5.15-stable review patch. If anyone has any objections, please let me know.
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From: Marc Zyngier maz@kernel.org
commit af9acbfc2c4b72c378d0b9a2ee023ed01055d3e2 upstream.
When updating the affinity of a VPE, the VMOVP command is currently skipped if the two CPUs are part of the same VPE affinity.
But this is wrong, as the doorbell corresponding to this VPE is still delivered on the 'old' CPU, which screws up the balancing. Furthermore, offlining that 'old' CPU results in doorbell interrupts generated for this VPE being discarded.
The harsh reality is that VMOVP cannot be elided when a set_affinity() request occurs. It needs to be obeyed, and if an optimisation is to be made, it is at the point where the affinity change request is made (such as in KVM).
Drop the VMOVP elision altogether, and only use the vpe_table_mask to try and stay within the same ITS affinity group if at all possible.
Fixes: dd3f050a216e (irqchip/gic-v4.1: Implement the v4.1 flavour of VMOVP) Reported-by: Kunkun Jiang jiangkunkun@huawei.com Signed-off-by: Marc Zyngier maz@kernel.org Signed-off-by: Thomas Gleixner tglx@linutronix.de Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20240213101206.2137483-4-maz@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/irqchip/irq-gic-v3-its.c | 22 +++++++++++++--------- 1 file changed, 13 insertions(+), 9 deletions(-)
--- a/drivers/irqchip/irq-gic-v3-its.c +++ b/drivers/irqchip/irq-gic-v3-its.c @@ -3800,8 +3800,9 @@ static int its_vpe_set_affinity(struct i bool force) { struct its_vpe *vpe = irq_data_get_irq_chip_data(d); - int from, cpu = cpumask_first(mask_val); + struct cpumask common, *table_mask; unsigned long flags; + int from, cpu;
/* * Changing affinity is mega expensive, so let's be as lazy as @@ -3817,19 +3818,22 @@ static int its_vpe_set_affinity(struct i * taken on any vLPI handling path that evaluates vpe->col_idx. */ from = vpe_to_cpuid_lock(vpe, &flags); - if (from == cpu) - goto out; - - vpe->col_idx = cpu; + table_mask = gic_data_rdist_cpu(from)->vpe_table_mask;
/* - * GICv4.1 allows us to skip VMOVP if moving to a cpu whose RD - * is sharing its VPE table with the current one. + * If we are offered another CPU in the same GICv4.1 ITS + * affinity, pick this one. Otherwise, any CPU will do. */ - if (gic_data_rdist_cpu(cpu)->vpe_table_mask && - cpumask_test_cpu(from, gic_data_rdist_cpu(cpu)->vpe_table_mask)) + if (table_mask && cpumask_and(&common, mask_val, table_mask)) + cpu = cpumask_test_cpu(from, &common) ? from : cpumask_first(&common); + else + cpu = cpumask_first(mask_val); + + if (from == cpu) goto out;
+ vpe->col_idx = cpu; + its_send_vmovp(vpe); its_vpe_db_proxy_move(vpe, from, cpu);