KVM: ARM: Emulation framework and CP15 emulation

Adds a new important function in the main KVM/ARM code called
handle_exit() which is called from kvm_arch_vcpu_ioctl_run() on returns
from guest execution. This function examines the Hyp-Syndrome-Register
(HSR), which contains information telling KVM what caused the exit from
the guest.

Some of the reasons for an exit are CP15 accesses, which are
not allowed from the guest and this commit handles these exits by
emulating the intended operation in software and skipping the guest
instruction.

Minor notes about the coproc register reset:
1) We reserve a value of 0 as an invalid cp15 offset, to catch bugs in our
   table, at cost of 4 bytes per vcpu.

2) Added comments on the table indicating how we handle each register, for
   simplicity of understanding.

Reviewed-by: Will Deacon <will.deacon@arm.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Christoffer Dall <c.dall@virtualopensystems.com>

1 files changed, 153 insertions, 0 deletions

diff --git a/arch/arm/kvm/coproc.h b/arch/arm/kvm/coproc.h
new file mode 100644
index 000000000000..992adfafa2ff
--- /dev/null
+++ b/arch/arm/kvm/coproc.h
@@ -0,0 +1,153 @@
+/*
+ * Copyright (C) 2012 - Virtual Open Systems and Columbia University
+ * Authors: Christoffer Dall <c.dall@virtualopensystems.com>
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+
+#ifndef __ARM_KVM_COPROC_LOCAL_H__
+#define __ARM_KVM_COPROC_LOCAL_H__
+
+struct coproc_params {
+	unsigned long CRn;
+	unsigned long CRm;
+	unsigned long Op1;
+	unsigned long Op2;
+	unsigned long Rt1;
+	unsigned long Rt2;
+	bool is_64bit;
+	bool is_write;
+};
+
+struct coproc_reg {
+	/* MRC/MCR/MRRC/MCRR instruction which accesses it. */
+	unsigned long CRn;
+	unsigned long CRm;
+	unsigned long Op1;
+	unsigned long Op2;
+
+	bool is_64;
+
+	/* Trapped access from guest, if non-NULL. */
+	bool (*access)(struct kvm_vcpu *,
+		       const struct coproc_params *,
+		       const struct coproc_reg *);
+
+	/* Initialization for vcpu. */
+	void (*reset)(struct kvm_vcpu *, const struct coproc_reg *);
+
+	/* Index into vcpu->arch.cp15[], or 0 if we don't need to save it. */
+	unsigned long reg;
+
+	/* Value (usually reset value) */
+	u64 val;
+};
+
+static inline void print_cp_instr(const struct coproc_params *p)
+{
+	/* Look, we even formatted it for you to paste into the table! */
+	if (p->is_64bit) {
+		kvm_pr_unimpl(" { CRm(%2lu), Op1(%2lu), is64, func_%s },\n",
+			      p->CRm, p->Op1, p->is_write ? "write" : "read");
+	} else {
+		kvm_pr_unimpl(" { CRn(%2lu), CRm(%2lu), Op1(%2lu), Op2(%2lu), is32,"
+			      " func_%s },\n",
+			      p->CRn, p->CRm, p->Op1, p->Op2,
+			      p->is_write ? "write" : "read");
+	}
+}
+
+static inline bool ignore_write(struct kvm_vcpu *vcpu,
+				const struct coproc_params *p)
+{
+	return true;
+}
+
+static inline bool read_zero(struct kvm_vcpu *vcpu,
+			     const struct coproc_params *p)
+{
+	*vcpu_reg(vcpu, p->Rt1) = 0;
+	return true;
+}
+
+static inline bool write_to_read_only(struct kvm_vcpu *vcpu,
+				      const struct coproc_params *params)
+{
+	kvm_debug("CP15 write to read-only register at: %08x\n",
+		  *vcpu_pc(vcpu));
+	print_cp_instr(params);
+	return false;
+}
+
+static inline bool read_from_write_only(struct kvm_vcpu *vcpu,
+					const struct coproc_params *params)
+{
+	kvm_debug("CP15 read to write-only register at: %08x\n",
+		  *vcpu_pc(vcpu));
+	print_cp_instr(params);
+	return false;
+}
+
+/* Reset functions */
+static inline void reset_unknown(struct kvm_vcpu *vcpu,
+				 const struct coproc_reg *r)
+{
+	BUG_ON(!r->reg);
+	BUG_ON(r->reg >= ARRAY_SIZE(vcpu->arch.cp15));
+	vcpu->arch.cp15[r->reg] = 0xdecafbad;
+}
+
+static inline void reset_val(struct kvm_vcpu *vcpu, const struct coproc_reg *r)
+{
+	BUG_ON(!r->reg);
+	BUG_ON(r->reg >= ARRAY_SIZE(vcpu->arch.cp15));
+	vcpu->arch.cp15[r->reg] = r->val;
+}
+
+static inline void reset_unknown64(struct kvm_vcpu *vcpu,
+				   const struct coproc_reg *r)
+{
+	BUG_ON(!r->reg);
+	BUG_ON(r->reg + 1 >= ARRAY_SIZE(vcpu->arch.cp15));
+
+	vcpu->arch.cp15[r->reg] = 0xdecafbad;
+	vcpu->arch.cp15[r->reg+1] = 0xd0c0ffee;
+}
+
+static inline int cmp_reg(const struct coproc_reg *i1,
+			  const struct coproc_reg *i2)
+{
+	BUG_ON(i1 == i2);
+	if (!i1)
+		return 1;
+	else if (!i2)
+		return -1;
+	if (i1->CRn != i2->CRn)
+		return i1->CRn - i2->CRn;
+	if (i1->CRm != i2->CRm)
+		return i1->CRm - i2->CRm;
+	if (i1->Op1 != i2->Op1)
+		return i1->Op1 - i2->Op1;
+	return i1->Op2 - i2->Op2;
+}
+
+
+#define CRn(_x)		.CRn = _x
+#define CRm(_x) 	.CRm = _x
+#define Op1(_x) 	.Op1 = _x
+#define Op2(_x) 	.Op2 = _x
+#define is64		.is_64 = true
+#define is32		.is_64 = false
+
+#endif /* __ARM_KVM_COPROC_LOCAL_H__ */