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linux-next/arch/arm/kvm/mmio.c
Andre Przywara 5100f9833e arm/arm64: KVM: avoid unnecessary guest register mangling on MMIO read
Currently we mangle the endianness of the guest's register even on an
MMIO _read_, where it is completely useless, because we will not use
the value of that register.
Rework the io_mem_abort() function to clearly separate between reads
and writes and only do the endianness mangling on MMIO writes.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
2014-11-25 13:57:28 +00:00

209 lines
4.6 KiB
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"
static void mmio_write_buf(char *buf, unsigned int len, unsigned long data)
{
void *datap = NULL;
union {
u8 byte;
u16 hword;
u32 word;
u64 dword;
} tmp;
switch (len) {
case 1:
tmp.byte = data;
datap = &tmp.byte;
break;
case 2:
tmp.hword = data;
datap = &tmp.hword;
break;
case 4:
tmp.word = data;
datap = &tmp.word;
break;
case 8:
tmp.dword = data;
datap = &tmp.dword;
break;
}
memcpy(buf, datap, len);
}
static unsigned long mmio_read_buf(char *buf, unsigned int len)
{
unsigned long data = 0;
union {
u16 hword;
u32 word;
u64 dword;
} tmp;
switch (len) {
case 1:
data = buf[0];
break;
case 2:
memcpy(&tmp.hword, buf, len);
data = tmp.hword;
break;
case 4:
memcpy(&tmp.word, buf, len);
data = tmp.word;
break;
case 8:
memcpy(&tmp.dword, buf, len);
data = tmp.dword;
break;
}
return data;
}
/**
* 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 data;
unsigned int len;
int mask;
if (!run->mmio.is_write) {
len = run->mmio.len;
if (len > sizeof(unsigned long))
return -EINVAL;
data = mmio_read_buf(run->mmio.data, len);
if (vcpu->arch.mmio_decode.sign_extend &&
len < sizeof(unsigned long)) {
mask = 1U << ((len * 8) - 1);
data = (data ^ mask) - mask;
}
trace_kvm_mmio(KVM_TRACE_MMIO_READ, len, run->mmio.phys_addr,
data);
data = vcpu_data_host_to_guest(vcpu, data, len);
*vcpu_reg(vcpu, vcpu->arch.mmio_decode.rt) = data;
}
return 0;
}
static int decode_hsr(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
struct kvm_exit_mmio *mmio)
{
unsigned long rt;
int len;
bool is_write, sign_extend;
if (kvm_vcpu_dabt_isextabt(vcpu)) {
/* cache operation on I/O addr, tell guest unsupported */
kvm_inject_dabt(vcpu, kvm_vcpu_get_hfar(vcpu));
return 1;
}
if (kvm_vcpu_dabt_iss1tw(vcpu)) {
/* page table accesses IO mem: tell guest to fix its TTBR */
kvm_inject_dabt(vcpu, kvm_vcpu_get_hfar(vcpu));
return 1;
}
len = kvm_vcpu_dabt_get_as(vcpu);
if (unlikely(len < 0))
return len;
is_write = kvm_vcpu_dabt_iswrite(vcpu);
sign_extend = kvm_vcpu_dabt_issext(vcpu);
rt = kvm_vcpu_dabt_get_rd(vcpu);
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, kvm_vcpu_trap_il_is32bit(vcpu));
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 data;
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 (kvm_vcpu_dabt_isvalid(vcpu)) {
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;
if (mmio.is_write) {
data = vcpu_data_guest_to_host(vcpu, *vcpu_reg(vcpu, rt),
mmio.len);
trace_kvm_mmio(KVM_TRACE_MMIO_WRITE, mmio.len,
fault_ipa, data);
mmio_write_buf(mmio.data, mmio.len, data);
} else {
trace_kvm_mmio(KVM_TRACE_MMIO_READ_UNSATISFIED, mmio.len,
fault_ipa, 0);
}
if (vgic_handle_mmio(vcpu, run, &mmio))
return 1;
kvm_prepare_mmio(run, &mmio);
return 0;
}