x86/hyperv: Fix usage of cpu_online_mask to get valid cpu

Accessing cpu_online_mask here is problematic because the cpus read lock
is not held in this context.

However, cpu_online_mask isn't needed here since the effective affinity
mask is guaranteed to be valid in this callback. So, just use
cpumask_first() to get the cpu instead of ANDing it with cpus_online_mask
unnecessarily.

Fixes: e39397d ("x86/hyperv: implement an MSI domain for root partition")
Reported-by: Michael Kelley <[email protected]>
Closes: https://lore.kernel.org/linux-hyperv/SN6PR02MB4157639630F8AD2D8FD8F52FD475A@SN6PR02MB4157.namprd02.prod.outlook.com/
Suggested-by: Thomas Gleixner <[email protected]>
Signed-off-by: Nuno Das Neves <[email protected]>
Reviewed-by: Michael Kelley <[email protected]>
Link: https://lore.kernel.org/r/1751582677-30930-4-git-send-email-nunodasneves@linux.microsoft.com
Signed-off-by: Wei Liu <[email protected]>
Message-ID: <1751582677-30930-4-git-send-email-nunodasneves@linux.microsoft.com>

Author: NunoDasNeves

arch/x86/hyperv/irqdomain.c

@@ -193,7 +193,6 @@ static void hv_irq_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
 	struct pci_dev *dev;
 	struct hv_interrupt_entry out_entry, *stored_entry;
 	struct irq_cfg *cfg = irqd_cfg(data);
-	const cpumask_t *affinity;
 	int cpu;
 	u64 status;
 
@@ -205,8 +204,7 @@ static void hv_irq_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
 		return;
 	}
 
-	affinity = irq_data_get_effective_affinity_mask(data);
-	cpu = cpumask_first_and(affinity, cpu_online_mask);
+	cpu = cpumask_first(irq_data_get_effective_affinity_mask(data));
 
 	if (data->chip_data) {
 		/*