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Re: [Xen-devel] [PATCH 02/18] xen/arm: Implement PSCI system suspend call (virtual interface)

On Wed, 14 Nov 2018, Julien Grall wrote:
> On 13/11/2018 20:39, Stefano Stabellini wrote:
> > On Tue, 13 Nov 2018, Julien Grall wrote:
> > 
> > If we mark the domU simply as "paused" it will be difficult to implement
> > correctly "xl restore" / "xl trigger s3resume". We should be able to
> > distinguish a domain which is simply not running or paused (as in "xl
> > pause") from one that has been put to sleep.  Otherwise we won't be able
> > to use "xl pause" in its original sense anymore. "xl pause" will become
> > effectively "xl trigger sleep" on ARM. Which is something to consider
> > but I don't think that is what we want.
> I didn't suggested to only use those 2 helpers. But you can build
> suspend/resume on top of it. AFAICT, this is how s3 suspend/resume works on
> x86 HVM.

Sounds like we are saying the same thing.

> > The most similar feature is ACPI S3 in x86-land but the current calls
> > are so ACPI/x86 specific that don't make much sense on a ACPI-less ARM
> > implementation. If I am not mistaken, on x86 there is a special struct
> > domain flag for this: d->arch.hvm.is_s3_suspended.
> > 
> > 
> > Let's leave aside the "which commands should we use" discussion for now
> > because it doesn't related to this patch series. It seems to me that the
> > best option is to introduce a new ARM specific struct domain flag,
> > something akin to d->arch.hvm.is_s3_suspended but ARM PSCI specific.
> See above.
> -- 
> Julien Grall

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