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KVM: x86: Handle APICv updates for APIC "mode" changes via request

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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>
Message-Id: <20230106011306.85230-9-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2023-01-06 01:12:41 +00:00 committed by Paolo Bonzini
parent e0bead97e7
commit 1459f5c6b8
1 changed files with 1 additions and 1 deletions
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2
arch/x86/kvm/lapic.c
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@ -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);
}