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Commit 6b2875b5 authored by Jim Mattson's avatar Jim Mattson Committed by Greg Kroah-Hartman
Browse files

KVM: x86: Mask LVTPC when handling a PMI 



commit a16eb25b09c02a54c1c1b449d4b6cfa2cf3f013a upstream.

Per the SDM, "When the local APIC handles a performance-monitoring
counters interrupt, it automatically sets the mask flag in the LVT
performance counter register."  Add this behavior to KVM's local APIC
emulation.

Failure to mask the LVTPC entry results in spurious PMIs, e.g. when
running Linux as a guest, PMI handlers that do a "late_ack" spew a large
number of "dazed and confused" spurious NMI warnings.

Fixes: f5132b01 ("KVM: Expose a version 2 architectural PMU to a guests")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarJim Mattson <jmattson@google.com>
Tested-by: default avatarMingwei Zhang <mizhang@google.com>
Signed-off-by: default avatarMingwei Zhang <mizhang@google.com>
Link: https://lore.kernel.org/r/20230925173448.3518223-3-mizhang@google.com


[sean: massage changelog, correct Fixes]
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 1d434d83

arch/x86/kvm/lapic.c

+6 −2
Original line number Diff line number Diff line
@@ -2244,13 +2244,17 @@ int kvm_apic_local_deliver(struct kvm_lapic *apic, int lvt_type) 
{

	u32 reg = kvm_lapic_get_reg(apic, lvt_type);

	int vector, mode, trig_mode;

	int r;



	if (kvm_apic_hw_enabled(apic) && !(reg & APIC_LVT_MASKED)) {

		vector = reg & APIC_VECTOR_MASK;

		mode = reg & APIC_MODE_MASK;

		trig_mode = reg & APIC_LVT_LEVEL_TRIGGER;

		return __apic_accept_irq(apic, mode, vector, 1, trig_mode,

					NULL);



		r = __apic_accept_irq(apic, mode, vector, 1, trig_mode, NULL);

		if (r && lvt_type == APIC_LVTPC)

			kvm_lapic_set_reg(apic, APIC_LVTPC, reg | APIC_LVT_MASKED);

		return r;

	}

	return 0;

}