linux-kernel - Re: [PATCH v2 01/11] xen/manage: keep track of the on-going suspend mode

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Date:   Wed, 15 Jul 2020 17:18:08 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Anchal Agarwal <anchalag@...zon.com>
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        x86@...nel.org, jgross@...e.com, linux-pm@...r.kernel.org,
        linux-mm@...ck.org, kamatam@...zon.com, sstabellini@...nel.org,
        konrad.wilk@...cle.com, roger.pau@...rix.com, axboe@...nel.dk,
        davem@...emloft.net, rjw@...ysocki.net, len.brown@...el.com,
        pavel@....cz, peterz@...radead.org, eduval@...zon.com,
        sblbir@...zon.com, xen-devel@...ts.xenproject.org,
        vkuznets@...hat.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, dwmw@...zon.co.uk,
        benh@...nel.crashing.org
Subject: Re: [PATCH v2 01/11] xen/manage: keep track of the on-going suspend
 mode

On 7/15/20 4:49 PM, Anchal Agarwal wrote:
> On Mon, Jul 13, 2020 at 11:52:01AM -0400, Boris Ostrovsky wrote:
>> CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe.
>>
>>
>>
>> On 7/2/20 2:21 PM, Anchal Agarwal wrote:
>>> +
>>> +bool xen_is_xen_suspend(void)
>>
>> Weren't you going to call this pv suspend? (And also --- is this suspend
>> or hibernation? Your commit messages and cover letter talk about fixing
>> hibernation).
>>
>>
> This is for hibernation is for pvhvm/hvm/pv-on-hvm guests as you may call it.
> The method is just there to check if "xen suspend" is in progress.
> I do not see "xen_suspend" differentiating between pv or hvm
> domain until later in the code hence, I abstracted it to xen_is_xen_suspend.


I meant "pv suspend" in the sense that this is paravirtual suspend, not
suspend for paravirtual guests. Just like pv drivers are for both pv and
hvm guests.


And then --- should it be pv suspend or pv hibernation?



>>> +{
>>> +     return suspend_mode == XEN_SUSPEND;
>>> +}
>>> +
>>
>> +static int xen_setup_pm_notifier(void)
>> +{
>> +     if (!xen_hvm_domain())
>> +             return -ENODEV;
>>
>> I forgot --- what did we decide about non-x86 (i.e. ARM)?
> It would be great to support that however, its  out of
> scope for this patch set.
> I’ll be happy to discuss it separately.


I wasn't implying that this *should* work on ARM but rather whether this
will break ARM somehow (because xen_hvm_domain() is true there).



>>
>> And PVH dom0.
> That's another good use case to make it work with however, I still
> think that should be tested/worked upon separately as the feature itself
> (PVH Dom0) is very new.


Same question here --- will this break PVH dom0?


-boris