From mboxrd@z Thu Jan  1 00:00:00 1970
From: Scott Wood <scottwood@freescale.com>
Subject: Re: [PATCH v4 3/3] KVM: PPC: epapr: install ev_idle hcall for e500
 guest
Date: Thu, 16 Feb 2012 10:58:06 -0600
Message-ID: <4F3D359E.6030209@freescale.com>
References: <1329384365-4028-1-git-send-email-yu.liu@freescale.com> <1329384365-4028-2-git-send-email-yu.liu@freescale.com> <1329384365-4028-3-git-send-email-yu.liu@freescale.com> <EAC043A1-A04F-4A27-8488-3C42D99D175E@suse.de>
Mime-Version: 1.0
Content-Type: text/plain; charset="ISO-8859-1"
Content-Transfer-Encoding: 7bit
Cc: Liu Yu <yu.liu@freescale.com>,
	"<kvm-ppc@vger.kernel.org>" <kvm-ppc@vger.kernel.org>,
	"<kvm@vger.kernel.org>" <kvm@vger.kernel.org>,
	"<linuxppc-dev@ozlabs.org>" <linuxppc-dev@ozlabs.org>,
	"<B07421@freescale.com>" <B07421@freescale.com>
To: Alexander Graf <agraf@suse.de>
Return-path: <kvm-ppc-owner@vger.kernel.org>
In-Reply-To: <EAC043A1-A04F-4A27-8488-3C42D99D175E@suse.de>
Sender: kvm-ppc-owner@vger.kernel.org
List-Id: kvm.vger.kernel.org

On 02/16/2012 04:24 AM, Alexander Graf wrote:
> On 16.02.2012, at 10:26, Liu Yu <yu.liu@freescale.com> wrote:
>> +_GLOBAL(epapr_ev_idle)
>> +epapr_ev_idle:
>> +    rlwinm    r3,r1,0,0,31-THREAD_SHIFT    /* current thread_info */
>> +    lwz    r4,TI_LOCAL_FLAGS(r3)    /* set napping bit */
>> +    ori    r4,r4,_TLF_NAPPING    /* so when we take an exception */
>> +    stw    r4,TI_LOCAL_FLAGS(r3)    /* it will return to our caller */
>> +
>> +    wrteei    1
>> +
>> +idle_loop:
>> +    LOAD_REG_IMMEDIATE(r11, HC_VENDOR_EPAPR | HC_EV_IDLE)
>> +
>> +.global epapr_ev_idle_start
>> +epapr_ev_idle_start:
>> +    li    r3, -1
>> +    nop
>> +    nop
>> +    nop
> 
> Can't you just bl into epapr_hypercall_start? You don't even have to save the old lr. because we never return anyways :)

The interrupt will branch to LR, so no, we can't trash it or put it
anywhere else.

-scott