Re: [Xen-devel] [PATCH] xen/arm64: Avoid sending SGI when kicking secondary cpus with spin_table

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

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 <baozich@xxxxxxxxx>
> >>>
> >>> 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.



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