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Date:   Mon, 9 May 2022 23:39:30 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Alex Williamson <alex.williamson@redhat.com>
Cc:     Bjorn Helgaas <helgaas@kernel.org>,
        Volodymyr Babchuk <Volodymyr_Babchuk@epam.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
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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);