[PATCH RFC 21/22] KVM: x86: hyper-v: Honor HV_X64_CLUSTER_IPI_RECOMMENDED bit

[Vitaly Kuznetsov]

Hyper-V partition must possess 'HV_X64_CLUSTER_IPI_RECOMMENDED'
privilege ('recommended' is rather a misnomer) to issue
HVCALL_SEND_IPI hypercalls. 'HVCALL_SEND_IPI_EX' version of the
hypercall also requires HV_X64_EX_PROCESSOR_MASKS_RECOMMENDED.

Signed-off-by: Vitaly Kuznetsov <vkuzn...@redhat.com>
---
 arch/x86/kvm/hyperv.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 3e8a34c08aef..37b8ff30fc1d 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -2211,6 +2211,12 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
                ret = kvm_hv_flush_tlb(vcpu, ingpa, rep_cnt, true);
                break;
        case HVCALL_SEND_IPI:
+               if (unlikely(!(hv_vcpu->cpuid_cache.enlightenments_eax &
+                              HV_X64_CLUSTER_IPI_RECOMMENDED))) {
+                       ret = HV_STATUS_ACCESS_DENIED;
+                       break;
+               }
+
                if (unlikely(rep)) {
                        ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
                        break;
@@ -2218,6 +2224,14 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
                ret = kvm_hv_send_ipi(vcpu, ingpa, outgpa, false, fast);
                break;
        case HVCALL_SEND_IPI_EX:
+               if (unlikely(!(hv_vcpu->cpuid_cache.enlightenments_eax &
+                              HV_X64_CLUSTER_IPI_RECOMMENDED) ||
+                            !(hv_vcpu->cpuid_cache.enlightenments_eax &
+                              HV_X64_EX_PROCESSOR_MASKS_RECOMMENDED))) {
+                       ret = HV_STATUS_ACCESS_DENIED;
+                       break;
+               }
+
                if (unlikely(fast || rep)) {
                        ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
                        break;
-- 
2.30.2