linux-kernel - Re: [PATCH 1/4] PCI/pwrctrl: Move creation of pwrctrl devices to pci_scan

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Z2F5Oph2o8o_LiZc@wunner.de>
Date: Tue, 17 Dec 2024 14:14:34 +0100
From: Lukas Wunner <lukas@...ner.de>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
	Bartosz Golaszewski <brgl@...ev.pl>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konradybcio@...nel.org>,
	Qiang Yu <quic_qianyu@...cinc.com>
Subject: Re: [PATCH 1/4] PCI/pwrctrl: Move creation of pwrctrl devices to
 pci_scan_device()

On Mon, Dec 16, 2024 at 10:45:21AM +0530, Manivannan Sadhasivam wrote:
> On Sun, Dec 15, 2024 at 06:19:22PM +0100, Lukas Wunner wrote:
> > On Tue, Dec 10, 2024 at 03:25:24PM +0530, Manivannan Sadhasivam wrote:
> > > diff --git a/drivers/pci/pwrctrl/core.c b/drivers/pci/pwrctrl/core.c
> > > index 2fb174db91e5..9cc7e2b7f2b5 100644
> > > --- a/drivers/pci/pwrctrl/core.c
> > > +++ b/drivers/pci/pwrctrl/core.c
> > > @@ -44,7 +44,7 @@ static void rescan_work_func(struct work_struct *work)
> > >  						   struct pci_pwrctrl, work);
> > >  
> > >  	pci_lock_rescan_remove();
> > > -	pci_rescan_bus(to_pci_dev(pwrctrl->dev->parent)->bus);
> > > +	pci_rescan_bus(to_pci_host_bridge(pwrctrl->dev->parent)->bus);
> > >  	pci_unlock_rescan_remove();
> > >  }
> > 
> > Remind me, what's the purpose of this?  I'm guessing that it
> > recursively creates the platform devices below the newly
> > powered up device, is that correct?  If so, is it still
> > necessary?  Doesn't the new approach automatically create
> > those devices upon their enumeration?
> 
> If the pwrctrl driver is available at the time of platform device creation,
> this is not needed. But if the driver is not available at that time and
> probed later, then we need to rescan the bus to enumerate the devices.

I see.  Sounds like this can be made conditional on the caller
being a module.  I think you could achieve this with the following
in pci_pwrctl_device_set_ready():

-	schedule_work(&pwrctl->work);
+	if (is_module_address(_RET_IP_))
+		schedule_work(&pwrctl->work);

Though you'd also have to declare pci_pwrctl_device_set_ready()
"__attribute__((always_inline))" so that it gets inlined into
devm_pci_pwrctl_device_set_ready() and the condition works there
as well.

I'm wondering whether the bus notifier is still necessary with
the new scheme.  Since the power control device is instantiated
and destroyed in unison with the pci_dev, can't the device link
always be created on instantiation of the power control device?

Thanks,

Lukas