[PATCH 1/2] KVM: PPC: Book3S HV: check caller of H_SVM_* Hcalls

[Laurent Dufour]

The Hcall named H_SVM_* are reserved to the Ultravisor. However, nothing
prevent a malicious VM or SVM to call them. This could lead to weird result
and should be filtered out.

Checking the Secure bit of the calling MSR ensure that the call is coming
from either the Ultravisor or a SVM. But any system call made from a SVM
are going through the Ultravisor, and the Ultravisor should filter out
these malicious call. This way, only the Ultravisor is able to make such a
Hcall.

Cc: Bharata B Rao <bharata at linux.ibm.com>
Cc: Paul Mackerras <paulus at ozlabs.org>
Cc: Benjamin Herrenschmidt <benh at kernel.crashing.org>
Cc: Michael Ellerman <mpe at ellerman.id.au>
Signed-off-by: Laurent Dufour <ldufour at linux.ibm.com>
---
 arch/powerpc/kvm/book3s_hv.c | 32 +++++++++++++++++++++-----------
 1 file changed, 21 insertions(+), 11 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 33be4d93248a..43773182a737 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -1074,25 +1074,35 @@ int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu)
 					 kvmppc_get_gpr(vcpu, 6));
 		break;
 	case H_SVM_PAGE_IN:
-		ret = kvmppc_h_svm_page_in(vcpu->kvm,
-					   kvmppc_get_gpr(vcpu, 4),
-					   kvmppc_get_gpr(vcpu, 5),
-					   kvmppc_get_gpr(vcpu, 6));
+		ret = H_UNSUPPORTED;
+		if (kvmppc_get_srr1(vcpu) & MSR_S)
+			ret = kvmppc_h_svm_page_in(vcpu->kvm,
+						   kvmppc_get_gpr(vcpu, 4),
+						   kvmppc_get_gpr(vcpu, 5),
+						   kvmppc_get_gpr(vcpu, 6));
 		break;
 	case H_SVM_PAGE_OUT:
-		ret = kvmppc_h_svm_page_out(vcpu->kvm,
-					    kvmppc_get_gpr(vcpu, 4),
-					    kvmppc_get_gpr(vcpu, 5),
-					    kvmppc_get_gpr(vcpu, 6));
+		ret = H_UNSUPPORTED;
+		if (kvmppc_get_srr1(vcpu) & MSR_S)
+			ret = kvmppc_h_svm_page_out(vcpu->kvm,
+						    kvmppc_get_gpr(vcpu, 4),
+						    kvmppc_get_gpr(vcpu, 5),
+						    kvmppc_get_gpr(vcpu, 6));
 		break;
 	case H_SVM_INIT_START:
-		ret = kvmppc_h_svm_init_start(vcpu->kvm);
+		ret = H_UNSUPPORTED;
+		if (kvmppc_get_srr1(vcpu) & MSR_S)
+			ret = kvmppc_h_svm_init_start(vcpu->kvm);
 		break;
 	case H_SVM_INIT_DONE:
-		ret = kvmppc_h_svm_init_done(vcpu->kvm);
+		ret = H_UNSUPPORTED;
+		if (kvmppc_get_srr1(vcpu) & MSR_S)
+			ret = kvmppc_h_svm_init_done(vcpu->kvm);
 		break;
 	case H_SVM_INIT_ABORT:
-		ret = kvmppc_h_svm_init_abort(vcpu->kvm);
+		ret = H_UNSUPPORTED;
+		if (kvmppc_get_srr1(vcpu) & MSR_S)
+			ret = kvmppc_h_svm_init_abort(vcpu->kvm);
 		break;
 
 	default:
-- 
2.25.2