linux-kernel - [PATCH 5.7 216/265] kvm: lapic: fix broken vcpu hotplug

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Date:   Mon, 29 Jun 2020 11:17:29 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Igor Mammedov <imammedo@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: [PATCH 5.7 216/265] kvm: lapic: fix broken vcpu hotplug

From: Igor Mammedov <imammedo@...hat.com>

commit af28dfacbe00d53df5dec2bf50640df33138b1fe upstream.

Guest fails to online hotplugged CPU with error
  smpboot: do_boot_cpu failed(-1) to wakeup CPU#4

It's caused by the fact that kvm_apic_set_state(), which used to call
recalculate_apic_map() unconditionally and pulled hotplugged CPU into
apic map, is updating map conditionally on state changes.  In this case
the APIC map is not considered dirty and the is not updated.

Fix the issue by forcing unconditional update from kvm_apic_set_state(),
like it used to be.

Fixes: 4abaffce4d25a ("KVM: LAPIC: Recalculate apic map in batch")
Cc: stable@...r.kernel.org
Signed-off-by: Igor Mammedov <imammedo@...hat.com>
Message-Id: <20200622160830.426022-1-imammedo@...hat.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/x86/kvm/lapic.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 9af25c97612a7..8967e320a9784 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -2512,6 +2512,7 @@ int kvm_apic_set_state(struct kvm_vcpu *vcpu, struct kvm_lapic_state *s)
 	}
 	memcpy(vcpu->arch.apic->regs, s->regs, sizeof(*s));
 
+	apic->vcpu->kvm->arch.apic_map_dirty = true;
 	kvm_recalculate_apic_map(vcpu->kvm);
 	kvm_apic_set_version(vcpu);
 
-- 
2.25.1