The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x 29763138830916f46daaa50e83e7f4f907a3236b # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025122917-cadet-worrier-23c0@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 29763138830916f46daaa50e83e7f4f907a3236b Mon Sep 17 00:00:00 2001 From: Dongli Zhang dongli.zhang@oracle.com Date: Fri, 5 Dec 2025 15:19:05 -0800 Subject: [PATCH] KVM: nVMX: Immediately refresh APICv controls as needed on nested VM-Exit

If an APICv status updated was pended while L2 was active, immediately refresh vmcs01's controls instead of pending KVM_REQ_APICV_UPDATE as kvm_vcpu_update_apicv() only calls into vendor code if a change is necessary.

E.g. if APICv is inhibited, and then activated while L2 is running:

kvm_vcpu_update_apicv() | -> __kvm_vcpu_update_apicv() | -> apic->apicv_active = true | -> vmx_refresh_apicv_exec_ctrl() | -> vmx->nested.update_vmcs01_apicv_status = true | -> return

Then L2 exits to L1:

__nested_vmx_vmexit() | -> kvm_make_request(KVM_REQ_APICV_UPDATE)

vcpu_enter_guest(): KVM_REQ_APICV_UPDATE -> kvm_vcpu_update_apicv() | -> __kvm_vcpu_update_apicv() | -> return // because if (apic->apicv_active == activate)

Reported-by: Chao Gao chao.gao@intel.com Closes: https://lore.kernel.org/all/aQ2jmnN8wUYVEawF@intel.com Fixes: 7c69661e225c ("KVM: nVMX: Defer APICv updates while L2 is active until L1 is active") Cc: stable@vger.kernel.org Signed-off-by: Dongli Zhang dongli.zhang@oracle.com [sean: write changelog] Link: https://patch.msgid.link/20251205231913.441872-3-seanjc@google.com Signed-off-by: Sean Christopherson seanjc@google.com

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index bcea087b642f..1725c6a94f99 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -19,6 +19,7 @@ #include "trace.h" #include "vmx.h" #include "smm.h" +#include "x86_ops.h"

static bool __read_mostly enable_shadow_vmcs = 1; module_param_named(enable_shadow_vmcs, enable_shadow_vmcs, bool, S_IRUGO); @@ -5216,7 +5217,7 @@ void __nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 vm_exit_reason,

if (vmx->nested.update_vmcs01_apicv_status) { vmx->nested.update_vmcs01_apicv_status = false; - kvm_make_request(KVM_REQ_APICV_UPDATE, vcpu); + vmx_refresh_apicv_exec_ctrl(vcpu); }

if (vmx->nested.update_vmcs01_hwapic_isr) {