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

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.

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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