This patch modifies the management of REX prefix according behavior I saw in Xen 3.1. In Xen, this modification has been introduced by Jan Beulich.
http://lists.xensource.com/archives/html/xen-changelog/2007-01/msg00081.html Signed-off-by: Laurent Vivier <[EMAIL PROTECTED]> --- drivers/kvm/x86_emulate.c | 23 +++++++++++++++-------- 1 files changed, 15 insertions(+), 8 deletions(-) diff --git a/drivers/kvm/x86_emulate.c b/drivers/kvm/x86_emulate.c index f8516ba..585cccf 100644 --- a/drivers/kvm/x86_emulate.c +++ b/drivers/kvm/x86_emulate.c @@ -552,7 +552,7 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops) } /* Legacy prefixes. */ - for (i = 0; i < 8; i++) { + for (;;) { switch (c->b = insn_fetch(u8, 1, c->eip)) { case 0x66: /* operand-size override */ c->op_bytes ^= 6; /* switch between 2/4 bytes */ @@ -583,6 +583,11 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops) case 0x36: /* SS override */ c->override_base = &ctxt->ss_base; break; + case 0x40 ... 0x4f: /* REX */ + if (mode != X86EMUL_MODE_PROT64) + goto done_prefixes; + rex_prefix = c->b; + continue; case 0xf0: /* LOCK */ c->lock_prefix = 1; break; @@ -593,19 +598,21 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops) default: goto done_prefixes; } + + /* Any legacy prefix after a REX prefix nullifies its effect. */ + + rex_prefix = 0; } done_prefixes: /* REX prefix. */ - if ((mode == X86EMUL_MODE_PROT64) && ((c->b & 0xf0) == 0x40)) { - rex_prefix = c->b; - if (c->b & 8) + if (rex_prefix) { + if (rex_prefix & 8) c->op_bytes = 8; /* REX.W */ - c->modrm_reg = (c->b & 4) << 1; /* REX.R */ - index_reg = (c->b & 2) << 2; /* REX.X */ - c->modrm_rm = base_reg = (c->b & 1) << 3; /* REG.B */ - c->b = insn_fetch(u8, 1, c->eip); + c->modrm_reg = (rex_prefix & 4) << 1; /* REX.R */ + index_reg = (rex_prefix & 2) << 2; /* REX.X */ + c->modrm_rm = base_reg = (rex_prefix & 1) << 3; /* REG.B */ } /* Opcode byte(s). */ -- 1.5.2.4 ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ kvm-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/kvm-devel
