KVM: x86: hyper-v: Add helper to read hypercall data for array

Move the guts of kvm_get_sparse_vp_set() to a helper so that the code for
reading a guest-provided array can be reused in the future, e.g. for
getting a list of virtual addresses whose TLB entries need to be flushed.

Opportunisticaly swap the order of the data and XMM adjustment so that
the XMM/gpa offsets are bundled together.

No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20221101145426.251680-11-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/hyperv.c

@@ -1753,38 +1753,51 @@ struct kvm_hv_hcall {
 	sse128_t xmm[HV_HYPERCALL_MAX_XMM_REGISTERS];
 };
 
-static u64 kvm_get_sparse_vp_set(struct kvm *kvm, struct kvm_hv_hcall *hc,
-				 int consumed_xmm_halves,
-				 u64 *sparse_banks, gpa_t offset)
-{
-	u16 var_cnt;
-	int i;
 
-	if (hc->var_cnt > 64)
-		return -EINVAL;
-
-	/* Ignore banks that cannot possibly contain a legal VP index. */
-	var_cnt = min_t(u16, hc->var_cnt, KVM_HV_MAX_SPARSE_VCPU_SET_BITS);
+static int kvm_hv_get_hc_data(struct kvm *kvm, struct kvm_hv_hcall *hc,
+			      u16 orig_cnt, u16 cnt_cap, u64 *data,
+			      int consumed_xmm_halves, gpa_t offset)
+{
+	/*
+	 * Preserve the original count when ignoring entries via a "cap", KVM
+	 * still needs to validate the guest input (though the non-XMM path
+	 * punts on the checks).
+	 */
+	u16 cnt = min(orig_cnt, cnt_cap);
+	int i, j;
 
 	if (hc->fast) {
 		/*
 		 * Each XMM holds two sparse banks, but do not count halves that
 		 * have already been consumed for hypercall parameters.
 		 */
-		if (hc->var_cnt > 2 * HV_HYPERCALL_MAX_XMM_REGISTERS - consumed_xmm_halves)
+		if (orig_cnt > 2 * HV_HYPERCALL_MAX_XMM_REGISTERS - consumed_xmm_halves)
 			return HV_STATUS_INVALID_HYPERCALL_INPUT;
-		for (i = 0; i < var_cnt; i++) {
-			int j = i + consumed_xmm_halves;
+
+		for (i = 0; i < cnt; i++) {
+			j = i + consumed_xmm_halves;
 			if (j % 2)
-				sparse_banks[i] = sse128_hi(hc->xmm[j / 2]);
+				data[i] = sse128_hi(hc->xmm[j / 2]);
 			else
-				sparse_banks[i] = sse128_lo(hc->xmm[j / 2]);
+				data[i] = sse128_lo(hc->xmm[j / 2]);
 		}
 		return 0;
 	}
 
-	return kvm_read_guest(kvm, hc->ingpa + offset, sparse_banks,
-			      var_cnt * sizeof(*sparse_banks));
+	return kvm_read_guest(kvm, hc->ingpa + offset, data,
+			      cnt * sizeof(*data));
+}
+
+static u64 kvm_get_sparse_vp_set(struct kvm *kvm, struct kvm_hv_hcall *hc,
+				 u64 *sparse_banks, int consumed_xmm_halves,
+				 gpa_t offset)
+{
+	if (hc->var_cnt > 64)
+		return -EINVAL;
+
+	/* Cap var_cnt to ignore banks that cannot contain a legal VP index. */
+	return kvm_hv_get_hc_data(kvm, hc, hc->var_cnt, KVM_HV_MAX_SPARSE_VCPU_SET_BITS,
+				  sparse_banks, consumed_xmm_halves, offset);
 }
 
 static void hv_tlb_flush_enqueue(struct kvm_vcpu *vcpu)
@@ -1895,7 +1908,7 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
 		if (!hc->var_cnt)
 			goto ret_success;
 
-		if (kvm_get_sparse_vp_set(kvm, hc, 2, sparse_banks,
+		if (kvm_get_sparse_vp_set(kvm, hc, sparse_banks, 2,
 					  offsetof(struct hv_tlb_flush_ex,
 						   hv_vp_set.bank_contents)))
 			return HV_STATUS_INVALID_HYPERCALL_INPUT;
@@ -2006,7 +2019,7 @@ static u64 kvm_hv_send_ipi(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
 		if (!hc->var_cnt)
 			goto ret_success;
 
-		if (kvm_get_sparse_vp_set(kvm, hc, 1, sparse_banks,
+		if (kvm_get_sparse_vp_set(kvm, hc, sparse_banks, 1,
 					  offsetof(struct hv_send_ipi_ex,
 						   vp_set.bank_contents)))
 			return HV_STATUS_INVALID_HYPERCALL_INPUT;