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 9663ba31347c20141e4d1806731f2e8512239c52..32ea09bc820813dc387d2c9d0754143e90dd4426 100644 (file)
--- 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,
 };