On Fri, Feb 05, 2021 at 02:36:32PM +0100, Daniel Vetter 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@xxxxxxxxx>
Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
I wish we weren't extending a known-racy mechanism to do this, but at
least we're not *adding* a brand new race.
> Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
> Cc: Jason Gunthorpe <jgg@xxxxxxxx>
> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: John Hubbard <jhubbard@xxxxxxxxxx>
> Cc: Jérôme Glisse <jglisse@xxxxxxxxxx>
> Cc: Jan Kara <jack@xxxxxxx>
> Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Cc: linux-mm@xxxxxxxxx
> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> Cc: linux-samsung-soc@xxxxxxxxxxxxxxx
> Cc: linux-media@xxxxxxxxxxxxxxx
> Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> Cc: linux-pci@xxxxxxxxxxxxxxx
> ---
> 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
>
>
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