linux-kernel - Re: [PATCH v2 00/10] LUO: PCI subsystem (phase I)

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Message-ID: <mafs01pn6nbse.fsf@kernel.org>
Date: Mon, 13 Oct 2025 15:58:41 +0200
From: Pratyush Yadav <pratyush@...nel.org>
To: Jason Miu <jasonmiu@...gle.com>
Cc: Chris Li <chrisl@...nel.org>,  Pratyush Yadav <pratyush@...nel.org>,
  Bjorn Helgaas <helgaas@...nel.org>,  Pasha Tatashin
 <pasha.tatashin@...een.com>,  Bjorn Helgaas <bhelgaas@...gle.com>,  Greg
 Kroah-Hartman <gregkh@...uxfoundation.org>,  "Rafael J. Wysocki"
 <rafael@...nel.org>,  Danilo Krummrich <dakr@...nel.org>,  Len Brown
 <lenb@...nel.org>,  linux-kernel@...r.kernel.org,
  linux-pci@...r.kernel.org,  linux-acpi@...r.kernel.org,  David Matlack
 <dmatlack@...gle.com>,  Pasha Tatashin <tatashin@...gle.com>,  Vipin
 Sharma <vipinsh@...gle.com>,  Saeed Mahameed <saeedm@...dia.com>,  Adithya
 Jayachandran <ajayachandra@...dia.com>,  Parav Pandit <parav@...dia.com>,
  William Tu <witu@...dia.com>,  Mike Rapoport <rppt@...nel.org>,  Jason
 Gunthorpe <jgg@...pe.ca>,  Leon Romanovsky <leon@...nel.org>,
  skhawaja@...gle.com
Subject: Re: [PATCH v2 00/10] LUO: PCI subsystem (phase I)

On Fri, Oct 10 2025, Jason Miu wrote:

> On Thu, Oct 9, 2025 at 9:19 PM Chris Li <chrisl@...nel.org> wrote:
>>
>> On Thu, Oct 9, 2025 at 4:21 PM Pratyush Yadav <pratyush@...nel.org> wrote:
>> >
>> > On Tue, Oct 07 2025, Chris Li wrote:
>> >
>> > [...]
>> > > That will keep me busy for a while waiting for the VFIO series.
>> >
>> > I recall we talked in one of the biweekly meetings about some sanity
>> > checking of folios right before reboot (make sure they are right order,
>> > etc.) under a KEXEC_HANDOVER_DEBUG option. If you have some spare time
>> > on your hands, would be cool to see some patches for that as well :-)
>>
>> Sure, I will add that to my "nice to have" list. No promised I got
>> time to get to it with the PCI. It belong to the KHO series not PCI
>> though.
>>

Right. It is only a "nice to have", and not a requirement. And certainly
not for the PCI series.

>
> Hi Pratyush, Chris,
>
> For the folio sanity check with KEXEC_HANDOVER_DEBUG, I can follow
> that up. Would you tell me what we like to check before reboot, I may
> have missed some context. Thanks!

The idea is to sanity-check the preserved folios in the kexec-reboot
flow somewhere. The main check discussed was to make sure the folios are
of the same order as they were preserved with. This will help catch bugs
where folios might split after being preserved.

Maybe we can add some more checks too? Like making sure the folios
aren't freed after they were preserved. But that condition is a bit
trickier to catch. But at least the former should be simple enough to
do as a start.

-- 
Regards,
Pratyush Yadav