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KVM: x86: IN instruction emulation should ignore REP-prefix 

The IN instruction is not be affected by REP-prefix as INS is.  Therefore, the
emulation should ignore the REP prefix as well.  The current emulator
implementation tries to perform writeback when IN instruction with REP-prefix
is emulated. This causes it to perform wrong memory write or spurious #GP
exception to be injected to the guest.

Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Nadav Amit 2014-04-18 03:35:10 +03:00 committed by Marcelo Tosatti
parent 346874c950
commit e6e39f0438
1 changed files with 2 additions and 1 deletions
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3
arch/x86/kvm/emulate.c
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@ -1324,7 +1324,8 @@ static int pio_in_emulated(struct x86_emulate_ctxt *ctxt,
rc->end = n * size; rc->end = n * size;
} }
if (ctxt->rep_prefix && !(ctxt->eflags & EFLG_DF)) { if (ctxt->rep_prefix && (ctxt->d & String) &&
!(ctxt->eflags & EFLG_DF)) {
ctxt->dst.data = rc->data + rc->pos; ctxt->dst.data = rc->data + rc->pos;
ctxt->dst.type = OP_MEM_STR; ctxt->dst.type = OP_MEM_STR;
ctxt->dst.count = (rc->end - rc->pos) / size; ctxt->dst.count = (rc->end - rc->pos) / size;