trap_emul.c

/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * KVM/MIPS: Deliver/Emulate exceptions to the guest kernel
 *
 * Copyright (C) 2012  MIPS Technologies, Inc.  All rights reserved.
 * Authors: Sanjay Lal <sanjayl@kymasys.com>
 */

#include <linux/errno.h>
#include <linux/err.h>
#include <linux/kvm_host.h>
#include <linux/uaccess.h>
#include <linux/vmalloc.h>
#include <asm/mmu_context.h>
#include <asm/pgalloc.h>

#include "interrupt.h"

static gpa_t kvm_trap_emul_gva_to_gpa_cb(gva_t gva)
{
	gpa_t gpa;
	gva_t kseg = KSEGX(gva);

	if ((kseg == CKSEG0) || (kseg == CKSEG1))
		gpa = CPHYSADDR(gva);
	else {
		kvm_err("%s: cannot find GPA for GVA: %#lx\n", __func__, gva);
		kvm_mips_dump_host_tlbs();
		gpa = KVM_INVALID_ADDR;
	}

	kvm_debug("%s: gva %#lx, gpa: %#llx\n", __func__, gva, gpa);

	return gpa;
}

static int kvm_trap_emul_handle_cop_unusable(struct kvm_vcpu *vcpu)
{
	struct mips_coproc *cop0 = vcpu->arch.cop0;
	struct kvm_run *run = vcpu->run;
	u32 __user *opc = (u32 __user *) vcpu->arch.pc;
	u32 cause = vcpu->arch.host_cp0_cause;
	enum emulation_result er = EMULATE_DONE;
	int ret = RESUME_GUEST;

	if (((cause & CAUSEF_CE) >> CAUSEB_CE) == 1) {
		/* FPU Unusable */
		if (!kvm_mips_guest_has_fpu(&vcpu->arch) ||
		    (kvm_read_c0_guest_status(cop0) & ST0_CU1) == 0) {
			/*
			 * Unusable/no FPU in guest:
			 * deliver guest COP1 Unusable Exception
			 */
			er = kvm_mips_emulate_fpu_exc(cause, opc, run, vcpu);
		} else {
			/* Restore FPU state */
			kvm_own_fpu(vcpu);
			er = EMULATE_DONE;
		}
	} else {
		er = kvm_mips_emulate_inst(cause, opc, run, vcpu);
	}

	switch (er) {
	case EMULATE_DONE:
		ret = RESUME_GUEST;
		break;

	case EMULATE_FAIL:
		run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
		ret = RESUME_HOST;
		break;

	case EMULATE_WAIT:
		run->exit_reason = KVM_EXIT_INTR;
		ret = RESUME_HOST;
		break;

	default:
		BUG();
	}
	return ret;
}

static int kvm_trap_emul_handle_tlb_mod(struct kvm_vcpu *vcpu)
{
	struct kvm_run *run = vcpu->run;
	u32 __user *opc = (u32 __user *) vcpu->arch.pc;
	unsigned long badvaddr = vcpu->arch.host_cp0_badvaddr;
	u32 cause = vcpu->arch.host_cp0_cause;
	enum emulation_result er = EMULATE_DONE;
	int ret = RESUME_GUEST;

	if (KVM_GUEST_KSEGX(badvaddr) < KVM_GUEST_KSEG0
	    || KVM_GUEST_KSEGX(badvaddr) == KVM_GUEST_KSEG23) {
		kvm_debug("USER/KSEG23 ADDR TLB MOD fault: cause %#x, PC: %p, BadVaddr: %#lx\n",
			  cause, opc, badvaddr);
		er = kvm_mips_handle_tlbmod(cause, opc, run, vcpu);

		if (er == EMULATE_DONE)
			ret = RESUME_GUEST;
		else {
			run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
			ret = RESUME_HOST;
		}
	} else if (KVM_GUEST_KSEGX(badvaddr) == KVM_GUEST_KSEG0) {
		/*
		 * XXXKYMA: The guest kernel does not expect to get this fault
		 * when we are not using HIGHMEM. Need to address this in a
		 * HIGHMEM kernel
		 */
		kvm_err("TLB MOD fault not handled, cause %#x, PC: %p, BadVaddr: %#lx\n",
			cause, opc, badvaddr);
		kvm_mips_dump_host_tlbs();
		kvm_arch_vcpu_dump_regs(vcpu);
		run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
		ret = RESUME_HOST;
	} else {
		kvm_err("Illegal TLB Mod fault address , cause %#x, PC: %p, BadVaddr: %#lx\n",
			cause, opc, badvaddr);
		kvm_mips_dump_host_tlbs();
		kvm_arch_vcpu_dump_regs(vcpu);
		run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
		ret = RESUME_HOST;
	}
	return ret;
}

static int kvm_trap_emul_handle_tlb_miss(struct kvm_vcpu *vcpu, bool store)
{
	struct kvm_run *run = vcpu->run;
	u32 __user *opc = (u32 __user *) vcpu->arch.pc;
	unsigned long badvaddr = vcpu->arch.host_cp0_badvaddr;
	u32 cause = vcpu->arch.host_cp0_cause;
	enum emulation_result er = EMULATE_DONE;
	int ret = RESUME_GUEST;

	if (((badvaddr & PAGE_MASK) == KVM_GUEST_COMMPAGE_ADDR)
	    && KVM_GUEST_KERNEL_MODE(vcpu)) {
		if (kvm_mips_handle_commpage_tlb_fault(badvaddr, vcpu) < 0) {
			run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
			ret = RESUME_HOST;
		}
	} else if (KVM_GUEST_KSEGX(badvaddr) < KVM_GUEST_KSEG0
		   || KVM_GUEST_KSEGX(badvaddr) == KVM_GUEST_KSEG23) {
		kvm_debug("USER ADDR TLB %s fault: cause %#x, PC: %p, BadVaddr: %#lx\n",
			  store ? "ST" : "LD", cause, opc, badvaddr);

		/*
		 * User Address (UA) fault, this could happen if
		 * (1) TLB entry not present/valid in both Guest and shadow host
		 *     TLBs, in this case we pass on the fault to the guest
		 *     kernel and let it handle it.
		 * (2) TLB entry is present in the Guest TLB but not in the
		 *     shadow, in this case we inject the TLB from the Guest TLB
		 *     into the shadow host TLB
		 */

		er = kvm_mips_handle_tlbmiss(cause, opc, run, vcpu);
		if (er == EMULATE_DONE)
			ret = RESUME_GUEST;
		else {
			run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
			ret = RESUME_HOST;
		}
	} else if (KVM_GUEST_KSEGX(badvaddr) == KVM_GUEST_KSEG0) {
		/*
		 * All KSEG0 faults are handled by KVM, as the guest kernel does
		 * not expect to ever get them
		 */
		if (kvm_mips_handle_kseg0_tlb_fault
		    (vcpu->arch.host_cp0_badvaddr, vcpu) < 0) {
			run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
			ret = RESUME_HOST;
		}
	} else if (KVM_GUEST_KERNEL_MODE(vcpu)
		   && (KSEGX(badvaddr) == CKSEG0 || KSEGX(badvaddr) == CKSEG1)) {
		/* A code fetch fault doesn't count as an MMIO */
		if (!store && kvm_is_ifetch_fault(&vcpu->arch)) {
			run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
			return RESUME_HOST;
		}

		/*
		 * With EVA we may get a TLB exception instead of an address
		 * error when the guest performs MMIO to KSeg1 addresses.
		 */
		kvm_debug("Emulate %s MMIO space\n",
			  store ? "Store to" : "Load from");
		er = kvm_mips_emulate_inst(cause, opc, run, vcpu);
		if (er == EMULATE_FAIL) {
			kvm_err("Emulate %s MMIO space failed\n",
				store ? "Store to" : "Load from");
			run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
			ret = RESUME_HOST;
		} else {
			run->exit_reason = KVM_EXIT_MMIO;
			ret = RESUME_HOST;
		}
	} else {
		kvm_err("Illegal TLB %s fault address , cause %#x, PC: %p, BadVaddr: %#lx\n",
			store ? "ST" : "LD", cause, opc, badvaddr);
		kvm_mips_dump_host_tlbs();
		kvm_arch_vcpu_dump_regs(vcpu);
		run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
		ret = RESUME_HOST;
	}
	return ret;
}

static int kvm_trap_emul_handle_tlb_st_miss(struct kvm_vcpu *vcpu)
{
	return kvm_trap_emul_handle_tlb_miss(vcpu, true);
}

static int kvm_trap_emul_handle_tlb_ld_miss(struct kvm_vcpu *vcpu)
{
	return kvm_trap_emul_handle_tlb_miss(vcpu, false);
}

static int kvm_trap_emul_handle_addr_err_st(struct kvm_vcpu *vcpu)
{
	struct kvm_run *run = vcpu->run;
	u32 __user *opc = (u32 __user *) vcpu->arch.pc;
	unsigned long badvaddr = vcpu->arch.host_cp0_badvaddr;
	u32 cause = vcpu->arch.host_cp0_cause;
	enum emulation_result er = EMULATE_DONE;
	int ret = RESUME_GUEST;

	if (KVM_GUEST_KERNEL_MODE(vcpu)
	    && (KSEGX(badvaddr) == CKSEG0 || KSEGX(badvaddr) == CKSEG1)) {
		kvm_debug("Emulate Store to MMIO space\n");
		er = kvm_mips_emulate_inst(cause, opc, run, vcpu);
		if (er == EMULATE_FAIL) {
			kvm_err("Emulate Store to MMIO space failed\n");
			run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
			ret = RESUME_HOST;
		} else {
			run->exit_reason = KVM_EXIT_MMIO;
			ret = RESUME_HOST;
		}
	} else {
		kvm_err("Address Error (STORE): cause %#x, PC: %p, BadVaddr: %#lx\n",
			cause, opc, badvaddr);
		run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
		ret = RESUME_HOST;
	}
	return ret;
}

static int kvm_trap_emul_handle_addr_err_ld(struct kvm_vcpu *vcpu)
{
	struct kvm_run *run = vcpu->run;
	u32 __user *opc = (u32 __user *) vcpu->arch.pc;
	unsigned long badvaddr = vcpu->arch.host_cp0_badvaddr;
	u32 cause = vcpu->arch.host_cp0_cause;
	enum emulation_result er = EMULATE_DONE;
	int ret = RESUME_GUEST;

	if (KSEGX(badvaddr) == CKSEG0 || KSEGX(badvaddr) == CKSEG1) {
		/* A code fetch fault doesn't count as an MMIO */
		if (kvm_is_ifetch_fault(&vcpu->arch)) {
			run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
			return RESUME_HOST;
		}

		kvm_debug("Emulate Load from MMIO space @ %#lx\n", badvaddr);
		er = kvm_mips_emulate_inst(cause, opc, run, vcpu);
		if (er == EMULATE_FAIL) {
			kvm_err("Emulate Load from MMIO space failed\n");
			run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
			ret = RESUME_HOST;
		} else {
			run->exit_reason = KVM_EXIT_MMIO;
			ret = RESUME_HOST;
		}
	} else {
		kvm_err("Address Error (LOAD): cause %#x, PC: %p, BadVaddr: %#lx\n",
			cause, opc, badvaddr);
		run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
		ret = RESUME_HOST;
		er = EMULATE_FAIL;
	}
	return ret;
}

static int kvm_trap_emul_handle_syscall(struct kvm_vcpu *vcpu)
{
	struct kvm_run *run = vcpu->run;
	u32 __user *opc = (u32 __user *) vcpu->arch.pc;
	u32 cause = vcpu->arch.host_cp0_cause;
	enum emulation_result er = EMULATE_DONE;
	int ret = RESUME_GUEST;

	er = kvm_mips_emulate_syscall(cause, opc, run, vcpu);
	if (er == EMULATE_DONE)
		ret = RESUME_GUEST;
	else {
		run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
		ret = RESUME_HOST;
	}
	return ret;
}

static int kvm_trap_emul_handle_res_inst(struct kvm_vcpu *vcpu)
{
	struct kvm_run *run = vcpu->run;
	u32 __user *opc = (u32 __user *) vcpu->arch.pc;
	u32 cause = vcpu->arch.host_cp0_cause;
	enum emulation_result er = EMULATE_DONE;
	int ret = RESUME_GUEST;

	er = kvm_mips_handle_ri(cause, opc, run, vcpu);
	if (er == EMULATE_DONE)
		ret = RESUME_GUEST;
	else {
		run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
		ret = RESUME_HOST;
	}
	return ret;
}

static int kvm_trap_emul_handle_break(struct kvm_vcpu *vcpu)
{
	struct kvm_run *run = vcpu->run;
	u32 __user *opc = (u32 __user *) vcpu->arch.pc;
	u32 cause = vcpu->arch.host_cp0_cause;
	enum emulation_result er = EMULATE_DONE;
	int ret = RESUME_GUEST;

	er = kvm_mips_emulate_bp_exc(cause, opc, run, vcpu);
	if (er == EMULATE_DONE)
		ret = RESUME_GUEST;
	else {
		run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
		ret = RESUME_HOST;
	}
	return ret;
}

static int kvm_trap_emul_handle_trap(struct kvm_vcpu *vcpu)
{
	struct kvm_run *run = vcpu->run;
	u32 __user *opc = (u32 __user *)vcpu->arch.pc;
	u32 cause = vcpu->arch.host_cp0_cause;
	enum emulation_result er = EMULATE_DONE;
	int ret = RESUME_GUEST;

	er = kvm_mips_emulate_trap_exc(cause, opc, run, vcpu);
	if (er == EMULATE_DONE) {
		ret = RESUME_GUEST;
	} else {
		run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
		ret = RESUME_HOST;
	}
	return ret;
}

static int kvm_trap_emul_handle_msa_fpe(struct kvm_vcpu *vcpu)
{
	struct kvm_run *run = vcpu->run;
	u32 __user *opc = (u32 __user *)vcpu->arch.pc;
	u32 cause = vcpu->arch.host_cp0_cause;
	enum emulation_result er = EMULATE_DONE;
	int ret = RESUME_GUEST;

	er = kvm_mips_emulate_msafpe_exc(cause, opc, run, vcpu);
	if (er == EMULATE_DONE) {
		ret = RESUME_GUEST;
	} else {
		run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
		ret = RESUME_HOST;
	}
	return ret;
}

static int kvm_trap_emul_handle_fpe(struct kvm_vcpu *vcpu)
{
	struct kvm_run *run = vcpu->run;
	u32 __user *opc = (u32 __user *)vcpu->arch.pc;
	u32 cause = vcpu->arch.host_cp0_cause;
	enum emulation_result er = EMULATE_DONE;
	int ret = RESUME_GUEST;

	er = kvm_mips_emulate_fpe_exc(cause, opc, run, vcpu);
	if (er == EMULATE_DONE) {
		ret = RESUME_GUEST;
	} else {
		run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
		ret = RESUME_HOST;
	}
	return ret;
}

/**
 * kvm_trap_emul_handle_msa_disabled() - Guest used MSA while disabled in root.
 * @vcpu:	Virtual CPU context.
 *
 * Handle when the guest attempts to use MSA when it is disabled.
 */
static int kvm_trap_emul_handle_msa_disabled(struct kvm_vcpu *vcpu)
{
	struct mips_coproc *cop0 = vcpu->arch.cop0;
	struct kvm_run *run = vcpu->run;
	u32 __user *opc = (u32 __user *) vcpu->arch.pc;
	u32 cause = vcpu->arch.host_cp0_cause;
	enum emulation_result er = EMULATE_DONE;
	int ret = RESUME_GUEST;

	if (!kvm_mips_guest_has_msa(&vcpu->arch) ||
	    (kvm_read_c0_guest_status(cop0) & (ST0_CU1 | ST0_FR)) == ST0_CU1) {
		/*
		 * No MSA in guest, or FPU enabled and not in FR=1 mode,
		 * guest reserved instruction exception
		 */
		er = kvm_mips_emulate_ri_exc(cause, opc, run, vcpu);
	} else if (!(kvm_read_c0_guest_config5(cop0) & MIPS_CONF5_MSAEN)) {
		/* MSA disabled by guest, guest MSA disabled exception */
		er = kvm_mips_emulate_msadis_exc(cause, opc, run, vcpu);
	} else {
		/* Restore MSA/FPU state */
		kvm_own_msa(vcpu);
		er = EMULATE_DONE;
	}

	switch (er) {
	case EMULATE_DONE:
		ret = RESUME_GUEST;
		break;

	case EMULATE_FAIL:
		run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
		ret = RESUME_HOST;
		break;

	default:
		BUG();
	}
	return ret;
}

static int kvm_trap_emul_vcpu_init(struct kvm_vcpu *vcpu)
{
	struct mm_struct *kern_mm = &vcpu->arch.guest_kernel_mm;
	struct mm_struct *user_mm = &vcpu->arch.guest_user_mm;

	vcpu->arch.kscratch_enabled = 0xfc;

	/*
	 * Allocate GVA -> HPA page tables.
	 * MIPS doesn't use the mm_struct pointer argument.
	 */
	kern_mm->pgd = pgd_alloc(kern_mm);
	if (!kern_mm->pgd)
		return -ENOMEM;

	user_mm->pgd = pgd_alloc(user_mm);
	if (!user_mm->pgd) {
		pgd_free(kern_mm, kern_mm->pgd);
		return -ENOMEM;
	}

	return 0;
}

static void kvm_mips_emul_free_gva_pt(pgd_t *pgd)
{
	/* Don't free host kernel page tables copied from init_mm.pgd */
	const unsigned long end = 0x80000000;
	unsigned long pgd_va, pud_va, pmd_va;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;
	int i, j, k;

	for (i = 0; i < USER_PTRS_PER_PGD; i++) {
		if (pgd_none(pgd[i]))
			continue;

		pgd_va = (unsigned long)i << PGDIR_SHIFT;
		if (pgd_va >= end)
			break;
		pud = pud_offset(pgd + i, 0);
		for (j = 0; j < PTRS_PER_PUD; j++) {
			if (pud_none(pud[j]))
				continue;

			pud_va = pgd_va | ((unsigned long)j << PUD_SHIFT);
			if (pud_va >= end)
				break;
			pmd = pmd_offset(pud + j, 0);
			for (k = 0; k < PTRS_PER_PMD; k++) {
				if (pmd_none(pmd[k]))
					continue;

				pmd_va = pud_va | (k << PMD_SHIFT);
				if (pmd_va >= end)
					break;
				pte = pte_offset(pmd + k, 0);
				pte_free_kernel(NULL, pte);
			}
			pmd_free(NULL, pmd);
		}
		pud_free(NULL, pud);
	}
	pgd_free(NULL, pgd);
}

static void kvm_trap_emul_vcpu_uninit(struct kvm_vcpu *vcpu)
{
	kvm_mips_emul_free_gva_pt(vcpu->arch.guest_kernel_mm.pgd);
	kvm_mips_emul_free_gva_pt(vcpu->arch.guest_user_mm.pgd);
}

static int kvm_trap_emul_vcpu_setup(struct kvm_vcpu *vcpu)
{
	struct mips_coproc *cop0 = vcpu->arch.cop0;
	u32 config, config1;
	int vcpu_id = vcpu->vcpu_id;

	/*
	 * Arch specific stuff, set up config registers properly so that the
	 * guest will come up as expected
	 */
#ifndef CONFIG_CPU_MIPSR6
	/* r2-r5, simulate a MIPS 24kc */
	kvm_write_c0_guest_prid(cop0, 0x00019300);
#else
	/* r6+, simulate a generic QEMU machine */
	kvm_write_c0_guest_prid(cop0, 0x00010000);
#endif
	/*
	 * Have config1, Cacheable, noncoherent, write-back, write allocate.
	 * Endianness, arch revision & virtually tagged icache should match
	 * host.
	 */
	config = read_c0_config() & MIPS_CONF_AR;
	config |= MIPS_CONF_M | CONF_CM_CACHABLE_NONCOHERENT | MIPS_CONF_MT_TLB;
#ifdef CONFIG_CPU_BIG_ENDIAN
	config |= CONF_BE;
#endif
	if (cpu_has_vtag_icache)
		config |= MIPS_CONF_VI;
	kvm_write_c0_guest_config(cop0, config);

	/* Read the cache characteristics from the host Config1 Register */
	config1 = (read_c0_config1() & ~0x7f);

	/* Set up MMU size */
	config1 &= ~(0x3f << 25);
	config1 |= ((KVM_MIPS_GUEST_TLB_SIZE - 1) << 25);

	/* We unset some bits that we aren't emulating */
	config1 &= ~(MIPS_CONF1_C2 | MIPS_CONF1_MD | MIPS_CONF1_PC |
		     MIPS_CONF1_WR | MIPS_CONF1_CA);
	kvm_write_c0_guest_config1(cop0, config1);

	/* Have config3, no tertiary/secondary caches implemented */
	kvm_write_c0_guest_config2(cop0, MIPS_CONF_M);
	/* MIPS_CONF_M | (read_c0_config2() & 0xfff) */

	/* Have config4, UserLocal */
	kvm_write_c0_guest_config3(cop0, MIPS_CONF_M | MIPS_CONF3_ULRI);

	/* Have config5 */
	kvm_write_c0_guest_config4(cop0, MIPS_CONF_M);

	/* No config6 */
	kvm_write_c0_guest_config5(cop0, 0);

	/* Set Wait IE/IXMT Ignore in Config7, IAR, AR */
	kvm_write_c0_guest_config7(cop0, (MIPS_CONF7_WII) | (1 << 10));

	/*
	 * Setup IntCtl defaults, compatibility mode for timer interrupts (HW5)
	 */
	kvm_write_c0_guest_intctl(cop0, 0xFC000000);

	/* Put in vcpu id as CPUNum into Ebase Reg to handle SMP Guests */
	kvm_write_c0_guest_ebase(cop0, KVM_GUEST_KSEG0 |
				       (vcpu_id & MIPS_EBASE_CPUNUM));

	return 0;
}

static unsigned long kvm_trap_emul_num_regs(struct kvm_vcpu *vcpu)
{
	return 0;
}

static int kvm_trap_emul_copy_reg_indices(struct kvm_vcpu *vcpu,
					  u64 __user *indices)
{
	return 0;
}

static int kvm_trap_emul_get_one_reg(struct kvm_vcpu *vcpu,
				     const struct kvm_one_reg *reg,
				     s64 *v)
{
	switch (reg->id) {
	case KVM_REG_MIPS_CP0_COUNT:
		*v = kvm_mips_read_count(vcpu);
		break;
	case KVM_REG_MIPS_COUNT_CTL:
		*v = vcpu->arch.count_ctl;
		break;
	case KVM_REG_MIPS_COUNT_RESUME:
		*v = ktime_to_ns(vcpu->arch.count_resume);
		break;
	case KVM_REG_MIPS_COUNT_HZ:
		*v = vcpu->arch.count_hz;
		break;
	default:
		return -EINVAL;
	}
	return 0;
}

static int kvm_trap_emul_set_one_reg(struct kvm_vcpu *vcpu,
				     const struct kvm_one_reg *reg,
				     s64 v)
{
	struct mips_coproc *cop0 = vcpu->arch.cop0;
	int ret = 0;
	unsigned int cur, change;

	switch (reg->id) {
	case KVM_REG_MIPS_CP0_COUNT:
		kvm_mips_write_count(vcpu, v);
		break;
	case KVM_REG_MIPS_CP0_COMPARE:
		kvm_mips_write_compare(vcpu, v, false);
		break;
	case KVM_REG_MIPS_CP0_CAUSE:
		/*
		 * If the timer is stopped or started (DC bit) it must look
		 * atomic with changes to the interrupt pending bits (TI, IRQ5).
		 * A timer interrupt should not happen in between.
		 */
		if ((kvm_read_c0_guest_cause(cop0) ^ v) & CAUSEF_DC) {
			if (v & CAUSEF_DC) {
				/* disable timer first */
				kvm_mips_count_disable_cause(vcpu);
				kvm_change_c0_guest_cause(cop0, ~CAUSEF_DC, v);
			} else {
				/* enable timer last */
				kvm_change_c0_guest_cause(cop0, ~CAUSEF_DC, v);
				kvm_mips_count_enable_cause(vcpu);
			}
		} else {
			kvm_write_c0_guest_cause(cop0, v);
		}
		break;
	case KVM_REG_MIPS_CP0_CONFIG:
		/* read-only for now */
		break;
	case KVM_REG_MIPS_CP0_CONFIG1:
		cur = kvm_read_c0_guest_config1(cop0);
		change = (cur ^ v) & kvm_mips_config1_wrmask(vcpu);
		if (change) {
			v = cur ^ change;
			kvm_write_c0_guest_config1(cop0, v);
		}
		break;
	case KVM_REG_MIPS_CP0_CONFIG2:
		/* read-only for now */
		break;
	case KVM_REG_MIPS_CP0_CONFIG3:
		cur = kvm_read_c0_guest_config3(cop0);
		change = (cur ^ v) & kvm_mips_config3_wrmask(vcpu);
		if (change) {
			v = cur ^ change;
			kvm_write_c0_guest_config3(cop0, v);
		}
		break;
	case KVM_REG_MIPS_CP0_CONFIG4:
		cur = kvm_read_c0_guest_config4(cop0);
		change = (cur ^ v) & kvm_mips_config4_wrmask(vcpu);
		if (change) {
			v = cur ^ change;
			kvm_write_c0_guest_config4(cop0, v);
		}
		break;
	case KVM_REG_MIPS_CP0_CONFIG5:
		cur = kvm_read_c0_guest_config5(cop0);
		change = (cur ^ v) & kvm_mips_config5_wrmask(vcpu);
		if (change) {
			v = cur ^ change;
			kvm_write_c0_guest_config5(cop0, v);
		}
		break;
	case KVM_REG_MIPS_COUNT_CTL:
		ret = kvm_mips_set_count_ctl(vcpu, v);
		break;
	case KVM_REG_MIPS_COUNT_RESUME:
		ret = kvm_mips_set_count_resume(vcpu, v);
		break;
	case KVM_REG_MIPS_COUNT_HZ:
		ret = kvm_mips_set_count_hz(vcpu, v);
		break;
	default:
		return -EINVAL;
	}
	return ret;
}

static int kvm_trap_emul_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
{
	struct mm_struct *kern_mm = &vcpu->arch.guest_kernel_mm;
	struct mm_struct *user_mm = &vcpu->arch.guest_user_mm;
	struct mm_struct *mm;

	/* Allocate new kernel and user ASIDs if needed */

	if ((cpu_context(cpu, kern_mm) ^ asid_cache(cpu)) &
						asid_version_mask(cpu)) {
		get_new_mmu_context(kern_mm, cpu);

		kvm_debug("[%d]: cpu_context: %#lx\n", cpu,
			  cpu_context(cpu, current->mm));
		kvm_debug("[%d]: Allocated new ASID for Guest Kernel: %#lx\n",
			  cpu, cpu_context(cpu, kern_mm));
	}

	if ((cpu_context(cpu, user_mm) ^ asid_cache(cpu)) &
						asid_version_mask(cpu)) {
		get_new_mmu_context(user_mm, cpu);

		kvm_debug("[%d]: cpu_context: %#lx\n", cpu,
			  cpu_context(cpu, current->mm));
		kvm_debug("[%d]: Allocated new ASID for Guest User: %#lx\n",
			  cpu, cpu_context(cpu, user_mm));
	}

	/*
	 * Were we in guest context? If so then the pre-empted ASID is
	 * no longer valid, we need to set it to what it should be based
	 * on the mode of the Guest (Kernel/User)
	 */
	if (current->flags & PF_VCPU) {
		mm = KVM_GUEST_KERNEL_MODE(vcpu) ? kern_mm : user_mm;
		write_c0_entryhi(cpu_asid(cpu, mm));
		TLBMISS_HANDLER_SETUP_PGD(mm->pgd);
		kvm_mips_suspend_mm(cpu);
		ehb();
	}

	return 0;
}

static int kvm_trap_emul_vcpu_put(struct kvm_vcpu *vcpu, int cpu)
{
	kvm_lose_fpu(vcpu);

	if (current->flags & PF_VCPU) {
		/* Restore normal Linux process memory map */
		if (((cpu_context(cpu, current->mm) ^ asid_cache(cpu)) &
		     asid_version_mask(cpu))) {
			kvm_debug("%s: Dropping MMU Context:  %#lx\n", __func__,
				  cpu_context(cpu, current->mm));
			get_new_mmu_context(current->mm, cpu);
		}
		write_c0_entryhi(cpu_asid(cpu, current->mm));
		TLBMISS_HANDLER_SETUP_PGD(current->mm->pgd);
		kvm_mips_resume_mm(cpu);
		ehb();
	}

	return 0;
}

static void kvm_trap_emul_vcpu_reenter(struct kvm_run *run,
				       struct kvm_vcpu *vcpu)
{
	struct mm_struct *user_mm = &vcpu->arch.guest_user_mm;
	struct mips_coproc *cop0 = vcpu->arch.cop0;
	int i, cpu = smp_processor_id();
	unsigned int gasid;

	/*
	 * Lazy host ASID regeneration / PT flush for guest user mode.
	 * If the guest ASID has changed since the last guest usermode
	 * execution, regenerate the host ASID so as to invalidate stale TLB
	 * entries and flush GVA PT entries too.
	 */
	if (!KVM_GUEST_KERNEL_MODE(vcpu)) {
		gasid = kvm_read_c0_guest_entryhi(cop0) & KVM_ENTRYHI_ASID;
		if (gasid != vcpu->arch.last_user_gasid) {
			kvm_mips_flush_gva_pt(user_mm->pgd, KMF_USER);
			get_new_mmu_context(user_mm, cpu);
			for_each_possible_cpu(i)
				if (i != cpu)
					cpu_context(i, user_mm) = 0;
			vcpu->arch.last_user_gasid = gasid;
		}
	}
}

static int kvm_trap_emul_vcpu_run(struct kvm_run *run, struct kvm_vcpu *vcpu)
{
	int cpu = smp_processor_id();
	int r;

	/* Check if we have any exceptions/interrupts pending */
	kvm_mips_deliver_interrupts(vcpu,
				    kvm_read_c0_guest_cause(vcpu->arch.cop0));

	kvm_trap_emul_vcpu_reenter(run, vcpu);

	/*
	 * We use user accessors to access guest memory, but we don't want to
	 * invoke Linux page faulting.
	 */
	pagefault_disable();

	/* Disable hardware page table walking while in guest */
	htw_stop();

	/*
	 * While in guest context we're in the guest's address space, not the
	 * host process address space, so we need to be careful not to confuse
	 * e.g. cache management IPIs.
	 */
	kvm_mips_suspend_mm(cpu);

	r = vcpu->arch.vcpu_run(run, vcpu);

	/* We may have migrated while handling guest exits */
	cpu = smp_processor_id();

	/* Restore normal Linux process memory map */
	if (((cpu_context(cpu, current->mm) ^ asid_cache(cpu)) &
	     asid_version_mask(cpu)))
		get_new_mmu_context(current->mm, cpu);
	write_c0_entryhi(cpu_asid(cpu, current->mm));
	TLBMISS_HANDLER_SETUP_PGD(current->mm->pgd);
	kvm_mips_resume_mm(cpu);

	htw_start();

	pagefault_enable();

	return r;
}

static struct kvm_mips_callbacks kvm_trap_emul_callbacks = {
	/* exit handlers */
	.handle_cop_unusable = kvm_trap_emul_handle_cop_unusable,
	.handle_tlb_mod = kvm_trap_emul_handle_tlb_mod,
	.handle_tlb_st_miss = kvm_trap_emul_handle_tlb_st_miss,
	.handle_tlb_ld_miss = kvm_trap_emul_handle_tlb_ld_miss,
	.handle_addr_err_st = kvm_trap_emul_handle_addr_err_st,
	.handle_addr_err_ld = kvm_trap_emul_handle_addr_err_ld,
	.handle_syscall = kvm_trap_emul_handle_syscall,
	.handle_res_inst = kvm_trap_emul_handle_res_inst,
	.handle_break = kvm_trap_emul_handle_break,
	.handle_trap = kvm_trap_emul_handle_trap,
	.handle_msa_fpe = kvm_trap_emul_handle_msa_fpe,
	.handle_fpe = kvm_trap_emul_handle_fpe,
	.handle_msa_disabled = kvm_trap_emul_handle_msa_disabled,

	.vcpu_init = kvm_trap_emul_vcpu_init,
	.vcpu_uninit = kvm_trap_emul_vcpu_uninit,
	.vcpu_setup = kvm_trap_emul_vcpu_setup,
	.gva_to_gpa = kvm_trap_emul_gva_to_gpa_cb,
	.queue_timer_int = kvm_mips_queue_timer_int_cb,
	.dequeue_timer_int = kvm_mips_dequeue_timer_int_cb,
	.queue_io_int = kvm_mips_queue_io_int_cb,
	.dequeue_io_int = kvm_mips_dequeue_io_int_cb,
	.irq_deliver = kvm_mips_irq_deliver_cb,
	.irq_clear = kvm_mips_irq_clear_cb,
	.num_regs = kvm_trap_emul_num_regs,
	.copy_reg_indices = kvm_trap_emul_copy_reg_indices,
	.get_one_reg = kvm_trap_emul_get_one_reg,
	.set_one_reg = kvm_trap_emul_set_one_reg,
	.vcpu_load = kvm_trap_emul_vcpu_load,
	.vcpu_put = kvm_trap_emul_vcpu_put,
	.vcpu_run = kvm_trap_emul_vcpu_run,
	.vcpu_reenter = kvm_trap_emul_vcpu_reenter,
};

int kvm_mips_emulation_init(struct kvm_mips_callbacks **install_callbacks)
{
	*install_callbacks = &kvm_trap_emul_callbacks;
	return 0;
}