Re: RT Xen on ARM - R-Car series

[Julien Grall <julien.grall@gmail.com>]

[-- Attachment #1.1: Type: text/plain, Size: 1431 bytes --]

Sorry for the formatting.

On Fri, 15 Feb 2019, 18:30 Andrii Anisov, <andrii.anisov@gmail.com> wrote:

> Hello Julien,
>
> On 15.02.19 18:31, Julien Grall wrote:
> > Why? Is it because you want to be cache-aligned?  If so, requiring the
> > structure to be 64-bytes is not enough.
>
> I did not mean caches.
>

What is the reason then?

> You also want the address to
> > be 64-bytes aligned.
>
> I would keep it as a hint for static/dynamic allocations in VMs, hoping
> the address would be normally 64 bytes aligned.
> I hope it might be stronger than, only commenting it should not cross a
> page boundary. E.g. like `struct vcpu_register_vcpu_info` is commented.
>
> I've got this idea after looking at runstate definition as per-cpu in
> Linux [1]
>

It is not obvious why it would be 64-bytes alignment from the definition.
Can you please explain the rationale to impose that alignment?

I really appreciate you suggest ideas/patches but  it would be helpful if
you provide rationale at the same time. This would avoid a round of e-mails
just for asking the reasons and delay the interesting bits.


> > If an OS cares about it, then it can aligned itself here.
> I suppose we can hint the OS by structure alignment in the interface
> header, and require it from OS verifying it on hypercall handling

.


> [1]
> https://elixir.bootlin.com/linux/v5.0-rc6/source/drivers/xen/time.c#L22
>
> --
> Sincerely,
> Andrii Anisov.
>

[-- Attachment #1.2: Type: text/html, Size: 2554 bytes --]

[-- Attachment #2: Type: text/plain, Size: 157 bytes --]

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel