KVM: PPC: Book3S: Add infrastructure to implement kernel-side RTAS calls

For pseries machine emulation, in order to move the interrupt
controller code to the kernel, we need to intercept some RTAS
calls in the kernel itself.  This adds an infrastructure to allow
in-kernel handlers to be registered for RTAS services by name.
A new ioctl, KVM_PPC_RTAS_DEFINE_TOKEN, then allows userspace to
associate token values with those service names.  Then, when the
guest requests an RTAS service with one of those token values, it
will be handled by the relevant in-kernel handler rather than being
passed up to userspace as at present.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
[agraf: fix warning]
Signed-off-by: Alexander Graf <agraf@suse.de>

1 files changed, 182 insertions, 0 deletions

diff --git a/arch/powerpc/kvm/book3s_rtas.c b/arch/powerpc/kvm/book3s_rtas.c
new file mode 100644
index 000000000000..6ad7050eb67d
--- /dev/null
+++ b/arch/powerpc/kvm/book3s_rtas.c
@@ -0,0 +1,182 @@
+/*
+ * Copyright 2012 Michael Ellerman, IBM Corporation.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License, version 2, as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/kvm_host.h>
+#include <linux/kvm.h>
+#include <linux/err.h>
+
+#include <asm/uaccess.h>
+#include <asm/kvm_book3s.h>
+#include <asm/kvm_ppc.h>
+#include <asm/hvcall.h>
+#include <asm/rtas.h>
+
+
+struct rtas_handler {
+	void (*handler)(struct kvm_vcpu *vcpu, struct rtas_args *args);
+	char *name;
+};
+
+static struct rtas_handler rtas_handlers[] = { };
+
+struct rtas_token_definition {
+	struct list_head list;
+	struct rtas_handler *handler;
+	u64 token;
+};
+
+static int rtas_name_matches(char *s1, char *s2)
+{
+	struct kvm_rtas_token_args args;
+	return !strncmp(s1, s2, sizeof(args.name));
+}
+
+static int rtas_token_undefine(struct kvm *kvm, char *name)
+{
+	struct rtas_token_definition *d, *tmp;
+
+	lockdep_assert_held(&kvm->lock);
+
+	list_for_each_entry_safe(d, tmp, &kvm->arch.rtas_tokens, list) {
+		if (rtas_name_matches(d->handler->name, name)) {
+			list_del(&d->list);
+			kfree(d);
+			return 0;
+		}
+	}
+
+	/* It's not an error to undefine an undefined token */
+	return 0;
+}
+
+static int rtas_token_define(struct kvm *kvm, char *name, u64 token)
+{
+	struct rtas_token_definition *d;
+	struct rtas_handler *h = NULL;
+	bool found;
+	int i;
+
+	lockdep_assert_held(&kvm->lock);
+
+	list_for_each_entry(d, &kvm->arch.rtas_tokens, list) {
+		if (d->token == token)
+			return -EEXIST;
+	}
+
+	found = false;
+	for (i = 0; i < ARRAY_SIZE(rtas_handlers); i++) {
+		h = &rtas_handlers[i];
+		if (rtas_name_matches(h->name, name)) {
+			found = true;
+			break;
+		}
+	}
+
+	if (!found)
+		return -ENOENT;
+
+	d = kzalloc(sizeof(*d), GFP_KERNEL);
+	if (!d)
+		return -ENOMEM;
+
+	d->handler = h;
+	d->token = token;
+
+	list_add_tail(&d->list, &kvm->arch.rtas_tokens);
+
+	return 0;
+}
+
+int kvm_vm_ioctl_rtas_define_token(struct kvm *kvm, void __user *argp)
+{
+	struct kvm_rtas_token_args args;
+	int rc;
+
+	if (copy_from_user(&args, argp, sizeof(args)))
+		return -EFAULT;
+
+	mutex_lock(&kvm->lock);
+
+	if (args.token)
+		rc = rtas_token_define(kvm, args.name, args.token);
+	else
+		rc = rtas_token_undefine(kvm, args.name);
+
+	mutex_unlock(&kvm->lock);
+
+	return rc;
+}
+
+int kvmppc_rtas_hcall(struct kvm_vcpu *vcpu)
+{
+	struct rtas_token_definition *d;
+	struct rtas_args args;
+	rtas_arg_t *orig_rets;
+	gpa_t args_phys;
+	int rc;
+
+	/* r4 contains the guest physical address of the RTAS args */
+	args_phys = kvmppc_get_gpr(vcpu, 4);
+
+	rc = kvm_read_guest(vcpu->kvm, args_phys, &args, sizeof(args));
+	if (rc)
+		goto fail;
+
+	/*
+	 * args->rets is a pointer into args->args. Now that we've
+	 * copied args we need to fix it up to point into our copy,
+	 * not the guest args. We also need to save the original
+	 * value so we can restore it on the way out.
+	 */
+	orig_rets = args.rets;
+	args.rets = &args.args[args.nargs];
+
+	mutex_lock(&vcpu->kvm->lock);
+
+	rc = -ENOENT;
+	list_for_each_entry(d, &vcpu->kvm->arch.rtas_tokens, list) {
+		if (d->token == args.token) {
+			d->handler->handler(vcpu, &args);
+			rc = 0;
+			break;
+		}
+	}
+
+	mutex_unlock(&vcpu->kvm->lock);
+
+	if (rc == 0) {
+		args.rets = orig_rets;
+		rc = kvm_write_guest(vcpu->kvm, args_phys, &args, sizeof(args));
+		if (rc)
+			goto fail;
+	}
+
+	return rc;
+
+fail:
+	/*
+	 * We only get here if the guest has called RTAS with a bogus
+	 * args pointer. That means we can't get to the args, and so we
+	 * can't fail the RTAS call. So fail right out to userspace,
+	 * which should kill the guest.
+	 */
+	return rc;
+}
+
+void kvmppc_rtas_tokens_free(struct kvm *kvm)
+{
+	struct rtas_token_definition *d, *tmp;
+
+	lockdep_assert_held(&kvm->lock);
+
+	list_for_each_entry_safe(d, tmp, &kvm->arch.rtas_tokens, list) {
+		list_del(&d->list);
+		kfree(d);
+	}
+}