APICV_INHIBIT_REASON_HYPERV is currently unconditionally forced upon
SynIC activation as SynIC's AutoEOI is incompatible with APICv/AVIC. It is,
however, possible to track whether the feature was actually used by the
guest and only inhibit APICv/AVIC when needed.
TLFS suggests a dedicated 'HV_DEPRECATING_AEOI_RECOMMENDED' flag to let
Windows know that AutoEOI feature should be avoided. While it's up to
KVM userspace to set the flag, KVM can help a bit by exposing global
APICv/AVIC enablement: in case APICv/AVIC usage is impossible, AutoEOI
is still preferred.
Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
---
arch/x86/include/asm/kvm_host.h | 7 +++++
arch/x86/kvm/hyperv.c | 51 +++++++++++++++++++++++++++++----
2 files changed, 52 insertions(+), 6 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index ed4e2aae13d1..01ee8f29d6e3 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -91,6 +91,8 @@
#define KVM_REQ_MSR_FILTER_CHANGED KVM_ARCH_REQ(29)
#define KVM_REQ_UPDATE_CPU_DIRTY_LOGGING \
KVM_ARCH_REQ_FLAGS(30, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
+#define KVM_REQ_APICV_INPROGRESS \
+ KVM_ARCH_REQ_FLAGS(31, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
#define CR0_RESERVED_BITS \
(~(unsigned long)(X86_CR0_PE | X86_CR0_MP | X86_CR0_EM | X86_CR0_TS \
@@ -936,8 +938,13 @@ struct kvm_hv {
/* How many vCPUs have VP index != vCPU index */
atomic_t num_mismatched_vp_indexes;
+ /* How many SynICs use 'AutoEOI' feature */
+ atomic_t synic_auto_eoi_used;
+
struct hv_partition_assist_pg *hv_pa_pg;
struct kvm_hv_syndbg hv_syndbg;
+
+ struct work_struct apic_update_work;
};
struct msr_bitmap_range {
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index f00830e5202f..08cfc9ec1ef2 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -84,9 +84,32 @@ static bool synic_has_vector_auto_eoi(struct kvm_vcpu_hv_synic *synic,
return false;
}
+static void hv_apicv_update_work(struct work_struct *work)
+{
+ struct kvm_hv *hv = container_of(work, struct kvm_hv,
+ apic_update_work);
+ struct kvm_arch *ka = container_of(hv, struct kvm_arch,
+ hyperv);
+ struct kvm *kvm = container_of(ka, struct kvm, arch);
+ struct kvm_vcpu *vcpu;
+ int i;
+
+ mutex_lock(&kvm->lock);
+ kvm_request_apicv_update(kvm, atomic_read(&hv->synic_auto_eoi_used) == 0,
+ APICV_INHIBIT_REASON_HYPERV);
+ kvm_for_each_vcpu(i, vcpu, kvm)
+ kvm_clear_request(KVM_REQ_APICV_INPROGRESS, vcpu);
+ mutex_unlock(&kvm->lock);
+}
+
static void synic_update_vector(struct kvm_vcpu_hv_synic *synic,
int vector)
{
+ struct kvm_vcpu *vcpu = hv_synic_to_vcpu(synic);
+ struct kvm_hv *hv = to_kvm_hv(vcpu->kvm);
+ int auto_eoi_old, auto_eoi_new;
+ bool apicv_update_needed = false;
+
if (vector < HV_SYNIC_FIRST_VALID_VECTOR)
return;
@@ -95,10 +118,28 @@ static void synic_update_vector(struct kvm_vcpu_hv_synic *synic,
else
__clear_bit(vector, synic->vec_bitmap);
+ auto_eoi_old = bitmap_weight(synic->auto_eoi_bitmap, 256);
+
if (synic_has_vector_auto_eoi(synic, vector))
__set_bit(vector, synic->auto_eoi_bitmap);
else
__clear_bit(vector, synic->auto_eoi_bitmap);
+
+ auto_eoi_new = bitmap_weight(synic->auto_eoi_bitmap, 256);
+
+ /* Hyper-V SynIC auto EOI SINTs are not compatible with APICv */
+ if (!auto_eoi_old && auto_eoi_new) {
+ if (atomic_inc_return(&hv->synic_auto_eoi_used) == 1)
+ apicv_update_needed = true;
+ } else if (!auto_eoi_new && auto_eoi_old) {
+ if (atomic_dec_return(&hv->synic_auto_eoi_used) == 0)
+ apicv_update_needed = true;
+ }
+
+ if (apicv_update_needed) {
+ kvm_make_all_cpus_request(vcpu->kvm, KVM_REQ_APICV_INPROGRESS);
+ schedule_work(&hv->apic_update_work);
+ }
}
static int synic_set_sint(struct kvm_vcpu_hv_synic *synic, int sint,
@@ -931,12 +972,6 @@ int kvm_hv_activate_synic(struct kvm_vcpu *vcpu, bool dont_zero_synic_pages)
synic = to_hv_synic(vcpu);
- /*
- * Hyper-V SynIC auto EOI SINT's are
- * not compatible with APICV, so request
- * to deactivate APICV permanently.
- */
- kvm_request_apicv_update(vcpu->kvm, false, APICV_INHIBIT_REASON_HYPERV);
synic->active = true;
synic->dont_zero_synic_pages = dont_zero_synic_pages;
synic->control = HV_SYNIC_CONTROL_ENABLE;
@@ -2041,6 +2076,7 @@ void kvm_hv_init_vm(struct kvm *kvm)
mutex_init(&hv->hv_lock);
idr_init(&hv->conn_to_evt);
+ INIT_WORK(&hv->apic_update_work, hv_apicv_update_work);
}
void kvm_hv_destroy_vm(struct kvm *kvm)
@@ -2052,6 +2088,7 @@ void kvm_hv_destroy_vm(struct kvm *kvm)
idr_for_each_entry(&hv->conn_to_evt, eventfd, i)
eventfd_ctx_put(eventfd);
idr_destroy(&hv->conn_to_evt);
+ cancel_work_sync(&hv->apic_update_work);
}
static int kvm_hv_eventfd_assign(struct kvm *kvm, u32 conn_id, int fd)
@@ -2206,6 +2243,8 @@ int kvm_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
ent->eax |= HV_X64_ENLIGHTENED_VMCS_RECOMMENDED;
if (!cpu_smt_possible())
ent->eax |= HV_X64_NO_NONARCH_CORESHARING;
+ if (enable_apicv)
+ ent->eax |= HV_DEPRECATING_AEOI_RECOMMENDED;
/*
* Default number of spinlock retry attempts, matches
* HyperV 2016.
--
2.31.1
