linux-kernel - [PATCH 20/30] KVM: x86: hyper-v: Prepare to check access to Hyper-V hypercalls

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Message-Id: <20210419160127.192712-21-vkuznets@redhat.com>
Date:   Mon, 19 Apr 2021 18:01:17 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Siddharth Chandrasekaran <sidcha@...zon.de>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 20/30] KVM: x86: hyper-v: Prepare to check access to Hyper-V hypercalls

Introduce hv_check_hypercallr_access() to check if the particular hypercall
should be available to guest, this will be used with
KVM_CAP_HYPERV_ENFORCE_CPUID mode.

No functional change intended.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/kvm/hyperv.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 12b6803de1b7..4f0ab0c50c44 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -2022,6 +2022,11 @@ static u16 kvm_hvcall_signal_event(struct kvm_vcpu *vcpu, bool fast, u64 param)
 	return HV_STATUS_SUCCESS;
 }
 
+static bool hv_check_hypercall_access(struct kvm_vcpu_hv *hv_vcpu, u16 code)
+{
+	return true;
+}
+
 int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 {
 	u64 param, ingpa, outgpa, ret = HV_STATUS_SUCCESS;
@@ -2061,6 +2066,11 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 
 	trace_kvm_hv_hypercall(code, fast, rep_cnt, rep_idx, ingpa, outgpa);
 
+	if (unlikely(!hv_check_hypercall_access(to_hv_vcpu(vcpu), code))) {
+		ret = HV_STATUS_ACCESS_DENIED;
+		goto hypercall_complete;
+	}
+
 	switch (code) {
 	case HVCALL_NOTIFY_LONG_SPIN_WAIT:
 		if (unlikely(rep)) {
@@ -2167,6 +2177,7 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 		break;
 	}
 
+hypercall_complete:
 	return kvm_hv_hypercall_complete(vcpu, ret);
 }
 
-- 
2.30.2