From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julien Grall Subject: Re: [PATCH] xen/arm64: Avoid sending SGI when kicking secondary cpus with spin_table Date: Wed, 15 Apr 2015 18:53:57 +0100 Message-ID: <552EA5B5.9090008@citrix.com> References: <1428392032-11551-1-git-send-email-cbz@baozis.org> <55251DB1.6050504@citrix.com> <1429109864.15516.318.camel@citrix.com> <552E8A3D.3070700@gmail.com> <1429114884.25195.5.camel@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1429114884.25195.5.camel@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Ian Campbell Cc: Julien Grall , Chen Baozi , Chen Baozi , julien.grall@linaro.org, xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On 15/04/2015 17:21, Ian Campbell wrote: > On Wed, 2015-04-15 at 16:56 +0100, Julien Grall wrote: >> Hi Ian, >> >> On 15/04/15 15:57, Ian Campbell wrote: >>> On Wed, 2015-04-08 at 13:23 +0100, Julien Grall wrote: >>>> Hi Chen, >>>> >>>> Subject: I think you can drop the "_" in spin_table. >>>> >>>> On 07/04/15 08:33, Chen Baozi wrote: >>>>> From: Chen Baozi >>>>> >>>>> On arm64, either firmware or xen's smp_up_cpu gate uses WFE on secondary >>>>> cpus to stand-by when booting. Thus, using SEV is enough for the boot >>>>> cpu to kick other secondaries. Further more, the current implementation >>>>> of cpu_up_send_sgi would pass a NULL cpumask pointer to send_SGI, which >>>>> then lead a data fault on GICv3 send_SGI implementation. >>>> >>>> I'm not familiar with spin table on ARM64, so I will let Ian answer >>>> about it. >>> >>> For arm32 it's sadly all a bit adhoc and not terribly well documented. >>> (If I'm wrong I'd love a pointer to the doc). But for arm64 it does seem >>> to be documented (linux/Documentation/arm64/booting.txt) >> >> Thanks for the pointer. >> >> [..] >> >>> So, I dunno, it seems like there is a good chance we could remove this, >>> but that might break some random platform which we have forgotten about. >> >> Hmmm... I looked the wrong code in Linux :/. >> The SGI is required for most of the platforms. > > Could you give a pointer to that code please. > > -- Julien Grall