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Re: [Xen-devel] [PATCH RFC 0/N] xen: arm: rework early bring up

On 09/18/2013 08:24 PM, Ian Campbell wrote:
On Wed, 2013-09-18 at 20:22 +0100, Ian Campbell wrote:
On Wed, 2013-09-18 at 18:33 +0100, Julien Grall wrote:
On 09/17/2013 02:37 AM, Ian Campbell wrote:

The following reworks early bring up on ARM to use a separate set of
boot pagetables. This simplifies things by avoiding the need to bring up
all CPUs in lock step, which in turn allows us to do secondary CPU
bringup in C code.

Unfortunately the main bulk of this change is a single large patch which
is hard to decompose any further since it is basically pulling on the
thread and then knitting a new jumper from it.

With these changes Xen now absolutely requires that the bootloader calls
the hypervisor in HYP mode, the previous workarounds have been removed.
For use on models a bootwrapper is now required. See
         git://xenbits.xen.org/people/ianc/boot-wrapper.git xen-arm32
         git://xenbits.xen.org/people/ianc/boot-wrapper-aarch64.git xen-arm64

I have implemented support for CPU bringup on the fastmodel vexpress
platforms (v7and v8) here, I suppose it should work OK on a real
vexpress too but I've not tried it.

I have just tried the patch series on the versatile express and it
doesn't work. I'm using the u-boot from Andre and all the cpus already
boot in hyp mode (checked without this patch series).


The code should essentially the same as the old kick cpus, but
reimplemented in C. The only difference I can spot is that the C version
is kicking a single CPU at a time while the ASM version is kicking
everyone at once. Does using send_SGI_allbutself instead work as a hack?

Perhaps our idea of the CPUID is wrong or something? Your patches to
fixup the logical CPU id stuff might help?

I have found the issue, in send_SGI_mask we remove the offline CPUs with the following line:
  mask &= cpumask_bits(&cpu_online_map);

As the secondary cpu (assuming we have a board with only 2 cores) is not yet online, we can't send SGI with our code.
I'm very surprised that the code works on the fast models.

To solve the issue, I think we need to create another helper which will send an SGI wihout removing offline CPUs.

You don't happen to still have your vexpress in A7 mode do you?

I'm using the versatile express with only A15 processors enabled.

Julien Grall

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