When the old value and new one are the same the emulator skips the
write; this is undesirable when the destination is a MMIO area and the
write shall be performed regardless of the previous value. This
optimization breaks e.g. a Linux guest APIC compiled without
X86_GOOD_APIC.
Remove the check and perform the writeback stage in the emulation unless
it's explicitly disabled (currently push and some 2 bytes instructions
may disable the writeback).
Signed-Off-By: Luca Tettamanti <kronos.it@gmail.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
int mode = ctxt->mode;
unsigned long modrm_ea;
int use_modrm_ea, index_reg = 0, base_reg = 0, scale, rip_relative = 0;
int mode = ctxt->mode;
unsigned long modrm_ea;
int use_modrm_ea, index_reg = 0, base_reg = 0, scale, rip_relative = 0;
/* Shadow copy of register state. Committed on successful emulation. */
unsigned long _regs[NR_VCPU_REGS];
/* Shadow copy of register state. Committed on successful emulation. */
unsigned long _regs[NR_VCPU_REGS];
_regs[VCPU_REGS_RSP]),
&dst.val, dst.bytes, ctxt)) != 0)
goto done;
_regs[VCPU_REGS_RSP]),
&dst.val, dst.bytes, ctxt)) != 0)
goto done;
- dst.val = dst.orig_val; /* skanky: disable writeback */
break;
default:
goto cannot_emulate;
break;
default:
goto cannot_emulate;
- if ((d & Mov) || (dst.orig_val != dst.val)) {
switch (dst.type) {
case OP_REG:
/* The 4-byte case *is* correct: in 64-bit mode we zero-extend. */
switch (dst.type) {
case OP_REG:
/* The 4-byte case *is* correct: in 64-bit mode we zero-extend. */
goto done;
register_address_increment(_regs[VCPU_REGS_RSP], op_bytes);
goto done;
register_address_increment(_regs[VCPU_REGS_RSP], op_bytes);
- dst.orig_val = dst.val; /* Disable writeback. */
+ no_wb = 1; /* Disable writeback. */
twobyte_special_insn:
/* Disable writeback. */
twobyte_special_insn:
/* Disable writeback. */
- dst.orig_val = dst.val;
switch (b) {
case 0x09: /* wbinvd */
break;
switch (b) {
case 0x09: /* wbinvd */
break;