mmio.c

/*
 * Copyright (C) 2012 - Virtual Open Systems and Columbia University
 * Author: 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.
 */

#include <linux/kvm_host.h>
#include <asm/kvm_mmio.h>
#include <asm/kvm_emulate.h>
#include <trace/events/kvm.h>

#include "trace.h"

/**
 * kvm_handle_mmio_return -- Handle MMIO loads after user space emulation
 * @vcpu: The VCPU pointer
 * @run:  The VCPU run struct containing the mmio data
 *
 * This should only be called after returning from userspace for MMIO load
 * emulation.
 */
int kvm_handle_mmio_return(struct kvm_vcpu *vcpu, struct kvm_run *run)
{
	unsigned long *dest;
	unsigned int len;
	int mask;

	if (!run->mmio.is_write) {
		dest = vcpu_reg(vcpu, vcpu->arch.mmio_decode.rt);
		memset(dest, 0, sizeof(int));

		len = run->mmio.len;
		if (len > 4)
			return -EINVAL;

		memcpy(dest, run->mmio.data, len);

		trace_kvm_mmio(KVM_TRACE_MMIO_READ, len, run->mmio.phys_addr,
				*((u64 *)run->mmio.data));

		if (vcpu->arch.mmio_decode.sign_extend && len < 4) {
			mask = 1U << ((len * 8) - 1);
			*dest = (*dest ^ mask) - mask;
		}
	}

	return 0;
}

static int decode_hsr(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
		      struct kvm_exit_mmio *mmio)
{
	unsigned long rt, len;
	bool is_write, sign_extend;

	if ((vcpu->arch.hsr >> 8) & 1) {
		/* cache operation on I/O addr, tell guest unsupported */
		kvm_inject_dabt(vcpu, vcpu->arch.hxfar);
		return 1;
	}

	if ((vcpu->arch.hsr >> 7) & 1) {
		/* page table accesses IO mem: tell guest to fix its TTBR */
		kvm_inject_dabt(vcpu, vcpu->arch.hxfar);
		return 1;
	}

	switch ((vcpu->arch.hsr >> 22) & 0x3) {
	case 0:
		len = 1;
		break;
	case 1:
		len = 2;
		break;
	case 2:
		len = 4;
		break;
	default:
		kvm_err("Hardware is weird: SAS 0b11 is reserved\n");
		return -EFAULT;
	}

	is_write = vcpu->arch.hsr & HSR_WNR;
	sign_extend = vcpu->arch.hsr & HSR_SSE;
	rt = (vcpu->arch.hsr & HSR_SRT_MASK) >> HSR_SRT_SHIFT;

	if (kvm_vcpu_reg_is_pc(vcpu, rt)) {
		/* IO memory trying to read/write pc */
		kvm_inject_pabt(vcpu, vcpu->arch.hxfar);
		return 1;
	}

	mmio->is_write = is_write;
	mmio->phys_addr = fault_ipa;
	mmio->len = len;
	vcpu->arch.mmio_decode.sign_extend = sign_extend;
	vcpu->arch.mmio_decode.rt = rt;

	/*
	 * The MMIO instruction is emulated and should not be re-executed
	 * in the guest.
	 */
	kvm_skip_instr(vcpu, (vcpu->arch.hsr >> 25) & 1);
	return 0;
}

int io_mem_abort(struct kvm_vcpu *vcpu, struct kvm_run *run,
		 phys_addr_t fault_ipa)
{
	struct kvm_exit_mmio mmio;
	unsigned long rt;
	int ret;

	/*
	 * Prepare MMIO operation. First stash it in a private
	 * structure that we can use for in-kernel emulation. If the
	 * kernel can't handle it, copy it into run->mmio and let user
	 * space do its magic.
	 */

	if (vcpu->arch.hsr & HSR_ISV) {
		ret = decode_hsr(vcpu, fault_ipa, &mmio);
		if (ret)
			return ret;
	} else {
		kvm_err("load/store instruction decoding not implemented\n");
		return -ENOSYS;
	}

	rt = vcpu->arch.mmio_decode.rt;
	trace_kvm_mmio((mmio.is_write) ? KVM_TRACE_MMIO_WRITE :
					 KVM_TRACE_MMIO_READ_UNSATISFIED,
			mmio.len, fault_ipa,
			(mmio.is_write) ? *vcpu_reg(vcpu, rt) : 0);

	if (mmio.is_write)
		memcpy(mmio.data, vcpu_reg(vcpu, rt), mmio.len);

	if (vgic_handle_mmio(vcpu, run, &mmio))
		return 1;

	kvm_prepare_mmio(run, &mmio);
	return 0;
}