations + * (like using a shorthand) in order to avoid using the scratch + * cpumask which cannot be used in interrupt context. + */ + alternative_vcall(genapic.send_IPI_mask, mask, vector); + return; + } + /* * This can only be safely used when no CPU hotplug or unplug operations * are taking place, there are no offline CPUs (unless those have been -- 2.30.2