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

Christian Borntraeger
2009-01-22T09:28:33Z

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;
}