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





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 <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.



--
Julien Grall

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