[PATCH 2/3] kvm-s390: Fix problem state check for b2 intercepts

[Christian Borntraeger <borntraeger@de.ibm.com>]

From: Christian Borntraeger <borntraeger@de.ibm.com>

The kernel handles some priviledged instruction exits. While I was
unable to trigger such an exit from guest userspace, the code should
check for supervisor state before emulating a priviledged instruction.

I also renamed kvm_s390_handle_priv to kvm_s390_handle_b2. After all
there are non priviledged b2 instructions like stck (store clock).

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
---
 arch/s390/kvm/intercept.c |    2 +-
 arch/s390/kvm/kvm-s390.h  |    2 +-
 arch/s390/kvm/priv.c      |   18 +++++++++++++++---
 3 files changed, 17 insertions(+), 5 deletions(-)

Index: kvm/arch/s390/kvm/intercept.c
===================================================================
--- kvm.orig/arch/s390/kvm/intercept.c
+++ kvm/arch/s390/kvm/intercept.c
@@ -103,7 +103,7 @@ static int handle_lctl(struct kvm_vcpu *
 static intercept_handler_t instruction_handlers[256] = {
 	[0x83] = kvm_s390_handle_diag,
 	[0xae] = kvm_s390_handle_sigp,
-	[0xb2] = kvm_s390_handle_priv,
+	[0xb2] = kvm_s390_handle_b2,
 	[0xb7] = handle_lctl,
 	[0xeb] = handle_lctlg,
 };
Index: kvm/arch/s390/kvm/kvm-s390.h
===================================================================
--- kvm.orig/arch/s390/kvm/kvm-s390.h
+++ kvm/arch/s390/kvm/kvm-s390.h
@@ -50,7 +50,7 @@ int kvm_s390_inject_vcpu(struct kvm_vcpu
 int kvm_s390_inject_program_int(struct kvm_vcpu *vcpu, u16 code);
 
 /* implemented in priv.c */
-int kvm_s390_handle_priv(struct kvm_vcpu *vcpu);
+int kvm_s390_handle_b2(struct kvm_vcpu *vcpu);
 
 /* implemented in sigp.c */
 int kvm_s390_handle_sigp(struct kvm_vcpu *vcpu);
Index: kvm/arch/s390/kvm/priv.c
===================================================================
--- kvm.orig/arch/s390/kvm/priv.c
+++ kvm/arch/s390/kvm/priv.c
@@ -304,12 +304,24 @@ static intercept_handler_t priv_handlers
 	[0xb1] = handle_stfl,
 };
 
-int kvm_s390_handle_priv(struct kvm_vcpu *vcpu)
+int kvm_s390_handle_b2(struct kvm_vcpu *vcpu)
 {
 	intercept_handler_t handler;
 
+	/*
+	 * a lot of B2 instructions are priviledged. We first check for
+	 * the priviledges ones, that we can handle in the kernel. If the
+	 * kernel can handle this instruction, we check for the problem
+	 * state bit and (a) handle the instruction or (b) send a code 2
+	 * program check.
+	 * Anything else goes to userspace.*/
 	handler = priv_handlers[vcpu->arch.sie_block->ipa & 0x00ff];
-	if (handler)
-		return handler(vcpu);
+	if (handler) {
+		if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE)
+			return kvm_s390_inject_program_int(vcpu,
+						   PGM_PRIVILEGED_OPERATION);
+		else
+			return handler(vcpu);
+	}
 	return -ENOTSUPP;
 }