From e4b8828947b1135fba411f58cac123c85bb24093 Mon Sep 17 00:00:00 2001
From: Wei Hu <whu@FreeBSD.org>
Date: Mon, 11 Mar 2024 10:15:09 +0000
Subject: [PATCH] Hyper-V: vPCI: limit 64 cpus for msi/msix interrupt handling

On older Hyper-V vPCI protocol version 1.1, only the first 64 cpus
are able to handle msi/msix. This is true on FreeBSD 13.x and earlier
releases. If MSI IRQ is assigned to cpu id greater than 63, it would
lead to missing interrupts. Add check in set_interrupt_apic_ids() to
only add first 64 cpus into the interrupt cpu set.

Reported by:	NetApp
Tested by:	NetApp
Reviewed by:	kib
Sponsored by:	Microsoft
Differential Revision:	https://reviews.freebsd.org/D44297
---
 sys/x86/x86/mp_x86.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/sys/x86/x86/mp_x86.c b/sys/x86/x86/mp_x86.c
index 1f4caf07f979..56cf7e426076 100644
--- a/sys/x86/x86/mp_x86.c
+++ b/sys/x86/x86/mp_x86.c
@@ -1184,6 +1184,13 @@ set_interrupt_apic_ids(void)
 		    !hyperthreading_intr_allowed)
 			continue;
 
+		/*
+		 * Currently Hyper-V only supports intr on first
+		 * 64 cpus.
+		 */
+		if (vm_guest == VM_GUEST_HV && i > 63)
+			continue;
+
 		intr_add_cpu(i);
 	}
 }