From: Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: Christoph Hellwig <hch@infradead.org>,
Alex Williamson <alex.williamson@redhat.com>,
"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
Leon Romanovsky <leon@kernel.org>, Jason Gunthorpe <jgg@ziepe.ca>
Subject: Re: Write to srvio_numvfs triggers kernel panic
Date: Thu, 12 May 2022 07:18:30 +0000 [thread overview]
Message-ID: <877d6rkym2.fsf@epam.com> (raw)
In-Reply-To: <20220510173733.GA688834@bhelgaas>
Hello Bjorn,
Bjorn Helgaas <helgaas@kernel.org> writes:
> On Mon, May 09, 2022 at 11:39:30PM -0700, Christoph Hellwig wrote:
>> On Mon, May 09, 2022 at 10:58:57AM -0600, Alex Williamson wrote:
>> > is_physfn = 0, is_virtfn = 0: A non-SR-IOV function
>> > is_physfn = 1, is_virtfn = 0: An SR-IOV PF
>> > is_physfn = 0, is_virtfn = 1: An SR-IOV VF
>> >
>> > As implemented with bit fields this is 2 bits, which is more space
>> > efficient than an enum. Thanks,
>>
>> A two-bit bitfield with explicit constants for the values would probably
>> still much eaiser to understand.
>>
>> And there is some code that seems to intepret is_physfn a bit odd, e.g.:
>>
>> arch/powerpc/kernel/eeh_sysfs.c: np = pci_device_to_OF_node(pdev->is_physfn ? pdev : pdev->physfn);
>> arch/powerpc/kernel/eeh_sysfs.c: np = pci_device_to_OF_node(pdev->is_physfn ? pdev : pdev->physfn);
>
> "dev->sriov != NULL" and "dev->is_physfn" are basically the same and
> many of the dev->is_physfn uses in drivers/pci would end up being
> simpler if replaced with dev->sriov, e.g.,
>
> int pci_iov_virtfn_bus(struct pci_dev *dev, int vf_id)
> {
> if (!dev->is_physfn)
> return -EINVAL;
> return dev->bus->number + ((dev->devfn + dev->sriov->offset +
> dev->sriov->stride * vf_id) >> 8);
> }
>
> would be more obvious as:
>
> if (dev->sriov)
> return dev->bus->number + ((dev->devfn + dev->sriov->offset +
> dev->sriov->stride * vf_id) >> 8);
> return -EINVAL;
I'm not sure that this will work because dev->sriov and dev->physfn are
stored in the same union.
--
Volodymyr Babchuk at EPAM
prev parent reply other threads:[~2022-05-12 7:18 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-04 19:56 Write to srvio_numvfs triggers kernel panic Volodymyr Babchuk
2022-05-06 20:17 ` Bjorn Helgaas
2022-05-07 1:34 ` Jason Gunthorpe
2022-05-07 10:25 ` Volodymyr Babchuk
2022-05-08 11:19 ` Leon Romanovsky
2022-05-09 18:22 ` Keith Busch
2022-05-07 10:22 ` Volodymyr Babchuk
2022-05-07 15:41 ` Bjorn Helgaas
2022-05-08 11:07 ` Volodymyr Babchuk
2022-05-09 16:49 ` Bjorn Helgaas
2022-05-09 16:58 ` Alex Williamson
2022-05-10 6:39 ` Christoph Hellwig
2022-05-10 17:37 ` Bjorn Helgaas
2022-05-12 7:18 ` Volodymyr Babchuk [this message]
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