KVM: s390: sie intercept handling

This path introduces handling of sie intercepts in three flavors: Intercepts
are either handled completely in-kernel by kvm_handle_sie_intercept(),
or passed to userspace with corresponding data in struct kvm_run in case
kvm_handle_sie_intercept() returns -ENOTSUPP.
In case of partial execution in kernel with the need of userspace support,
kvm_handle_sie_intercept() may choose to set up struct kvm_run and return
-EREMOTE.

The trivial intercept reasons are handled in this patch:
handle_noop() just does nothing for intercepts that don't require our support
  at all
handle_stop() is called when a cpu enters stopped state, and it drops out to
  userland after updating our vcpu state
handle_validity() faults in the cpu lowcore if needed, or passes the request
  to userland

Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 80 insertions, 0 deletions

diff --git a/arch/s390/kvm/intercept.c b/arch/s390/kvm/intercept.c
new file mode 100644
index 0000000..e757230
--- /dev/null
+++ b/arch/s390/kvm/intercept.c
@@ -0,0 +1,80 @@
+/*
+ * intercept.c - in-kernel handling for sie intercepts
+ *
+ * Copyright IBM Corp. 2008
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License (version 2 only)
+ * as published by the Free Software Foundation.
+ *
+ *    Author(s): Carsten Otte <cotte@de.ibm.com>
+ *               Christian Borntraeger <borntraeger@de.ibm.com>
+ */
+
+#include <linux/kvm_host.h>
+#include <linux/errno.h>
+#include <linux/pagemap.h>
+
+#include <asm/kvm_host.h>
+
+#include "kvm-s390.h"
+
+static int handle_noop(struct kvm_vcpu *vcpu)
+{
+	switch (vcpu->arch.sie_block->icptcode) {
+	case 0x10:
+		vcpu->stat.exit_external_request++;
+		break;
+	case 0x14:
+		vcpu->stat.exit_external_interrupt++;
+		break;
+	default:
+		break; /* nothing */
+	}
+	return 0;
+}
+
+static int handle_stop(struct kvm_vcpu *vcpu)
+{
+	vcpu->stat.exit_stop_request++;
+	VCPU_EVENT(vcpu, 3, "%s", "cpu stopped");
+	atomic_clear_mask(CPUSTAT_RUNNING, &vcpu->arch.sie_block->cpuflags);
+	return -ENOTSUPP;
+}
+
+static int handle_validity(struct kvm_vcpu *vcpu)
+{
+	int viwhy = vcpu->arch.sie_block->ipb >> 16;
+	vcpu->stat.exit_validity++;
+	if (viwhy == 0x37) {
+		fault_in_pages_writeable((char __user *)
+					 vcpu->kvm->arch.guest_origin +
+					 vcpu->arch.sie_block->prefix,
+					 PAGE_SIZE);
+		return 0;
+	}
+	VCPU_EVENT(vcpu, 2, "unhandled validity intercept code %d",
+		   viwhy);
+	return -ENOTSUPP;
+}
+
+static const intercept_handler_t intercept_funcs[0x48 >> 2] = {
+	[0x00 >> 2] = handle_noop,
+	[0x10 >> 2] = handle_noop,
+	[0x14 >> 2] = handle_noop,
+	[0x20 >> 2] = handle_validity,
+	[0x28 >> 2] = handle_stop,
+};
+
+int kvm_handle_sie_intercept(struct kvm_vcpu *vcpu)
+{
+	intercept_handler_t func;
+	u8 code = vcpu->arch.sie_block->icptcode;
+
+	if (code & 3 || code > 0x48)
+		return -ENOTSUPP;
+	func = intercept_funcs[code >> 2];
+	if (func)
+		return func(vcpu);
+	return -ENOTSUPP;
+}