FAILED: patch "[PATCH] KVM: nVMX: Immediately refresh APICv controls as needed on" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-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 <[email protected]>.

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-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 29763138830916f46daaa50e83e7f4f907a3236b
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025122927-delegate-composed-5765@gregkh' --subject-prefix 'PATCH 5.15.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 <[email protected]>
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)

index bcea087b642f..1725c6a94f99 100644
@@ -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) {

From: Dongli Zhang <[email protected]>

[ Upstream commit 29763138830916f46daaa50e83e7f4f907a3236b ]

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)

---
 arch/x86/kvm/vmx/nested.c | 2 +-
 arch/x86/kvm/vmx/vmx.c    | 2 +-
 arch/x86/kvm/vmx/vmx.h    | 1 +
 3 files changed, 3 insertions(+), 2 deletions(-)

index e28f52f525e0..70b55267ea71 100644
@@ -4684,7 +4684,7 @@ 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 ((vm_exit_reason != -1) &&

index ab3098ea4ebd..cc8e4bc596ff 100644
@@ -4217,7 +4217,7 @@ static u32 vmx_vmexit_ctrl(void)
 		~(VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL | VM_EXIT_LOAD_IA32_EFER);
 }
 
-static void vmx_refresh_apicv_exec_ctrl(struct kvm_vcpu *vcpu)
+void vmx_refresh_apicv_exec_ctrl(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 

index a1792d96618a..9842f6833929 100644
@@ -386,6 +386,7 @@ void __vmx_set_segment(struct kvm_vcpu *vcpu, struct kvm_segment *var, int seg);
 u64 construct_eptp(struct kvm_vcpu *vcpu, hpa_t root_hpa, int root_level);
 
 bool vmx_guest_inject_ac(struct kvm_vcpu *vcpu);
+void vmx_refresh_apicv_exec_ctrl(struct kvm_vcpu *vcpu);
 void vmx_update_exception_bitmap(struct kvm_vcpu *vcpu);
 bool vmx_nmi_blocked(struct kvm_vcpu *vcpu);
 bool __vmx_interrupt_blocked(struct kvm_vcpu *vcpu);

2.51.0