[PATCH] KVM: x86_emulator: no writeback for bt

[PATCH] KVM: x86_emulator: no writeback for bt

[He, Qing]

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(p.s., this patch is before Laurent's patch of no_wb removal, the change
is minor to adapt to OP_NONE)


Signed-off-by: Qing He <qing.he-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>

---
 drivers/kvm/x86_emulate.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/drivers/kvm/x86_emulate.c b/drivers/kvm/x86_emulate.c
index f294a49..6ab67fe 100644
--- a/drivers/kvm/x86_emulate.c
+++ b/drivers/kvm/x86_emulate.c
@@ -1549,6 +1549,7 @@ twobyte_insn:
 		break;
 	case 0xa3:
 	      bt:		/* bt */
+		no_wb = 1;
 		/* only subword offset */
 		c->src.val &= (c->dst.bytes << 3) - 1;
 		emulate_2op_SrcV_nobyte("bt", c->src, c->dst, _eflags);
-- 
1.5.1.2


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From 4d78d9bf330c478496765184196aeaa085b968a8 Mon Sep 17 00:00:00 2001
From: Qing He <qing.he@intel.com>
Date: Mon, 24 Sep 2007 17:22:13 +0800
Subject: [PATCH] KVM: x86_emulator: no writeback for bt

Signed-off-by: Qing He <qing.he@intel.com>

---
 drivers/kvm/x86_emulate.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/drivers/kvm/x86_emulate.c b/drivers/kvm/x86_emulate.c
index f294a49..6ab67fe 100644
--- a/drivers/kvm/x86_emulate.c
+++ b/drivers/kvm/x86_emulate.c
@@ -1549,6 +1549,7 @@ twobyte_insn:
 		break;
 	case 0xa3:
 	      bt:		/* bt */
+		no_wb = 1;
 		/* only subword offset */
 		c->src.val &= (c->dst.bytes << 3) - 1;
 		emulate_2op_SrcV_nobyte("bt", c->src, c->dst, _eflags);
-- 
1.5.1.2


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Re: [PATCH] KVM: x86_emulator: no writeback for bt

[Avi Kivity]

He, Qing wrote:
> (p.s., this patch is before Laurent's patch of no_wb removal, the change
> is minor to adapt to OP_NONE)
>
>   

Applied, thanks.  Does it solve some specific issue with a guest?  I'll 
have to send it for 2.6.23 as well if it does.

-- 
error compiling committee.c: too many arguments to function


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Re: [PATCH] KVM: x86_emulator: no writeback for bt

[He, Qing]

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>-----Original Message-----
>From: Avi Kivity [mailto:avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org]
>Sent: 2007年9月24日 21:24
>To: He, Qing
>Cc: kvm-devel
>Subject: Re: [kvm-devel] [PATCH] KVM: x86_emulator: no writeback for bt
>
>He, Qing wrote:
>> (p.s., this patch is before Laurent's patch of no_wb removal, the change
>> is minor to adapt to OP_NONE)
>>
>>
>
>Applied, thanks.  Does it solve some specific issue with a guest?  I'll
>have to send it for 2.6.23 as well if it does.

No, it doesn't solve any major issue. We just found that in some occasions, apic irr is written to when this instruction is emulated. It reduces MMIO emulation overhead as well.

>
>--
>error compiling committee.c: too many arguments to function


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