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Marc ZyngierKAGA-KOKO
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irqchip/gic-v4: Correctly deal with set_affinity on lazily-mapped VPEs
Zenghui points out that a recent change to the way set_affinity is handled for VPEs has the potential to return an error if the VPE hasn't been mapped yet (because the guest hasn't emited a MAPTI command yet), affecting GICv4.0 implementations that rely on the ITSList feature. Fix this by making the set_affinity succeed in this case, and return early, without trying to touch the HW. Fixes: 1442ee0 ("irqchip/gic-v4: Don't allow a VMOVP on a dying VPE") Reported-by: Zenghui Yu <yuzenghui@huawei.com> Signed-off-by: Marc Zyngier <maz@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Zenghui Yu <yuzenghui@huawei.com> Link: https://lore.kernel.org/all/20241027102220.1858558-1-maz@kernel.org Link: https://lore.kernel.org/r/aab45cd3-e5ca-58cf-e081-e32a17f5b4e7@huawei.com
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drivers/irqchip/irq-gic-v3-its.c

Lines changed: 12 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -3810,8 +3810,18 @@ static int its_vpe_set_affinity(struct irq_data *d,
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* Check if we're racing against a VPE being destroyed, for
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* which we don't want to allow a VMOVP.
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*/
3813-
if (!atomic_read(&vpe->vmapp_count))
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return -EINVAL;
3813+
if (!atomic_read(&vpe->vmapp_count)) {
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if (gic_requires_eager_mapping())
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return -EINVAL;
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/*
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* If we lazily map the VPEs, this isn't an error and
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* we can exit cleanly.
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*/
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cpu = cpumask_first(mask_val);
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irq_data_update_effective_affinity(d, cpumask_of(cpu));
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return IRQ_SET_MASK_OK_DONE;
3824+
}
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/*
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* Changing affinity is mega expensive, so let's be as lazy as

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