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Bug#964845: Any Update

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Hi Ben,

It's true that the hypervisor can save the guest state and restore it later
without the help from the guest kernel.

However, to make the user space applications in the guest (like the network
daemons) aware of the suspend/resume, we want the entire suspend to RAM
process (begins with hypervisor asserting SLPBTN_STS [1] and ends with
guest kernel asserting SLP_TYP0 [2]) to run into completion so that guest
OS can be prepared for the issues caused by the suspend/resume (e.g. the
time jump). The write to SLP_TYP0 also serves as an acknowledgement from
the guest OS that the sleep request has been processed successfully by the
guest, the hypervisor can then start the saving of the guest state.

Daemons like acpid and systemd seem to also need "mem" to be included in
/sys/power/state in order to respond to SLPBTN_STS [1] and I think whether
"mem" is in /sys/power/state is controlled by the CONFIG_SUSPEND.

[1] ACPI 4.0 <https://uefi.org/sites/default/files/resources/ACPI_4.pdf>
4.7.3.1.1
[2] ACPI 4.0 <https://uefi.org/sites/default/files/resources/ACPI_4.pdf>
4.7.3.2.1


On Wed, Oct 28, 2020 at 2:24 PM Ben Hutchings <ben@decadent.org.uk> wrote:

> Control: tag -1 moreinfo
>
> On Wed, 2020-10-28 at 12:29 -0700, Wanli Li wrote:
> > Hi, just wanted to know whether there's any update on this feature
> request?
>
> Why would this be needed in a cloud deployment?  Hypervisors should be
> able to suspend and resume guests without specific support in the guest
> kernel.
>
> Ben.
>
> --
> Ben Hutchings
> You can't have everything.  Where would you put it?
>
>
>

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Thread

Bug#964845: Please enable CONFIG_SUSPEND in the cloud image kernel Wanli Li <liwanli@google.com> - 2020-07-11 01:10 +0200
  Bug#964845: Any Update Wanli Li <liwanli@google.com> - 2020-10-28 20:40 +0100
    Bug#964845: Any Update Ben Hutchings <ben@decadent.org.uk> - 2020-10-28 22:30 +0100
      Bug#964845: Any Update Wanli Li <liwanli@google.com> - 2020-10-28 23:40 +0100
  Processed: Re: Bug#964845: Any Update "Debian Bug Tracking System" <owner@bugs.debian.org> - 2020-10-28 22:30 +0100
  Bug#964845: marked as done (Please enable CONFIG_SUSPEND in the  cloud image kernel) "Debian Bug Tracking System" <owner@bugs.debian.org> - 2021-01-21 15:20 +0100

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