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authorNeil Horman <nhorman@tuxdriver.com>2019-08-22 10:34:21 -0400
committerThomas Gleixner <tglx@linutronix.de>2019-08-28 14:44:08 +0200
commit743dac494d61d991967ebcfab92e4f80dc7583b3 (patch)
tree006fe0ccdc04cc976cda0ad3d3cce339bf76b8ba /arch/x86/kernel/apic
parent6444b40eeda4f78f57b255dd7ecb8d3e5936eea2 (diff)
x86/apic/vector: Warn when vector space exhaustion breaks affinity
On x86, CPUs are limited in the number of interrupts they can have affined to them as they only support 256 interrupt vectors per CPU. 32 vectors are reserved for the CPU and the kernel reserves another 22 for internal purposes. That leaves 202 vectors for assignement to devices. When an interrupt is set up or the affinity is changed by the kernel or the administrator, the vector assignment code attempts to honor the requested affinity mask. If the vector space on the CPUs in that affinity mask is exhausted the code falls back to a wider set of CPUs and assigns a vector on a CPU outside of the requested affinity mask silently. While the effective affinity is reflected in the corresponding /proc/irq/$N/effective_affinity* files the silent breakage of the requested affinity can lead to unexpected behaviour for administrators. Add a pr_warn() when this happens so that adminstrators get at least informed about it in the syslog. [ tglx: Massaged changelog and made the pr_warn() more informative ] Reported-by: djuran@redhat.com Signed-off-by: Neil Horman <nhorman@tuxdriver.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: djuran@redhat.com Link: https://lkml.kernel.org/r/20190822143421.9535-1-nhorman@tuxdriver.com
Diffstat (limited to 'arch/x86/kernel/apic')
-rw-r--r--arch/x86/kernel/apic/vector.c11
1 files changed, 11 insertions, 0 deletions
diff --git a/arch/x86/kernel/apic/vector.c b/arch/x86/kernel/apic/vector.c
index fdacb864c3dd..2c5676b0a6e7 100644
--- a/arch/x86/kernel/apic/vector.c
+++ b/arch/x86/kernel/apic/vector.c
@@ -398,6 +398,17 @@ static int activate_reserved(struct irq_data *irqd)
if (!irqd_can_reserve(irqd))
apicd->can_reserve = false;
}
+
+ /*
+ * Check to ensure that the effective affinity mask is a subset
+ * the user supplied affinity mask, and warn the user if it is not
+ */
+ if (!cpumask_subset(irq_data_get_effective_affinity_mask(irqd),
+ irq_data_get_affinity_mask(irqd))) {
+ pr_warn("irq %u: Affinity broken due to vector space exhaustion.\n",
+ irqd->irq);
+ }
+
return ret;
}