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From:   "Rafael J. Wysocki" <rafael@kernel.org>
Date:   Fri, 31 Jul 2020 16:25:12 +0200
Message-ID: <CAJZ5v0j2kqgEfbiQchiA_USwGKC-UFkn2J3bUU2xCWU=+1p9Mw@mail.gmail.com>
Subject: Re: [PATCH v2 01/11] xen/manage: keep track of the on-going suspend mode
To:     Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc:     Anchal Agarwal <anchalag@amazon.com>,
        Stefano Stabellini <sstabellini@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        "the arch/x86 maintainers" <x86@kernel.org>,
        Juergen Gross <jgross@suse.com>,
        Linux PM <linux-pm@vger.kernel.org>,
        Linux Memory Management List <linux-mm@kvack.org>,
        "Kamata, Munehisa" <kamatam@amazon.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        roger.pau@citrix.com, Jens Axboe <axboe@kernel.dk>,
        David Miller <davem@davemloft.net>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>,
        Peter Zijlstra <peterz@infradead.org>,
        Eduardo Valentin <eduval@amazon.com>,
        "Singh, Balbir" <sblbir@amazon.com>,
        xen-devel@lists.xenproject.org,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        netdev <netdev@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        David Woodhouse <dwmw@amazon.co.uk>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>
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On Fri, Jul 31, 2020 at 4:14 PM Boris Ostrovsky
<boris.ostrovsky@oracle.com> wrote:
>
> On 7/30/20 7:06 PM, Anchal Agarwal wrote:
> > On Mon, Jul 27, 2020 at 06:08:29PM -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 7/24/20 7:01 PM, Stefano Stabellini wrote:
> >>> Yes, it does, thank you. I'd rather not introduce unknown regressions so
> >>> I would recommend to add an arch-specific check on registering
> >>> freeze/thaw/restore handlers. Maybe something like the following:
> >>>
> >>> #ifdef CONFIG_X86
> >>>     .freeze = blkfront_freeze,
> >>>     .thaw = blkfront_restore,
> >>>     .restore = blkfront_restore
> >>> #endif
> >>>
> >>>
> >>> maybe Boris has a better suggestion on how to do it
> >>
> >> An alternative might be to still install pm notifier in
> >> drivers/xen/manage.c (I think as result of latest discussions we decided
> >> we won't need it) and return -ENOTSUPP for ARM for
> >> PM_HIBERNATION_PREPARE and friends. Would that work?
> >>
> > I think the question here is for registering driver specific freeze/thaw/restore
> > callbacks for x86 only. I have dropped the pm_notifier in the v3 still pending
> > testing. So I think just registering driver specific callbacks for x86 only is a
> > good option. What do you think?
>
>
> I suggested using the notifier under assumption that if it returns an
> error then that will prevent callbacks to be called because hibernation
> will be effectively disabled.

That's correct.