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irqchip/gic-v4: Correctly deal with set_affinity on lazily-mapped VPEs

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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: 1442ee0011 ("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
This commit is contained in:
Marc Zyngier 2024-10-27 10:22:20 +00:00 committed by Thomas Gleixner
parent 5f994f5341
commit e6c24e2d05
1 changed files with 12 additions and 2 deletions
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14
drivers/irqchip/irq-gic-v3-its.c
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@ -3810,8 +3810,18 @@ static int its_vpe_set_affinity(struct irq_data *d,
* Check if we're racing against a VPE being destroyed, for
* which we don't want to allow a VMOVP.
*/
if (!atomic_read(&vpe->vmapp_count))
return -EINVAL;
if (!atomic_read(&vpe->vmapp_count)) {
if (gic_requires_eager_mapping())
return -EINVAL;
/*
* If we lazily map the VPEs, this isn't an error and
* we can exit cleanly.
*/
cpu = cpumask_first(mask_val);
irq_data_update_effective_affinity(d, cpumask_of(cpu));
return IRQ_SET_MASK_OK_DONE;
}
/*
* Changing affinity is mega expensive, so let's be as lazy as