linux-kernel - Re: [PATCH v2 01/10] PCI/LUO: Register with Liveupdate Orchestrator

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Message-ID: <2025093014-qualify-scoop-c406@gregkh>
Date: Tue, 30 Sep 2025 17:17:10 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Chris Li <chrisl@...nel.org>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Danilo Krummrich <dakr@...nel.org>, Len Brown <lenb@...nel.org>,
	Pasha Tatashin <pasha.tatashin@...een.com>,
	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>,
	Jason Miu <jasonmiu@...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>
Subject: Re: [PATCH v2 01/10] PCI/LUO: Register with Liveupdate Orchestrator

On Tue, Sep 16, 2025 at 12:45:09AM -0700, Chris Li wrote:
> Register PCI subsystem with the Liveupdate Orchestrator
> and provide noop liveupdate callbacks.
> 
> Signed-off-by: Chris Li <chrisl@...nel.org>
> ---
>  MAINTAINERS              |  2 ++
>  drivers/pci/Makefile     |  1 +
>  drivers/pci/liveupdate.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 57 insertions(+)
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 91cec3288cc81aea199f730924eee1f5fda1fd72..85749a5da69f88544ccc749e9d723b1b54c0e3b7 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -14014,11 +14014,13 @@ F:	tools/testing/selftests/livepatch/
>  
>  LIVE UPDATE
>  M:	Pasha Tatashin <pasha.tatashin@...een.com>
> +M:	Chris Li <chrisl@...nel.org>
>  L:	linux-kernel@...r.kernel.org
>  S:	Maintained
>  F:	Documentation/ABI/testing/sysfs-kernel-liveupdate
>  F:	Documentation/admin-guide/liveupdate.rst
>  F:	drivers/misc/liveupdate/
> +F:	drivers/pci/liveupdate/
>  F:	include/linux/liveupdate.h
>  F:	include/uapi/linux/liveupdate.h
>  F:	tools/testing/selftests/liveupdate/
> diff --git a/drivers/pci/Makefile b/drivers/pci/Makefile
> index 67647f1880fb8fb0629d680398f5b88d69aac660..aa1bac7aed7d12c641a6b55e56176fb3cdde4c91 100644
> --- a/drivers/pci/Makefile
> +++ b/drivers/pci/Makefile
> @@ -37,6 +37,7 @@ obj-$(CONFIG_PCI_DOE)		+= doe.o
>  obj-$(CONFIG_PCI_DYNAMIC_OF_NODES) += of_property.o
>  obj-$(CONFIG_PCI_NPEM)		+= npem.o
>  obj-$(CONFIG_PCIE_TPH)		+= tph.o
> +obj-$(CONFIG_LIVEUPDATE)	+= liveupdate.o
>  
>  # Endpoint library must be initialized before its users
>  obj-$(CONFIG_PCI_ENDPOINT)	+= endpoint/
> diff --git a/drivers/pci/liveupdate.c b/drivers/pci/liveupdate.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..86b4f3a2fb44781c6e323ba029db510450556fa9
> --- /dev/null
> +++ b/drivers/pci/liveupdate.c
> @@ -0,0 +1,54 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +/*
> + * Copyright (c) 2025, Google LLC.
> + * Chris Li <chrisl@...nel.org>
> + */
> +
> +#define pr_fmt(fmt) "PCI liveupdate: " fmt
> +
> +#include <linux/liveupdate.h>
> +
> +#define PCI_SUBSYSTEM_NAME "pci"
> +
> +static int pci_liveupdate_prepare(void *arg, u64 *data)
> +{
> +	pr_info("prepare data[%llx]\n", *data);
> +	return 0;
> +}
> +
> +static int pci_liveupdate_freeze(void *arg, u64 *data)
> +{
> +	pr_info("freeze data[%llx]\n", *data);
> +	return 0;
> +}
> +
> +static void pci_liveupdate_cancel(void *arg, u64 data)
> +{
> +	pr_info("cancel data[%llx]\n", data);
> +}
> +
> +static void pci_liveupdate_finish(void *arg, u64 data)
> +{
> +	pr_info("finish data[%llx]\n", data);
> +}
> +
> +struct liveupdate_subsystem pci_liveupdate_ops = {
> +	.prepare = pci_liveupdate_prepare,
> +	.freeze = pci_liveupdate_freeze,
> +	.cancel = pci_liveupdate_cancel,
> +	.finish = pci_liveupdate_finish,
> +	.name = PCI_SUBSYSTEM_NAME,
> +};
> +
> +static int __init pci_liveupdate_init(void)
> +{
> +	int ret;
> +
> +	ret = liveupdate_register_subsystem(&pci_liveupdate_ops);
> +	if (ret && liveupdate_state_updated())
> +		panic("PCI liveupdate: Register subsystem failed: %d", ret);
> +	WARN(ret, "PCI liveupdate: Register subsystem failed %d", ret);

But this didn't fail.

And you just crashed the box if panic-on-warn is enabled, so if some
test infrastructure builds this first patch, boom.

{sigh}

If you are going to do a "dummy" driver, please make it at least work
and not do anything bad.

thanks,

greg k-h