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[v5,08/33] KVM: x86: Handle APICv updates for APIC "mode" changes via request

Message ID 20230106011306.85230-9-seanjc@google.com
State New
Headers
Series KVM: x86: AVIC and local APIC fixes+cleanups |

Commit Message

Sean Christopherson Jan. 6, 2023, 1:12 a.m. UTC 
  Use KVM_REQ_UPDATE_APICV to react to APIC "mode" changes, i.e. to handle
the APIC being hardware enabled/disabled and/or x2APIC being toggled.
There is no need to immediately update APICv state, the only requirement
is that APICv be updating prior to the next VM-Enter.

Making a request will allow piggybacking KVM_REQ_UPDATE_APICV to "inhibit"
the APICv memslot when x2APIC is enabled.  Doing that directly from
kvm_lapic_set_base() isn't feasible as KVM's SRCU must not be held when
modifying memslots (to avoid deadlock), and may or may not be held when
kvm_lapic_set_base() is called, i.e. KVM can't do the right thing without
tracking that is rightly buried behind CONFIG_PROVE_RCU=y.

Suggested-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/lapic.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
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Patch

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 2183a9b8efa5..3ed74ad60516 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -2401,7 +2401,7 @@  void kvm_lapic_set_base(struct kvm_vcpu *vcpu, u64 value)
 		kvm_apic_set_x2apic_id(apic, vcpu->vcpu_id);
 
 	if ((old_value ^ value) & (MSR_IA32_APICBASE_ENABLE | X2APIC_ENABLE)) {
-		kvm_vcpu_update_apicv(vcpu);
+		kvm_make_request(KVM_REQ_APICV_UPDATE, vcpu);
 		static_call_cond(kvm_x86_set_virtual_apic_mode)(vcpu);
 	}