From: Bjorn Helgaas <helgaas@kernel.org>
To: David Matlack <dmatlack@google.com>
Cc: sashiko-reviews@lists.linux.dev, linux-pci@vger.kernel.org
Subject: Re: [PATCH v5 02/11] PCI: liveupdate: Track outgoing preserved PCI devices
Date: Fri, 22 May 2026 12:57:55 -0500 [thread overview]
Message-ID: <20260522175755.GA231746@bhelgaas> (raw)
In-Reply-To: <agYRd0xQs0r8OOKA@google.com>
On Thu, May 14, 2026 at 06:16:23PM +0000, David Matlack wrote:
> On 2026-05-14 12:31 AM, sashiko-bot@kernel.org wrote:
> ...
> > > static void pci_flb_unpreserve(struct liveupdate_flb_op_args *args)
> > > {
> > > - struct pci_ser *ser = args->obj;
> > > + struct pci_flb_outgoing *outgoing = args->obj;
> > >
> > > - WARN_ON_ONCE(ser->nr_devices);
> > > - kho_unpreserve_free(ser);
> > > + WARN_ON_ONCE(outgoing->ser->nr_devices);
> > > + kho_unpreserve_free(outgoing->ser);
> > > + kfree(outgoing);
> >
> > If a driver fails to unpreserve a device before the FLB is torn down, this
> > WARN_ON_ONCE triggers, but the memory is still freed.
> >
> > Does this leave dev->liveupdate.outgoing pointing to freed memory?
>
> Yes, if a driver unpreserves a device without notifying the PCI core
> then that would lead to the PCI core having a pointer to freed memory.
Just a curiosity, I guess: How is this possible? Is the driver
responsible for doing a generic unpreserve and also a PCI unpreserve?
Seems like it should do a single unpreserve, which should internally
take care of whatever PCI/IOMMU/etc unpreserve is needed.
I guess the requirement is explained in "[02/11] PCI: liveupdate:
Track outgoing ...":
+ * ... Drivers must call
+ * pci_liveupdate_unpreserve() from their struct liveupdate_file_handler
+ * unpreserve() callback to ensure the outgoing struct pci_ser is allocated.
I just don't know what the driver changes will look like.
next prev parent reply other threads:[~2026-05-22 17:57 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-12 18:48 [PATCH v5 00/11] PCI: liveupdate: PCI core support for Live Update David Matlack
2026-05-12 18:48 ` [PATCH v5 01/11] PCI: liveupdate: Set up FLB handler for the PCI core David Matlack
2026-05-12 18:48 ` [PATCH v5 02/11] PCI: liveupdate: Track outgoing preserved PCI devices David Matlack
2026-05-14 0:31 ` sashiko-bot
2026-05-14 18:16 ` David Matlack
2026-05-22 17:57 ` Bjorn Helgaas [this message]
2026-05-22 18:07 ` David Matlack
2026-05-12 18:48 ` [PATCH v5 03/11] PCI: liveupdate: Track incoming " David Matlack
2026-05-14 1:05 ` sashiko-bot
2026-05-14 18:27 ` David Matlack
2026-05-12 18:48 ` [PATCH v5 04/11] PCI: liveupdate: Document driver binding responsibilities David Matlack
2026-05-12 18:48 ` [PATCH v5 05/11] PCI: liveupdate: Keep bus numbers constant during Live Update David Matlack
2026-05-14 1:36 ` sashiko-bot
2026-05-14 18:39 ` David Matlack
2026-05-22 17:59 ` Bjorn Helgaas
2026-05-12 18:48 ` [PATCH v5 06/11] PCI: liveupdate: Auto-preserve upstream bridges across " David Matlack
2026-05-14 2:05 ` sashiko-bot
2026-05-14 18:41 ` David Matlack
2026-05-12 18:48 ` [PATCH v5 07/11] PCI: liveupdate: Inherit ACS flags in incoming preserved devices David Matlack
2026-05-14 2:37 ` sashiko-bot
2026-05-14 18:46 ` David Matlack
2026-05-12 18:48 ` [PATCH v5 08/11] PCI: liveupdate: Inherit ARI Forwarding Enable on preserved bridges David Matlack
2026-05-12 18:48 ` [PATCH v5 09/11] PCI: liveupdate: Freeze preservation status during shutdown David Matlack
2026-05-14 3:14 ` sashiko-bot
2026-05-14 18:48 ` David Matlack
2026-05-12 18:48 ` [PATCH v5 10/11] PCI: liveupdate: Do not disable bus mastering on preserved devices during kexec David Matlack
2026-05-22 18:01 ` Bjorn Helgaas
2026-05-12 18:48 ` [PATCH v5 11/11] Documentation: PCI: Add documentation for Live Update David Matlack
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