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From: Amey Narkhede <ameynarkhede03@gmail.com>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: alex.williamson@redhat.com,
	Raphael Norwitz <raphael.norwitz@nutanix.com>,
	linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
	kw@linux.com, Shanker Donthineni <sdonthineni@nvidia.com>,
	Sinan Kaya <okaya@kernel.org>, Len Brown <lenb@kernel.org>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>
Subject: Re: [PATCH v10 4/8] PCI/sysfs: Allow userspace to query and set device reset mechanism
Date: Thu, 29 Jul 2021 00:28:31 +0530	[thread overview]
Message-ID: <20210728185831.isdqa5t5oxxjfhnv@archlinux> (raw)
In-Reply-To: <20210728181333.GA836307@bjorn-Precision-5520>

On 21/07/28 01:13PM, Bjorn Helgaas wrote:
> On Wed, Jul 28, 2021 at 11:29:50PM +0530, Amey Narkhede wrote:
> > On 21/07/27 06:28PM, Bjorn Helgaas wrote:
> > > On Fri, Jul 09, 2021 at 06:08:09PM +0530, Amey Narkhede wrote:
> > > > Add reset_method sysfs attribute to enable user to query and set user
> > > > preferred device reset methods and their ordering.
> > > >
> > > > Co-developed-by: Alex Williamson <alex.williamson@redhat.com>
> > > > Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> > > > Signed-off-by: Amey Narkhede <ameynarkhede03@gmail.com>
> > > > ---
> > > >  Documentation/ABI/testing/sysfs-bus-pci |  19 +++++
> > > >  drivers/pci/pci-sysfs.c                 | 103 ++++++++++++++++++++++++
> > > >  2 files changed, 122 insertions(+)
> > > >
> > > > diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
> > > > index ef00fada2..43f4e33c7 100644
> > > > --- a/Documentation/ABI/testing/sysfs-bus-pci
> > > > +++ b/Documentation/ABI/testing/sysfs-bus-pci
> > > > @@ -121,6 +121,25 @@ Description:
> > > >  		child buses, and re-discover devices removed earlier
> > > >  		from this part of the device tree.
> > > >
> > > > +What:		/sys/bus/pci/devices/.../reset_method
> > > > +Date:		March 2021
> > > > +Contact:	Amey Narkhede <ameynarkhede03@gmail.com>
> > > > +Description:
> > > > +		Some devices allow an individual function to be reset
> > > > +		without affecting other functions in the same slot.
> > > > +
> > > > +		For devices that have this support, a file named
> > > > +		reset_method will be present in sysfs. Initially reading
> > > > +		this file will give names of the device supported reset
> > > > +		methods and their ordering. After write, this file will
> > > > +		give names and ordering of currently enabled reset methods.
> > > > +		Writing the name or comma separated list of names of any of
> > > > +		the device supported reset methods to this file will set
> > > > +		the reset methods and their ordering to be used when
> > > > +		resetting the device. Writing empty string to this file
> > > > +		will disable ability to reset the device and writing
> > > > +		"default" will return to the original value.
> > > > +
> > > >  What:		/sys/bus/pci/devices/.../reset
> > > >  Date:		July 2009
> > > >  Contact:	Michael S. Tsirkin <mst@redhat.com>
> > >
> > [...]
> >
> > > > +		int i;
> > > > +
> > > > +		if (sysfs_streq(name, ""))
> > > > +			continue;
> > > > +
> > > > +		name = strim(name);
> > > > +
> > > > +		for (i = 1; i < PCI_NUM_RESET_METHODS; i++) {
> > > > +			if (sysfs_streq(name, pci_reset_fn_methods[i].name) &&
> > > > +			    !pci_reset_fn_methods[i].reset_fn(pdev, 1)) {
> > > > +				reset_methods[n++] = i;
> > >
> > > Can we build this directly in pdev->reset_methods[] so we don't need
> > > the memcpy() below?
> > >
> > This is to avoid writing partial values directly to dev->reset_methods.
> > So for example if user writes flr,unsupported_value then
> > dev->reset_methods should not be modified even though flr is valid reset
> > method in this example to avoid partial writes. Either operation(in this
> > case writing supported reset methods to reset_method attr) succeeds
> > completely or it fails othewise.
>
> I guess the question is, if somebody writes
>
>   flr junk bus
>
> and we set the supported methods to "flr bus", is that OK?  It seems
> OK to me; obviously we have to protect ourselves from attack, but
> over-zealous checking can make things unnecessarily complicated.
The problem is once we encounter "junk" we return -EINVAL so in your
example we only set flr.

Thanks,
Amey

  reply	other threads:[~2021-07-28 18:58 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-09 12:38 [PATCH v10 0/8] Expose and manage PCI device reset Amey Narkhede
2021-07-09 12:38 ` [PATCH v10 1/8] PCI: Add pcie_reset_flr to follow calling convention of other reset methods Amey Narkhede
2021-07-12 22:07   ` Alex Williamson
2021-07-27 22:12   ` Bjorn Helgaas
2021-07-28 18:54     ` Shanker R Donthineni
2021-07-28 20:23       ` Bjorn Helgaas
2021-07-28 21:58         ` Shanker R Donthineni
2021-07-28 22:04           ` Shanker R Donthineni
2021-07-28 22:16           ` Bjorn Helgaas
2021-07-09 12:38 ` [PATCH v10 2/8] PCI: Add new array for keeping track of ordering of " Amey Narkhede
2021-07-27 22:59   ` Bjorn Helgaas
2021-07-28 17:45     ` Amey Narkhede
2021-07-28 17:59       ` Bjorn Helgaas
2021-07-28 18:17         ` Shanker R Donthineni
2021-07-28 18:08       ` Shanker R Donthineni
2021-07-28 18:31     ` Shanker R Donthineni
2021-07-28 20:25       ` Bjorn Helgaas
2021-07-28 22:01         ` Shanker R Donthineni
2021-07-09 12:38 ` [PATCH v10 3/8] PCI: Remove reset_fn field from pci_dev Amey Narkhede
2021-07-09 12:38 ` [PATCH v10 4/8] PCI/sysfs: Allow userspace to query and set device reset mechanism Amey Narkhede
2021-07-27 23:28   ` Bjorn Helgaas
2021-07-28  1:27     ` Krzysztof Wilczyński
2021-07-28 15:36       ` Bjorn Helgaas
2021-07-28 17:59     ` Amey Narkhede
2021-07-28 18:13       ` Bjorn Helgaas
2021-07-28 18:58         ` Amey Narkhede [this message]
2021-07-28 20:18           ` Bjorn Helgaas
2021-07-31 19:15     ` Amey Narkhede
2021-07-28 17:09   ` Bjorn Helgaas
2021-07-09 12:38 ` [PATCH v10 5/8] PCI: Define a function to set ACPI_COMPANION in pci_dev Amey Narkhede
2021-07-12 22:29   ` Alex Williamson
2021-07-09 12:38 ` [PATCH v10 6/8] PCI: Setup ACPI fwnode early and at the same time with OF Amey Narkhede
2021-07-12 23:09   ` Alex Williamson
2021-07-27 23:30   ` Bjorn Helgaas
2021-07-27 23:50     ` Shanker R Donthineni
2021-07-09 12:38 ` [PATCH v10 7/8] PCI: Add support for ACPI _RST reset method Amey Narkhede
2021-07-12 23:09   ` Alex Williamson
2021-07-13  0:51     ` Shanker R Donthineni
2021-07-14 22:56       ` Alex Williamson
2021-07-09 12:38 ` [PATCH v10 8/8] PCI: Change the type of probe argument in reset functions Amey Narkhede
2021-07-12 22:24   ` Alex Williamson
2021-07-27 22:22   ` Bjorn Helgaas
2021-07-28 17:35     ` Amey Narkhede
2021-07-28 17:55       ` Bjorn Helgaas
2021-07-09 12:46 ` [PATCH v10 0/8] Expose and manage PCI device reset Amey Narkhede

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