KVM: nVMX: Do not load EOI-exitmap while running L2

When L1 IOAPIC redirection-table is written, a request of
KVM_REQ_SCAN_IOAPIC is set on all vCPUs. This is done such that
all vCPUs will now recalc their IOAPIC handled vectors and load
it to their EOI-exitmap.

However, it could be that one of the vCPUs is currently running
L2. In this case, load_eoi_exitmap() will be called which would
write to vmcs02->eoi_exit_bitmap, which is wrong because
vmcs02->eoi_exit_bitmap should always be equal to
vmcs12->eoi_exit_bitmap. Furthermore, at this point
KVM_REQ_SCAN_IOAPIC was already consumed and therefore we will
never update vmcs01->eoi_exit_bitmap. This could lead to remote_irr
of some IOAPIC level-triggered entry to remain set forever.

Fix this issue by delaying the load of EOI-exitmap to when vCPU
is running L1.

One may wonder why not just delay entire KVM_REQ_SCAN_IOAPIC
processing to when vCPU is running L1. This is done in order to handle
correctly the case where LAPIC & IO-APIC of L1 is pass-throughed into
L2. In this case, vmcs12->virtual_interrupt_delivery should be 0. In
current nVMX implementation, that results in
vmcs02->virtual_interrupt_delivery to also be 0. Thus,
vmcs02->eoi_exit_bitmap is not used. Therefore, every L2 EOI cause
a #VMExit into L0 (either on MSR_WRITE to x2APIC MSR or
APIC_ACCESS/APIC_WRITE/EPT_MISCONFIG to APIC MMIO page).
In order for such L2 EOI to be broadcasted, if needed, from LAPIC
to IO-APIC, vcpu->arch.ioapic_handled_vectors must be updated
while L2 is running. Therefore, patch makes sure to delay only the
loading of EOI-exitmap but not the update of
vcpu->arch.ioapic_handled_vectors.

Reviewed-by: Arbel Moshe <arbel.moshe@oracle.com>
Reviewed-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
Signed-off-by: Liran Alon <liran.alon@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 8fb60287d987..c72891dd7d78 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -73,6 +73,7 @@
 #define KVM_REQ_HV_RESET		KVM_ARCH_REQ(20)
 #define KVM_REQ_HV_EXIT			KVM_ARCH_REQ(21)
 #define KVM_REQ_HV_STIMER		KVM_ARCH_REQ(22)
+#define KVM_REQ_LOAD_EOI_EXITMAP	KVM_ARCH_REQ(23)
 
 #define CR0_RESERVED_BITS                                               \
 	(~(unsigned long)(X86_CR0_PE | X86_CR0_MP | X86_CR0_EM | X86_CR0_TS \
@@ -498,6 +499,7 @@ struct kvm_vcpu_arch {
 	u64 apic_base;
 	struct kvm_lapic *apic;    /* kernel irqchip context */
 	bool apicv_active;
+	bool load_eoi_exitmap_pending;
 	DECLARE_BITMAP(ioapic_handled_vectors, 256);
 	unsigned long apic_attention;
 	int32_t apic_arb_prio;