[PATCH 18/25] KVM: emulate: do not initialize memopp

From: Paolo Bonzini
Date: Mon Jun 09 2014 - 09:02:26 EST


From: Bandan Das <bsd@xxxxxxxxxx>

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@xxxxxxxxxx>
[Fix immediate operands with rip-relative addressing. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
arch/x86/include/asm/kvm_emulate.h | 5 +++++
arch/x86/kvm/emulate.c | 8 ++++----
2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
index 268bbd4aae99..692b0bfadf91 100644
--- a/arch/x86/include/asm/kvm_emulate.h
+++ b/arch/x86/include/asm/kvm_emulate.h
@@ -322,6 +322,11 @@ 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;
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 05f7bb416fc2..32f38a3467a0 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1176,6 +1176,9 @@ 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;
}
@@ -4499,9 +4502,6 @@ 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.
@@ -4522,7 +4522,7 @@ 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;
--
1.8.3.1


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/