[PATCH] x86/kvm/hyper-v: Don't deactivate APICv unconditionally when Hyper-V SynIC enabled

junjiehua0xff
2020-11-05T09:13:26Z

From: Junjie Hua <junjiehua@tencent.com>

The current implementation of Hyper-V SynIC[1] request to deactivate
APICv when SynIC is enabled, since the AutoEOI feature of SynIC is not
compatible with APICv[2].

Actually, windows doesn't use AutoEOI if deprecating AutoEOI bit is set
(CPUID.40000004H:EAX[bit 9], HyperV-TLFS v6.0b section 2.4.5), we don't
need to disable APICv in this case.

[1] commit 5c919412fe61 ("kvm/x86: Hyper-V synthetic interrupt controller")
[2] https://patchwork.kernel.org/patch/7486761/

Signed-off-by: Junjie Hua <junjiehua@tencent.com>
---
arch/x86/kvm/hyperv.c | 18 +++++++++++++++++-
arch/x86/kvm/lapic.c | 3 +++
2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 5c7c406..9eee2da 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -899,6 +899,19 @@ void kvm_hv_vcpu_postcreate(struct kvm_vcpu *vcpu)
hv_vcpu->vp_index = kvm_vcpu_get_idx(vcpu);
}

+static bool kvm_hv_is_synic_autoeoi_deprecated(struct kvm_vcpu *vcpu)
+{
+ struct kvm_cpuid_entry2 *entry;
+
+ entry = kvm_find_cpuid_entry(vcpu,
+ HYPERV_CPUID_ENLIGHTMENT_INFO,
+ 0);
+ if (!entry)
+ return false;
+
+ return entry->eax & HV_DEPRECATING_AEOI_RECOMMENDED;
+}
+
int kvm_hv_activate_synic(struct kvm_vcpu *vcpu, bool dont_zero_synic_pages)
{
struct kvm_vcpu_hv_synic *synic = vcpu_to_synic(vcpu);
@@ -908,7 +921,10 @@ int kvm_hv_activate_synic(struct kvm_vcpu *vcpu, bool dont_zero_synic_pages)
* not compatible with APICV, so request
* to deactivate APICV permanently.
*/
- kvm_request_apicv_update(vcpu->kvm, false, APICV_INHIBIT_REASON_HYPERV);
+ if (!kvm_hv_is_synic_autoeoi_deprecated(vcpu))
+ 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;
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 105e785..0bb431f 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1263,6 +1263,9 @@ void kvm_apic_set_eoi_accelerated(struct kvm_vcpu *vcpu, int vector)

trace_kvm_eoi(apic, vector);

+ if (test_bit(vector, vcpu_to_synic(apic->vcpu)->vec_bitmap))
+ kvm_hv_synic_send_eoi(apic->vcpu, vector);
+
kvm_ioapic_send_eoi(apic, vector);
kvm_make_request(KVM_REQ_EVENT, apic->vcpu);
}
--
1.8.3.1