KVM: x86: hyper-v: Check access to hypercall before reading XMM registers

In case guest doesn't have access to the particular hypercall we can avoid
reading XMM registers.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Siddharth Chandrasekaran <sidcha@amazon.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210730122625.112848-2-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index b07592c..cb7e045 100644 (file)
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -2173,9 +2173,6 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
        hc.rep_idx = (hc.param >> HV_HYPERCALL_REP_START_OFFSET) & 0xfff;
        hc.rep = !!(hc.rep_cnt || hc.rep_idx);
 
-       if (hc.fast && is_xmm_fast_hypercall(&hc))
-               kvm_hv_hypercall_read_xmm(&hc);
-
        trace_kvm_hv_hypercall(hc.code, hc.fast, hc.rep_cnt, hc.rep_idx,
                               hc.ingpa, hc.outgpa);
 
@@ -2184,6 +2181,9 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
                goto hypercall_complete;
        }
 
+       if (hc.fast && is_xmm_fast_hypercall(&hc))
+               kvm_hv_hypercall_read_xmm(&hc);
+
        switch (hc.code) {
        case HVCALL_NOTIFY_LONG_SPIN_WAIT:
                if (unlikely(hc.rep)) {