The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 005c34ae4b44f085120d7f371121ec7ded677761 Mon Sep 17 00:00:00 2001

From: Marc Zyngier maz@kernel.org Date: Sun, 21 Jun 2020 14:43:15 +0100 Subject: [PATCH] irqchip/gic: Atomically update affinity

The GIC driver uses a RMW sequence to update the affinity, and relies on the gic_lock_irqsave/gic_unlock_irqrestore sequences to update it atomically.

But these sequences only expand into anything meaningful if the BL_SWITCHER option is selected, which almost never happens.

It also turns out that using a RMW and locks is just as silly, as the GIC distributor supports byte accesses for the GICD_TARGETRn registers, which when used make the update atomic by definition.

Drop the terminally broken code and replace it by a byte write.

Fixes: 04c8b0f82c7d ("irqchip/gic: Make locking a BL_SWITCHER only feature") Cc: stable@vger.kernel.org Signed-off-by: Marc Zyngier maz@kernel.org

diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c index 00de05abd3c3..c17fabd6741e 100644 --- a/drivers/irqchip/irq-gic.c +++ b/drivers/irqchip/irq-gic.c @@ -329,10 +329,8 @@ static int gic_irq_set_vcpu_affinity(struct irq_data *d, void *vcpu) static int gic_set_affinity(struct irq_data *d, const struct cpumask *mask_val, bool force) { - void __iomem *reg = gic_dist_base(d) + GIC_DIST_TARGET + (gic_irq(d) & ~3); - unsigned int cpu, shift = (gic_irq(d) % 4) * 8; - u32 val, mask, bit; - unsigned long flags; + void __iomem *reg = gic_dist_base(d) + GIC_DIST_TARGET + gic_irq(d); + unsigned int cpu;

if (!force) cpu = cpumask_any_and(mask_val, cpu_online_mask); @@ -342,13 +340,7 @@ static int gic_set_affinity(struct irq_data *d, const struct cpumask *mask_val, if (cpu >= NR_GIC_CPU_IF || cpu >= nr_cpu_ids) return -EINVAL;

- gic_lock_irqsave(flags); - mask = 0xff << shift; - bit = gic_cpu_map[cpu] << shift; - val = readl_relaxed(reg) & ~mask; - writel_relaxed(val | bit, reg); - gic_unlock_irqrestore(flags); - + writeb_relaxed(gic_cpu_map[cpu], reg); irq_data_update_effective_affinity(d, cpumask_of(cpu));

return IRQ_SET_MASK_OK_DONE;