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KVM: emulate: do not initialize memopp 

rip_relative is only set if decode_modrm runs, and if you have ModRM
you will also have a memopp.  We can then access memopp unconditionally.
Note that rip_relative cannot be hoisted up to decode_modrm, or you
break "mov $0, xyz(%rip)".

Also, move typecast on "out of range value" of mem.ea to decode_modrm.

Together, all these optimizations save about 50 cycles on each emulated
instructions (4-6%).

Signed-off-by: Bandan Das <bsd@redhat.com>
[Fix immediate operands with rip-relative addressing. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Bandan Das 2014-04-16 12:46:14 -04:00 committed by Paolo Bonzini
parent 573e80fe04
commit 41061cdb98
2 changed files with 9 additions and 4 deletions
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5
arch/x86/include/asm/kvm_emulate.h
View File

@ -295,6 +295,11 @@ struct x86_emulate_ctxt {
struct operand dst;
int (*execute)(struct x86_emulate_ctxt *ctxt);
int (*check_perm)(struct x86_emulate_ctxt *ctxt);
/*
* The following six fields are cleared together,
* the rest are initialized unconditionally in x86_decode_insn
* or elsewhere
*/
bool rip_relative;
u8 rex_prefix;
u8 lock_prefix;

8
arch/x86/kvm/emulate.c
View File

@ -1177,6 +1177,9 @@ static int decode_modrm(struct x86_emulate_ctxt *ctxt,
}
}
op->addr.mem.ea = modrm_ea;
if (ctxt->ad_bytes != 8)
ctxt->memop.addr.mem.ea = (u32)ctxt->memop.addr.mem.ea;
done:
return rc;
}
@ -4425,9 +4428,6 @@ done_prefixes:
ctxt->memop.addr.mem.seg = ctxt->seg_override;
if (ctxt->memop.type == OP_MEM && ctxt->ad_bytes != 8)
ctxt->memop.addr.mem.ea = (u32)ctxt->memop.addr.mem.ea;
/*
* Decode and fetch the source operand: register, memory
* or immediate.
@ -4448,7 +4448,7 @@ done_prefixes:
rc = decode_operand(ctxt, &ctxt->dst, (ctxt->d >> DstShift) & OpMask);
done:
if (ctxt->memopp && ctxt->memopp->type == OP_MEM && ctxt->rip_relative)
if (ctxt->rip_relative)
ctxt->memopp->addr.mem.ea += ctxt->_eip;
return (rc != X86EMUL_CONTINUE) ? EMULATION_FAILED : EMULATION_OK;