From e1fc9911e85251004306fd462b48a6063ca0c3aa Mon Sep 17 00:00:00 2001
From: Petr Pavlu <petr.pavlu@suse.com>
Date: Thu, 17 Jun 2021 17:58:52 +0200
Subject: [PATCH] PCI: hv: Use expected affinity when unmasking IRQ
Patch-mainline: Never, fix for use of effective affinity
References: bsc#1185973

Function hv_irq_unmask() in the Hyper-V PCIe MSI driver relies on
a SLE-specific implementation of irq_data_get_effective_affinity_mask()
(patches.suse/irq_data_get_effective_affinity_mask.patch) and uses its
result to unmask a given IRQ on specific CPUs. A problem is that
irq_data_get_effective_affinity_mask() can incorrectly return an
effective mask that is not a subset of the originally requested
affinity. Specifically, if a machine uses the flat APIC driver then the
effective affinity returned by irq_data_get_effective_affinity_mask() is
always 0xff. The result is that hv_irq_unmask() can unmask the IRQ on
a wrong CPU.

Fixing irq_data_get_effective_affinity_mask() would require bringing in
more backports to implement the functionality properly. However, since
the function is used only by the Hyper-V PCIe MSI driver, a minimum fix
is to correct the problem there by additionally doing intersection with
the original affinity.

Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
---
 drivers/pci/host/pci-hyperv.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
index ccdc7d4b72a6..dd15c3f4057d 100644
--- a/drivers/pci/host/pci-hyperv.c
+++ b/drivers/pci/host/pci-hyperv.c
@@ -973,6 +973,7 @@ static void hv_irq_unmask(struct irq_data *data)
 		}
 
 		cpumask_and(tmp, dest, cpu_online_mask);
+		cpumask_and(tmp, tmp, irq_data_get_affinity_mask(data));
 		nr_bank = cpumask_to_vpset(&params->int_target.vp_set, tmp);
 		free_cpumask_var(tmp);
 
-- 
2.26.2