From: David Woodhouse <dwmw@amazon.co.uk>
Date: Sat, 24 Oct 2020 21:35:35 +0000 (+0100)
Subject: x86/kvm: Enable 15-bit extension when KVM_FEATURE_MSI_EXT_DEST_ID detected
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=3b0c20ef1faacd177aa747a1e3fd9ac14b37e4f5;p=users%2Fdwmw2%2Flinux.git

x86/kvm: Enable 15-bit extension when KVM_FEATURE_MSI_EXT_DEST_ID detected

This allows the host to indicate that MSI emulation supports 15-bit
destination IDs, allowing up to 32768 CPUs without interrupt remapping.

cf. https://patchwork.kernel.org/patch/11816693/ for qemu

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Link: https://lore.kernel.org/r/20201024213535.443185-36-dwmw2@infradead.org

(cherry picked from commit 2e008ffe426f927b1697adb4ed10c1e419927ae4)
---

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 9663ba31347c2..32ea09bc82081 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -744,12 +744,18 @@ static void __init kvm_init_platform(void)
 	x86_platform.apic_post_init = kvm_apic_init;
 }
 
+static bool __init kvm_msi_ext_dest_id(void)
+{
+	return kvm_para_has_feature(KVM_FEATURE_MSI_EXT_DEST_ID);
+}
+
 const __initconst struct hypervisor_x86 x86_hyper_kvm = {
 	.name			= "KVM",
 	.detect			= kvm_detect,
 	.type			= X86_HYPER_KVM,
 	.init.guest_late_init	= kvm_guest_init,
 	.init.x2apic_available	= kvm_para_available,
+	.init.msi_ext_dest_id	= kvm_msi_ext_dest_id,
 	.init.init_platform	= kvm_init_platform,
 };