static int emulate_load()

in kvm/vcpu_exit.c [191:298]

• 83 lines of code
• 19 McCabe index (conditional complexity)

static int emulate_load(struct kvm_vcpu *vcpu, struct kvm_run *run,
			unsigned long fault_addr, unsigned long htinst)
{
	u8 data_buf[8];
	unsigned long insn;
	int shift = 0, len = 0, insn_len = 0;
	struct kvm_cpu_trap utrap = { 0 };
	struct kvm_cpu_context *ct = &vcpu->arch.guest_context;

	/* Determine trapped instruction */
	if (htinst & 0x1) {
		/*
		 * Bit[0] == 1 implies trapped instruction value is
		 * transformed instruction or custom instruction.
		 */
		insn = htinst | INSN_16BIT_MASK;
		insn_len = (htinst & BIT(1)) ? INSN_LEN(insn) : 2;
	} else {
		/*
		 * Bit[0] == 0 implies trapped instruction value is
		 * zero or special value.
		 */
		insn = kvm_riscv_vcpu_unpriv_read(vcpu, true, ct->sepc,
						  &utrap);
		if (utrap.scause) {
			/* Redirect trap if we failed to read instruction */
			utrap.sepc = ct->sepc;
			kvm_riscv_vcpu_trap_redirect(vcpu, &utrap);
			return 1;
		}
		insn_len = INSN_LEN(insn);
	}

	/* Decode length of MMIO and shift */
	if ((insn & INSN_MASK_LW) == INSN_MATCH_LW) {
		len = 4;
		shift = 8 * (sizeof(ulong) - len);
	} else if ((insn & INSN_MASK_LB) == INSN_MATCH_LB) {
		len = 1;
		shift = 8 * (sizeof(ulong) - len);
	} else if ((insn & INSN_MASK_LBU) == INSN_MATCH_LBU) {
		len = 1;
		shift = 8 * (sizeof(ulong) - len);
#ifdef CONFIG_64BIT
	} else if ((insn & INSN_MASK_LD) == INSN_MATCH_LD) {
		len = 8;
		shift = 8 * (sizeof(ulong) - len);
	} else if ((insn & INSN_MASK_LWU) == INSN_MATCH_LWU) {
		len = 4;
#endif
	} else if ((insn & INSN_MASK_LH) == INSN_MATCH_LH) {
		len = 2;
		shift = 8 * (sizeof(ulong) - len);
	} else if ((insn & INSN_MASK_LHU) == INSN_MATCH_LHU) {
		len = 2;
#ifdef CONFIG_64BIT
	} else if ((insn & INSN_MASK_C_LD) == INSN_MATCH_C_LD) {
		len = 8;
		shift = 8 * (sizeof(ulong) - len);
		insn = RVC_RS2S(insn) << SH_RD;
	} else if ((insn & INSN_MASK_C_LDSP) == INSN_MATCH_C_LDSP &&
		   ((insn >> SH_RD) & 0x1f)) {
		len = 8;
		shift = 8 * (sizeof(ulong) - len);
#endif
	} else if ((insn & INSN_MASK_C_LW) == INSN_MATCH_C_LW) {
		len = 4;
		shift = 8 * (sizeof(ulong) - len);
		insn = RVC_RS2S(insn) << SH_RD;
	} else if ((insn & INSN_MASK_C_LWSP) == INSN_MATCH_C_LWSP &&
		   ((insn >> SH_RD) & 0x1f)) {
		len = 4;
		shift = 8 * (sizeof(ulong) - len);
	} else {
		return -EOPNOTSUPP;
	}

	/* Fault address should be aligned to length of MMIO */
	if (fault_addr & (len - 1))
		return -EIO;

	/* Save instruction decode info */
	vcpu->arch.mmio_decode.insn = insn;
	vcpu->arch.mmio_decode.insn_len = insn_len;
	vcpu->arch.mmio_decode.shift = shift;
	vcpu->arch.mmio_decode.len = len;
	vcpu->arch.mmio_decode.return_handled = 0;

	/* Update MMIO details in kvm_run struct */
	run->mmio.is_write = false;
	run->mmio.phys_addr = fault_addr;
	run->mmio.len = len;

	/* Try to handle MMIO access in the kernel */
	if (!kvm_io_bus_read(vcpu, KVM_MMIO_BUS, fault_addr, len, data_buf)) {
		/* Successfully handled MMIO access in the kernel so resume */
		memcpy(run->mmio.data, data_buf, len);
		vcpu->stat.mmio_exit_kernel++;
		kvm_riscv_vcpu_mmio_return(vcpu, run);
		return 1;
	}

	/* Exit to userspace for MMIO emulation */
	vcpu->stat.mmio_exit_user++;
	run->exit_reason = KVM_EXIT_MMIO;

	return 0;
}