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From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
To: "Agarwal, Anchal" <anchalag@amazon.com>,
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	"Kamata, Munehisa" <kamatam@amazon.com>,
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	"Woodhouse, David" <dwmw@amazon.co.uk>,
	"benh@kernel.crashing.org" <benh@kernel.crashing.org>
Subject: Re: [PATCH 04/12] x86/xen: add system core suspend and resume callbacks
Date: Fri, 5 Jun 2020 17:24:37 -0400	[thread overview]
Message-ID: <e2073aa4-2410-4630-fee6-4e4abc172876@oracle.com> (raw)
In-Reply-To: <B966B3A2-4F08-42FA-AF59-B8AA0783C2BA@amazon.com>

On 6/3/20 6:40 PM, Agarwal, Anchal 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 5/19/20 7:26 PM, Anchal Agarwal wrote:
>     > From: Munehisa Kamata <kamatam@amazon.com>
>     >
>     > Add Xen PVHVM specific system core callbacks for PM suspend and
>     > hibernation support. The callbacks suspend and resume Xen
>     > primitives,like shared_info, pvclock and grant table. Note that
>     > Xen suspend can handle them in a different manner, but system
>     > core callbacks are called from the context.
>
>
>     I don't think I understand that last sentence.
>
> Looks like it may have cryptic meaning of stating that xen_suspend calls syscore_suspend from xen_suspend
> So, if these syscore ops gets called  during xen_suspend do not do anything. Check if the mode is in xen suspend 
> and return from there. These syscore_ops are specifically for domU hibernation.
> I must admit, I may have overlooked lack of explanation of some implicit details in the original commit msg. 
>
>     >  So if the callbacks
>     > are called from Xen suspend context, return immediately.
>     >
>
>
>     > +
>     > +static int xen_syscore_suspend(void)
>     > +{
>     > +     struct xen_remove_from_physmap xrfp;
>     > +     int ret;
>     > +
>     > +     /* Xen suspend does similar stuffs in its own logic */
>     > +     if (xen_suspend_mode_is_xen_suspend())
>     > +             return 0;


With your explanation now making this clearer, is this check really
necessary? From what I see we are in XEN_SUSPEND mode when
lock_system_sleep() lock is taken, meaning that we can't initialize
hibernation.


>     > +
>     > +     xrfp.domid = DOMID_SELF;
>     > +     xrfp.gpfn = __pa(HYPERVISOR_shared_info) >> PAGE_SHIFT;
>     > +
>     > +     ret = HYPERVISOR_memory_op(XENMEM_remove_from_physmap, &xrfp);
>     > +     if (!ret)
>     > +             HYPERVISOR_shared_info = &xen_dummy_shared_info;
>     > +
>     > +     return ret;
>     > +}
>     > +
>     > +static void xen_syscore_resume(void)
>     > +{
>     > +     /* Xen suspend does similar stuffs in its own logic */
>     > +     if (xen_suspend_mode_is_xen_suspend())
>     > +             return;
>     > +
>     > +     /* No need to setup vcpu_info as it's already moved off */
>     > +     xen_hvm_map_shared_info();
>     > +
>     > +     pvclock_resume();
>     > +
>     > +     gnttab_resume();
>
>
>     Do you call gnttab_suspend() in pm suspend path?
> No, since it does nothing for HVM guests. The unmap_frames is only applicable for PV guests right?


You should call it nevertheless. It will decide whether or not anything
needs to be done.


-boris




  reply	other threads:[~2020-06-05 21:25 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-19 23:24 [PATCH 00/12] Fix PM hibernation in Xen guests Anchal Agarwal
2020-05-19 23:24 ` [PATCH 01/12] xen/manage: keep track of the on-going suspend mode Anchal Agarwal
2020-05-30 22:26   ` Boris Ostrovsky
2020-06-01 21:00     ` Agarwal, Anchal
2020-06-01 22:39       ` Boris Ostrovsky
2020-05-19 23:25 ` [PATCH 02/12] xenbus: add freeze/thaw/restore callbacks support Anchal Agarwal
2020-05-30 22:56   ` Boris Ostrovsky
2020-06-01 23:36     ` Agarwal, Anchal
2020-05-19 23:25 ` [PATCH 03/12] x86/xen: Introduce new function to map HYPERVISOR_shared_info on Resume Anchal Agarwal
2020-05-30 23:02   ` Boris Ostrovsky
2020-06-04 23:03     ` Anchal Agarwal
2020-06-05 21:39       ` Boris Ostrovsky
2020-06-08 16:52         ` Anchal Agarwal
2020-06-08 18:49           ` Boris Ostrovsky
2020-05-19 23:26 ` [PATCH 04/12] x86/xen: add system core suspend and resume callbacks Anchal Agarwal
2020-05-30 23:10   ` Boris Ostrovsky
2020-06-03 22:40     ` Agarwal, Anchal
2020-06-05 21:24       ` Boris Ostrovsky [this message]
2020-06-08 17:09         ` Anchal Agarwal
2020-05-19 23:26 ` [PATCH 05/12] genirq: Shutdown irq chips in suspend/resume during hibernation Anchal Agarwal
2020-05-19 23:29   ` Singh, Balbir
2020-05-19 23:36     ` Agarwal, Anchal
2020-05-19 23:34   ` Anchal Agarwal
2020-05-30 23:17   ` Boris Ostrovsky
2020-06-01 20:46     ` Agarwal, Anchal
2020-05-19 23:27 ` [PATCH 06/12] xen-blkfront: add callbacks for PM suspend and hibernation Anchal Agarwal
2020-05-20  5:00   ` kbuild test robot
2020-05-20  5:07   ` kbuild test robot
2020-05-21 23:48   ` Anchal Agarwal
2020-05-22  1:43     ` Singh, Balbir
2020-05-23 12:32   ` kbuild test robot
2020-05-28 12:30   ` Roger Pau Monné
2020-05-19 23:28 ` [PATCH 07/12] xen-netfront: " Anchal Agarwal
2020-05-19 23:28 ` [PATCH 08/12] xen/time: introduce xen_{save,restore}_steal_clock Anchal Agarwal
2020-05-30 23:32   ` Boris Ostrovsky
2020-05-19 23:28 ` [PATCH 09/12] x86/xen: save and restore steal clock Anchal Agarwal
2020-05-30 23:44   ` Boris Ostrovsky
2020-06-04 18:33     ` Anchal Agarwal
2020-05-19 23:29 ` [PATCH 10/12] xen: Introduce wrapper for save/restore sched clock offset Anchal Agarwal
2020-05-19 23:29 ` [PATCH 11/12] xen: Update sched clock offset to avoid system instability in hibernation Anchal Agarwal
2020-05-19 23:29 ` [PATCH 12/12] PM / hibernate: update the resume offset on SNAPSHOT_SET_SWAP_AREA Anchal Agarwal
2020-05-28 17:59 ` [PATCH 00/12] Fix PM hibernation in Xen guests Agarwal, Anchal

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