[PATCH] PCI: Also set up legacy files only after sysfs init

[Daniel Vetter]

Hi Bjorn,

Can you ack this for merging through my topic branch with the other
follow_pfn/iomem revoke fixes for 5.12?

If not, what's the plan for getting this (or equivalent functionality)
in for 5.13? I have more of these follow_pfn/iomem revoke patches on
top, so I'd like to get the first cut merged sooner than later if
possible. And the other prep work has been in -next since -rc1.

Thanks, Daniel

On Fri, Feb 5, 2021 at 2:36 PM Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
>
> We are already doing this for all the regular sysfs files on PCI
> devices, but not yet on the legacy io files on the PCI buses. Thus far
> no problem, but in the next patch I want to wire up iomem revoke
> support. That needs the vfs up and running already to make sure that
> iomem_get_mapping() works.
>
> Wire it up exactly like the existing code in
> pci_create_sysfs_dev_files(). Note that pci_remove_legacy_files()
> doesn't need a check since the one for pci_bus->legacy_io is
> sufficient.
>
> An alternative solution would be to implement a callback in sysfs to
> set up the address space from iomem_get_mapping() when userspace calls
> mmap(). This also works, but Greg didn't really like that just to work
> around an ordering issue when the kernel loads initially.
>
> v2: Improve commit message (Bjorn)
>
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
> Cc: Stephen Rothwell <sfr at canb.auug.org.au>
> Cc: Jason Gunthorpe <jgg at ziepe.ca>
> Cc: Kees Cook <keescook at chromium.org>
> Cc: Dan Williams <dan.j.williams at intel.com>
> Cc: Andrew Morton <akpm at linux-foundation.org>
> Cc: John Hubbard <jhubbard at nvidia.com>
> Cc: Jérôme Glisse <jglisse at redhat.com>
> Cc: Jan Kara <jack at suse.cz>
> Cc: Dan Williams <dan.j.williams at intel.com>
> Cc: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
> Cc: linux-mm at kvack.org
> Cc: linux-arm-kernel at lists.infradead.org
> Cc: linux-samsung-soc at vger.kernel.org
> Cc: linux-media at vger.kernel.org
> Cc: Bjorn Helgaas <bhelgaas at google.com>
> Cc: linux-pci at vger.kernel.org
> ---
>  drivers/pci/pci-sysfs.c | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index fb072f4b3176..0c45b4f7b214 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -927,6 +927,9 @@ void pci_create_legacy_files(struct pci_bus *b)
>  {
>         int error;
>
> +       if (!sysfs_initialized)
> +               return;
> +
>         b->legacy_io = kcalloc(2, sizeof(struct bin_attribute),
>                                GFP_ATOMIC);
>         if (!b->legacy_io)
> @@ -1448,6 +1451,7 @@ void pci_remove_sysfs_dev_files(struct pci_dev *pdev)
>  static int __init pci_sysfs_init(void)
>  {
>         struct pci_dev *pdev = NULL;
> +       struct pci_bus *pbus = NULL;
>         int retval;
>
>         sysfs_initialized = 1;
> @@ -1459,6 +1463,9 @@ static int __init pci_sysfs_init(void)
>                 }
>         }
>
> +       while ((pbus = pci_find_next_bus(pbus)))
> +               pci_create_legacy_files(pbus);
> +
>         return 0;
>  }
>  late_initcall(pci_sysfs_init);
> --
> 2.30.0
>


-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch