diff options
Diffstat (limited to 'arch/x86/kvm/emulate.c')
| -rw-r--r-- | arch/x86/kvm/emulate.c | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index e8c03be83e48..9b655d113fc6 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -2570,6 +2570,30 @@ static bool emulator_io_permited(struct x86_emulate_ctxt *ctxt, return true; } +static void string_registers_quirk(struct x86_emulate_ctxt *ctxt) +{ + /* + * Intel CPUs mask the counter and pointers in quite strange + * manner when ECX is zero due to REP-string optimizations. + */ +#ifdef CONFIG_X86_64 + if (ctxt->ad_bytes != 4 || !vendor_intel(ctxt)) + return; + + *reg_write(ctxt, VCPU_REGS_RCX) = 0; + + switch (ctxt->b) { + case 0xa4: /* movsb */ + case 0xa5: /* movsd/w */ + *reg_rmw(ctxt, VCPU_REGS_RSI) &= (u32)-1; + /* fall through */ + case 0xaa: /* stosb */ + case 0xab: /* stosd/w */ + *reg_rmw(ctxt, VCPU_REGS_RDI) &= (u32)-1; + } +#endif +} + static void save_state_to_tss16(struct x86_emulate_ctxt *ctxt, struct tss_segment_16 *tss) { @@ -4910,6 +4934,7 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt) if (ctxt->rep_prefix && (ctxt->d & String)) { /* All REP prefixes have the same first termination condition */ if (address_mask(ctxt, reg_read(ctxt, VCPU_REGS_RCX)) == 0) { + string_registers_quirk(ctxt); ctxt->eip = ctxt->_eip; ctxt->eflags &= ~X86_EFLAGS_RF; goto done; |