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, 360 insertions, 0 deletions

diff --git a/arch/arm/kvm/coproc.c b/arch/arm/kvm/coproc.c
index 0c433558591c..722efe3b1675 100644
--- a/arch/arm/kvm/coproc.c
+++ b/arch/arm/kvm/coproc.c
@@ -16,8 +16,368 @@
  * along with this program; if not, write to the Free Software
  * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  */
+#include <linux/mm.h>
 #include <linux/kvm_host.h>
+#include <asm/kvm_arm.h>
+#include <asm/kvm_host.h>
+#include <asm/kvm_emulate.h>
+#include <asm/kvm_coproc.h>
+#include <asm/cacheflush.h>
+#include <asm/cputype.h>
+#include <trace/events/kvm.h>
 
+#include "trace.h"
+#include "coproc.h"
+
+
+/******************************************************************************
+ * Co-processor emulation
+ *****************************************************************************/
+
+int kvm_handle_cp10_id(struct kvm_vcpu *vcpu, struct kvm_run *run)
+{
+	kvm_inject_undefined(vcpu);
+	return 1;
+}
+
+int kvm_handle_cp_0_13_access(struct kvm_vcpu *vcpu, struct kvm_run *run)
+{
+	/*
+	 * We can get here, if the host has been built without VFPv3 support,
+	 * but the guest attempted a floating point operation.
+	 */
+	kvm_inject_undefined(vcpu);
+	return 1;
+}
+
+int kvm_handle_cp14_load_store(struct kvm_vcpu *vcpu, struct kvm_run *run)
+{
+	kvm_inject_undefined(vcpu);
+	return 1;
+}
+
+int kvm_handle_cp14_access(struct kvm_vcpu *vcpu, struct kvm_run *run)
+{
+	kvm_inject_undefined(vcpu);
+	return 1;
+}
+
+/* See note at ARM ARM B1.14.4 */
+static bool access_dcsw(struct kvm_vcpu *vcpu,
+			const struct coproc_params *p,
+			const struct coproc_reg *r)
+{
+	u32 val;
+	int cpu;
+
+	cpu = get_cpu();
+
+	if (!p->is_write)
+		return read_from_write_only(vcpu, p);
+
+	cpumask_setall(&vcpu->arch.require_dcache_flush);
+	cpumask_clear_cpu(cpu, &vcpu->arch.require_dcache_flush);
+
+	/* If we were already preempted, take the long way around */
+	if (cpu != vcpu->arch.last_pcpu) {
+		flush_cache_all();
+		goto done;
+	}
+
+	val = *vcpu_reg(vcpu, p->Rt1);
+
+	switch (p->CRm) {
+	case 6:			/* Upgrade DCISW to DCCISW, as per HCR.SWIO */
+	case 14:		/* DCCISW */
+		asm volatile("mcr p15, 0, %0, c7, c14, 2" : : "r" (val));
+		break;
+
+	case 10:		/* DCCSW */
+		asm volatile("mcr p15, 0, %0, c7, c10, 2" : : "r" (val));
+		break;
+	}
+
+done:
+	put_cpu();
+
+	return true;
+}
+
+/*
+ * We could trap ID_DFR0 and tell the guest we don't support performance
+ * monitoring.  Unfortunately the patch to make the kernel check ID_DFR0 was
+ * NAKed, so it will read the PMCR anyway.
+ *
+ * Therefore we tell the guest we have 0 counters.  Unfortunately, we
+ * must always support PMCCNTR (the cycle counter): we just RAZ/WI for
+ * all PM registers, which doesn't crash the guest kernel at least.
+ */
+static bool pm_fake(struct kvm_vcpu *vcpu,
+		    const struct coproc_params *p,
+		    const struct coproc_reg *r)
+{
+	if (p->is_write)
+		return ignore_write(vcpu, p);
+	else
+		return read_zero(vcpu, p);
+}
+
+#define access_pmcr pm_fake
+#define access_pmcntenset pm_fake
+#define access_pmcntenclr pm_fake
+#define access_pmovsr pm_fake
+#define access_pmselr pm_fake
+#define access_pmceid0 pm_fake
+#define access_pmceid1 pm_fake
+#define access_pmccntr pm_fake
+#define access_pmxevtyper pm_fake
+#define access_pmxevcntr pm_fake
+#define access_pmuserenr pm_fake
+#define access_pmintenset pm_fake
+#define access_pmintenclr pm_fake
+
+/* Architected CP15 registers.
+ * Important: Must be sorted ascending by CRn, CRM, Op1, Op2
+ */
+static const struct coproc_reg cp15_regs[] = {
+	/* CSSELR: swapped by interrupt.S. */
+	{ CRn( 0), CRm( 0), Op1( 2), Op2( 0), is32,
+			NULL, reset_unknown, c0_CSSELR },
+
+	/* TTBR0/TTBR1: swapped by interrupt.S. */
+	{ CRm( 2), Op1( 0), is64, NULL, reset_unknown64, c2_TTBR0 },
+	{ CRm( 2), Op1( 1), is64, NULL, reset_unknown64, c2_TTBR1 },
+
+	/* TTBCR: swapped by interrupt.S. */
+	{ CRn( 2), CRm( 0), Op1( 0), Op2( 2), is32,
+			NULL, reset_val, c2_TTBCR, 0x00000000 },
+
+	/* DACR: swapped by interrupt.S. */
+	{ CRn( 3), CRm( 0), Op1( 0), Op2( 0), is32,
+			NULL, reset_unknown, c3_DACR },
+
+	/* DFSR/IFSR/ADFSR/AIFSR: swapped by interrupt.S. */
+	{ CRn( 5), CRm( 0), Op1( 0), Op2( 0), is32,
+			NULL, reset_unknown, c5_DFSR },
+	{ CRn( 5), CRm( 0), Op1( 0), Op2( 1), is32,
+			NULL, reset_unknown, c5_IFSR },
+	{ CRn( 5), CRm( 1), Op1( 0), Op2( 0), is32,
+			NULL, reset_unknown, c5_ADFSR },
+	{ CRn( 5), CRm( 1), Op1( 0), Op2( 1), is32,
+			NULL, reset_unknown, c5_AIFSR },
+
+	/* DFAR/IFAR: swapped by interrupt.S. */
+	{ CRn( 6), CRm( 0), Op1( 0), Op2( 0), is32,
+			NULL, reset_unknown, c6_DFAR },
+	{ CRn( 6), CRm( 0), Op1( 0), Op2( 2), is32,
+			NULL, reset_unknown, c6_IFAR },
+	/*
+	 * DC{C,I,CI}SW operations:
+	 */
+	{ CRn( 7), CRm( 6), Op1( 0), Op2( 2), is32, access_dcsw},
+	{ CRn( 7), CRm(10), Op1( 0), Op2( 2), is32, access_dcsw},
+	{ CRn( 7), CRm(14), Op1( 0), Op2( 2), is32, access_dcsw},
+	/*
+	 * Dummy performance monitor implementation.
+	 */
+	{ CRn( 9), CRm(12), Op1( 0), Op2( 0), is32, access_pmcr},
+	{ CRn( 9), CRm(12), Op1( 0), Op2( 1), is32, access_pmcntenset},
+	{ CRn( 9), CRm(12), Op1( 0), Op2( 2), is32, access_pmcntenclr},
+	{ CRn( 9), CRm(12), Op1( 0), Op2( 3), is32, access_pmovsr},
+	{ CRn( 9), CRm(12), Op1( 0), Op2( 5), is32, access_pmselr},
+	{ CRn( 9), CRm(12), Op1( 0), Op2( 6), is32, access_pmceid0},
+	{ CRn( 9), CRm(12), Op1( 0), Op2( 7), is32, access_pmceid1},
+	{ CRn( 9), CRm(13), Op1( 0), Op2( 0), is32, access_pmccntr},
+	{ CRn( 9), CRm(13), Op1( 0), Op2( 1), is32, access_pmxevtyper},
+	{ CRn( 9), CRm(13), Op1( 0), Op2( 2), is32, access_pmxevcntr},
+	{ CRn( 9), CRm(14), Op1( 0), Op2( 0), is32, access_pmuserenr},
+	{ CRn( 9), CRm(14), Op1( 0), Op2( 1), is32, access_pmintenset},
+	{ CRn( 9), CRm(14), Op1( 0), Op2( 2), is32, access_pmintenclr},
+
+	/* PRRR/NMRR (aka MAIR0/MAIR1): swapped by interrupt.S. */
+	{ CRn(10), CRm( 2), Op1( 0), Op2( 0), is32,
+			NULL, reset_unknown, c10_PRRR},
+	{ CRn(10), CRm( 2), Op1( 0), Op2( 1), is32,
+			NULL, reset_unknown, c10_NMRR},
+
+	/* VBAR: swapped by interrupt.S. */
+	{ CRn(12), CRm( 0), Op1( 0), Op2( 0), is32,
+			NULL, reset_val, c12_VBAR, 0x00000000 },
+
+	/* CONTEXTIDR/TPIDRURW/TPIDRURO/TPIDRPRW: swapped by interrupt.S. */
+	{ CRn(13), CRm( 0), Op1( 0), Op2( 1), is32,
+			NULL, reset_val, c13_CID, 0x00000000 },
+	{ CRn(13), CRm( 0), Op1( 0), Op2( 2), is32,
+			NULL, reset_unknown, c13_TID_URW },
+	{ CRn(13), CRm( 0), Op1( 0), Op2( 3), is32,
+			NULL, reset_unknown, c13_TID_URO },
+	{ CRn(13), CRm( 0), Op1( 0), Op2( 4), is32,
+			NULL, reset_unknown, c13_TID_PRIV },
+};
+
+/* Target specific emulation tables */
+static struct kvm_coproc_target_table *target_tables[KVM_ARM_NUM_TARGETS];
+
+void kvm_register_target_coproc_table(struct kvm_coproc_target_table *table)
+{
+	target_tables[table->target] = table;
+}
+
+/* Get specific register table for this target. */
+static const struct coproc_reg *get_target_table(unsigned target, size_t *num)
+{
+	struct kvm_coproc_target_table *table;
+
+	table = target_tables[target];
+	*num = table->num;
+	return table->table;
+}
+
+static const struct coproc_reg *find_reg(const struct coproc_params *params,
+					 const struct coproc_reg table[],
+					 unsigned int num)
+{
+	unsigned int i;
+
+	for (i = 0; i < num; i++) {
+		const struct coproc_reg *r = &table[i];
+
+		if (params->is_64bit != r->is_64)
+			continue;
+		if (params->CRn != r->CRn)
+			continue;
+		if (params->CRm != r->CRm)
+			continue;
+		if (params->Op1 != r->Op1)
+			continue;
+		if (params->Op2 != r->Op2)
+			continue;
+
+		return r;
+	}
+	return NULL;
+}
+
+static int emulate_cp15(struct kvm_vcpu *vcpu,
+			const struct coproc_params *params)
+{
+	size_t num;
+	const struct coproc_reg *table, *r;
+
+	trace_kvm_emulate_cp15_imp(params->Op1, params->Rt1, params->CRn,
+				   params->CRm, params->Op2, params->is_write);
+
+	table = get_target_table(vcpu->arch.target, &num);
+
+	/* Search target-specific then generic table. */
+	r = find_reg(params, table, num);
+	if (!r)
+		r = find_reg(params, cp15_regs, ARRAY_SIZE(cp15_regs));
+
+	if (likely(r)) {
+		/* If we don't have an accessor, we should never get here! */
+		BUG_ON(!r->access);
+
+		if (likely(r->access(vcpu, params, r))) {
+			/* Skip instruction, since it was emulated */
+			kvm_skip_instr(vcpu, (vcpu->arch.hsr >> 25) & 1);
+			return 1;
+		}
+		/* If access function fails, it should complain. */
+	} else {
+		kvm_err("Unsupported guest CP15 access at: %08x\n",
+			*vcpu_pc(vcpu));
+		print_cp_instr(params);
+	}
+	kvm_inject_undefined(vcpu);
+	return 1;
+}
+
+/**
+ * kvm_handle_cp15_64 -- handles a mrrc/mcrr trap on a guest CP15 access
+ * @vcpu: The VCPU pointer
+ * @run:  The kvm_run struct
+ */
+int kvm_handle_cp15_64(struct kvm_vcpu *vcpu, struct kvm_run *run)
+{
+	struct coproc_params params;
+
+	params.CRm = (vcpu->arch.hsr >> 1) & 0xf;
+	params.Rt1 = (vcpu->arch.hsr >> 5) & 0xf;
+	params.is_write = ((vcpu->arch.hsr & 1) == 0);
+	params.is_64bit = true;
+
+	params.Op1 = (vcpu->arch.hsr >> 16) & 0xf;
+	params.Op2 = 0;
+	params.Rt2 = (vcpu->arch.hsr >> 10) & 0xf;
+	params.CRn = 0;
+
+	return emulate_cp15(vcpu, &params);
+}
+
+static void reset_coproc_regs(struct kvm_vcpu *vcpu,
+			      const struct coproc_reg *table, size_t num)
+{
+	unsigned long i;
+
+	for (i = 0; i < num; i++)
+		if (table[i].reset)
+			table[i].reset(vcpu, &table[i]);
+}
+
+/**
+ * kvm_handle_cp15_32 -- handles a mrc/mcr trap on a guest CP15 access
+ * @vcpu: The VCPU pointer
+ * @run:  The kvm_run struct
+ */
+int kvm_handle_cp15_32(struct kvm_vcpu *vcpu, struct kvm_run *run)
+{
+	struct coproc_params params;
+
+	params.CRm = (vcpu->arch.hsr >> 1) & 0xf;
+	params.Rt1 = (vcpu->arch.hsr >> 5) & 0xf;
+	params.is_write = ((vcpu->arch.hsr & 1) == 0);
+	params.is_64bit = false;
+
+	params.CRn = (vcpu->arch.hsr >> 10) & 0xf;
+	params.Op1 = (vcpu->arch.hsr >> 14) & 0x7;
+	params.Op2 = (vcpu->arch.hsr >> 17) & 0x7;
+	params.Rt2 = 0;
+
+	return emulate_cp15(vcpu, &params);
+}
+
+void kvm_coproc_table_init(void)
+{
+	unsigned int i;
+
+	/* Make sure tables are unique and in order. */
+	for (i = 1; i < ARRAY_SIZE(cp15_regs); i++)
+		BUG_ON(cmp_reg(&cp15_regs[i-1], &cp15_regs[i]) >= 0);
+}
+
+/**
+ * kvm_reset_coprocs - sets cp15 registers to reset value
+ * @vcpu: The VCPU pointer
+ *
+ * This function finds the right table above and sets the registers on the
+ * virtual CPU struct to their architecturally defined reset values.
+ */
 void kvm_reset_coprocs(struct kvm_vcpu *vcpu)
 {
+	size_t num;
+	const struct coproc_reg *table;
+
+	/* Catch someone adding a register without putting in reset entry. */
+	memset(vcpu->arch.cp15, 0x42, sizeof(vcpu->arch.cp15));
+
+	/* Generic chip reset first (so target could override). */
+	reset_coproc_regs(vcpu, cp15_regs, ARRAY_SIZE(cp15_regs));
+
+	table = get_target_table(vcpu->arch.target, &num);
+	reset_coproc_regs(vcpu, table, num);
+
+	for (num = 1; num < NR_CP15_REGS; num++)
+		if (vcpu->arch.cp15[num] == 0x42424242)
+			panic("Didn't reset vcpu->arch.cp15[%zi]", num);
 }