[PATCH v3 35/35] x86/kvm: Enable 15-bit extension when KVM_FEATURE_MSI_EXT_DEST_ID detected

David Woodhouse
2020-10-24T21:37:57Z

From: David Woodhouse <dwmw@amazon.co.uk>

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>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kernel/kvm.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 1c0f2560a41c..b82de2843814 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -740,6 +740,11 @@ static void __init kvm_apic_init(void)
#endif
}

+static bool __init kvm_msi_ext_dest_id(void)
+{
+ return kvm_para_has_feature(KVM_FEATURE_MSI_EXT_DEST_ID);
+}
+
static void __init kvm_init_platform(void)
{
kvmclock_init();
@@ -769,6 +774,7 @@ const __initconst struct hypervisor_x86 x86_hyper_kvm = {
.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,
#if defined(CONFIG_AMD_MEM_ENCRYPT)
.runtime.sev_es_hcall_prepare = kvm_sev_es_hcall_prepare,