linux-kernel - [PATCH v3 35/35] x86/kvm: Enable 15-bit extension when KVM_FEATURE_MSI_EXT_DEST

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Date:   Sat, 24 Oct 2020 22:35:35 +0100
From:   David Woodhouse <dwmw2@...radead.org>
To:     x86@...nel.org
Cc:     kvm <kvm@...r.kernel.org>, iommu@...ts.linux-foundation.org,
        joro@...tes.org, Thomas Gleixner <tglx@...utronix.de>,
        Paolo Bonzini <pbonzini@...hat.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-hyperv@...r.kernel.org, maz@...terjones.org,
        Dexuan Cui <decui@...rosoft.com>
Subject: [PATCH v3 35/35] x86/kvm: Enable 15-bit extension when KVM_FEATURE_MSI_EXT_DEST_ID detected

From: David Woodhouse <dwmw@...zon.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@...zon.co.uk>
Acked-by: Paolo Bonzini <pbonzini@...hat.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,
-- 
2.26.2