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KVM: nVMX: Immediately refresh APICv controls as needed on nested VM-Exit

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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: 7c69661e22 ("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>
This commit is contained in:
Dongli Zhang
2025-12-05 15:19:05 -08:00
committed by Sean Christopherson
parent b2849bec93
commit 2976313883
1 changed files with 2 additions and 1 deletions
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3
arch/x86/kvm/vmx/nested.c
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@@ -19,6 +19,7 @@
#include "trace.h" #include "trace.h"
#include "vmx.h" #include "vmx.h"
#include "smm.h" #include "smm.h"
#include "x86_ops.h"
static bool __read_mostly enable_shadow_vmcs = 1; static bool __read_mostly enable_shadow_vmcs = 1;
module_param_named(enable_shadow_vmcs, enable_shadow_vmcs, bool, S_IRUGO); 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) { if (vmx->nested.update_vmcs01_apicv_status) {
vmx->nested.update_vmcs01_apicv_status = false; 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) { if (vmx->nested.update_vmcs01_hwapic_isr) {