[PATCH v3 2/9] s390: ap: kvm: setting a hook for PQAP instructions

[Pierre Morel]

This patch adds interception code for the PQAP instructions,
and a callback inside the KVM arch structure for s390.

If a VFIO-AP drivers needs to intercept PQAP/AQIC or PQAP/TAPQ
instructions, the driver will initialize the callback inside
the kvm_arch structure to be called when the interception of a
PQAP instruction occurs.

If the callback is not initialized, the code still returns
-EOPNOTSUPP to let userland handle the instruction as it used to.

Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
Reviewed-by: Tony Krowiak <akrowiak@xxxxxxxxxxxxx>
---
 arch/s390/include/asm/kvm_host.h |  1 +
 arch/s390/kvm/priv.c             | 50 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 51 insertions(+)

diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index c5f5156..49cc8b0 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -719,6 +719,7 @@ struct kvm_s390_cpu_model {
 
 struct kvm_s390_crypto {
 	struct kvm_s390_crypto_cb *crycb;
+	int (*pqap_hook)(struct kvm_vcpu *vcpu);
 	__u32 crycbd;
 	__u8 aes_kw;
 	__u8 dea_kw;
diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
index 8679bd7..72fdc21 100644
--- a/arch/s390/kvm/priv.c
+++ b/arch/s390/kvm/priv.c
@@ -27,6 +27,7 @@
 #include <asm/io.h>
 #include <asm/ptrace.h>
 #include <asm/sclp.h>
+#include <asm/ap.h>
 #include "gaccess.h"
 #include "kvm-s390.h"
 #include "trace.h"
@@ -592,6 +593,53 @@ static int handle_io_inst(struct kvm_vcpu *vcpu)
 	}
 }
 
+/*
+ * handle_pqap: Handling pqap interception
+ * @vcpu: the vcpu having issue the pqap instruction
+ *
+ * This callback only handles PQAP/AQIC instruction and
+ * calls a dedicated callback for this instruction if
+ * a driver did register one in the CRYPTO satellite of the
+ * SIE block.
+ *
+ * Do not change the behavior if, return -EOPNOTSUPP if:
+ * - the hook is not used do not change the behavior.
+ * - AP instructions are not available or not available to the guest
+ * - the instruction is not PQAP with function code indicating
+ *   AQIC do not change the previous behavior.
+ *
+ * For PQAP/AQIC instruction, verify privilege and specifications
+ *
+ * return the value returned by the callback.
+ */
+static int handle_pqap(struct kvm_vcpu *vcpu)
+{
+	uint8_t fc;
+
+	/* Verify that the hook callback is registered */
+	if (!vcpu->kvm->arch.crypto.pqap_hook)
+		return -EOPNOTSUPP;
+	/* Verify that the AP instruction are available */
+	if (!ap_instructions_available())
+		return -EOPNOTSUPP;
+	/* Verify that the guest is allowed to use AP instructions */
+	if (!(vcpu->arch.sie_block->eca & ECA_APIE))
+		return -EOPNOTSUPP;
+	/* Verify that the function code is AQIC */
+	fc = vcpu->run->s.regs.gprs[0] >> 24;
+	if (fc != 0x03)
+		return -EOPNOTSUPP;
+
+	/* PQAP instructions are allowed for guest kernel only */
+	if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE)
+		return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP);
+	/* AQIC instruction is allowed only if facility 65 is available */
+	if (!test_kvm_facility(vcpu->kvm, 65))
+		return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
+	/* All right, call the callback */
+	return vcpu->kvm->arch.crypto.pqap_hook(vcpu);
+}
+
 static int handle_stfl(struct kvm_vcpu *vcpu)
 {
 	int rc;
@@ -878,6 +926,8 @@ int kvm_s390_handle_b2(struct kvm_vcpu *vcpu)
 		return handle_sthyi(vcpu);
 	case 0x7d:
 		return handle_stsi(vcpu);
+	case 0xaf:
+		return handle_pqap(vcpu);
 	case 0xb1:
 		return handle_stfl(vcpu);
 	case 0xb2:
-- 
2.7.4