static int emulate_store()

in kvm/vcpu_exit.c [300:418]

• 92 lines of code
• 20 McCabe index (conditional complexity)

static int emulate_store(struct kvm_vcpu *vcpu, struct kvm_run *run,
			 unsigned long fault_addr, unsigned long htinst)
{
	u8 data8;
	u16 data16;
	u32 data32;
	u64 data64;
	ulong data;
	unsigned long insn;
	int 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);
	}

	data = GET_RS2(insn, &vcpu->arch.guest_context);
	data8 = data16 = data32 = data64 = data;

	if ((insn & INSN_MASK_SW) == INSN_MATCH_SW) {
		len = 4;
	} else if ((insn & INSN_MASK_SB) == INSN_MATCH_SB) {
		len = 1;
#ifdef CONFIG_64BIT
	} else if ((insn & INSN_MASK_SD) == INSN_MATCH_SD) {
		len = 8;
#endif
	} else if ((insn & INSN_MASK_SH) == INSN_MATCH_SH) {
		len = 2;
#ifdef CONFIG_64BIT
	} else if ((insn & INSN_MASK_C_SD) == INSN_MATCH_C_SD) {
		len = 8;
		data64 = GET_RS2S(insn, &vcpu->arch.guest_context);
	} else if ((insn & INSN_MASK_C_SDSP) == INSN_MATCH_C_SDSP &&
		   ((insn >> SH_RD) & 0x1f)) {
		len = 8;
		data64 = GET_RS2C(insn, &vcpu->arch.guest_context);
#endif
	} else if ((insn & INSN_MASK_C_SW) == INSN_MATCH_C_SW) {
		len = 4;
		data32 = GET_RS2S(insn, &vcpu->arch.guest_context);
	} else if ((insn & INSN_MASK_C_SWSP) == INSN_MATCH_C_SWSP &&
		   ((insn >> SH_RD) & 0x1f)) {
		len = 4;
		data32 = GET_RS2C(insn, &vcpu->arch.guest_context);
	} 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 = 0;
	vcpu->arch.mmio_decode.len = len;
	vcpu->arch.mmio_decode.return_handled = 0;

	/* Copy data to kvm_run instance */
	switch (len) {
	case 1:
		*((u8 *)run->mmio.data) = data8;
		break;
	case 2:
		*((u16 *)run->mmio.data) = data16;
		break;
	case 4:
		*((u32 *)run->mmio.data) = data32;
		break;
	case 8:
		*((u64 *)run->mmio.data) = data64;
		break;
	default:
		return -EOPNOTSUPP;
	}

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

	/* Try to handle MMIO access in the kernel */
	if (!kvm_io_bus_write(vcpu, KVM_MMIO_BUS,
			      fault_addr, len, run->mmio.data)) {
		/* Successfully handled MMIO access in the kernel so resume */
		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;
}