On Thu, 2020-01-30 at 15:26 -0600, Bjorn Helgaas wrote:
> On Wed, Jan 29, 2020 at 06:29:20PM +0300, Sergei Miroshnichenko
> wrote:
> > When movable BARs are enabled, and if a bridge contains a device
> > with fixed
> > (IORESOURCE_PCI_FIXED) or immovable BARs, the corresponding windows
> > can't
>
> What is the difference between fixed (IORESOURCE_PCI_FIXED) and
> immovable BARs? I'm hesitant to add a new concept ("immovable") with
> a different name but very similar meaning.
>
> I understand that in the case of bridge windows, you may need to
> track
> only part of the window, as opposed to a BAR where the entire BAR has
> to be either fixed or movable, but I think adding a new term will be
> confusing.
>
I thought the term "fixed BAR" has some legacy scent, and those marked
with flag IORESOURCE_PCI_FIXED are fixed forever. But a BAR may become
movable after rmmod-ing its driver that didn't support movable BARs.
Still, the IORESOURCE_PCI_FIXED is used just a few times in the kernel,
so the "fixed BAR" term is probably not so well-established, so I don't
mind referring all non-movables as "fixed": both marked with the flag
and not. Will change all of them in v8.
> > be moved too far away from their original positions - they must
> > still
> > contain all the fixed/immovable BARs, like that:
> >
> > 1) Window position before a bus rescan:
> >
> > | <-- root bridge
> > window --> |
> > |
> > |
> > | | <-- bridge window -->
> > | |
> > | | movable BARs | **fixed BAR**
> > | |
> > ^^^^^^^^^^^^
> >
> > 2) Possible valid outcome after rescan and move:
> >
> > | <-- root bridge
> > window --> |
> > |
> > |
> > | | <-- bridge window -->
> > | |
> > | | **fixed BAR** | Movable BARs
> > | |
> > ^^^^^^^^^^^^
> >
> > An immovable area of a bridge window is a range that covers all the
> > fixed
> > and immovable BARs of direct children, and all the fixed area of
> > children
> > bridges:
> >
> > | <-- root bridge
> > window --> |
> > |
> > |
> > | | <-- bridge window level 1 -
> > -> | |
> > | | ******************** immovable area
> > ******************* | |
> > | |
> > | |
> > | | **fixed BAR** | <-- bridge window level 2 --> |
> > BARs | |
> > | | | *********** immovable area ***********
> > | | |
> > | | | |
> > | |
> > | | | **fixed BAR** | BARs | **fixed BAR**
> > | | |
> > ^^^^
> >
> > To store these areas, the .immovable_range field has been added to
> > struct
> > pci_bus for every bridge window type: IO, MEM and PREFETCH. It is
> > filled
> > recursively from leaves to the root before a rescan.
> >
> > Signed-off-by: Sergei Miroshnichenko <s.miroshnichenko@xxxxxxxxx>
> > ---
> > drivers/pci/pci.h | 14 ++++++++
> > drivers/pci/probe.c | 88
> > +++++++++++++++++++++++++++++++++++++++++++++
> > include/linux/pci.h | 6 ++++
> > 3 files changed, 108 insertions(+)
> >
> > diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> > index 3b4c982772d3..5f2051c8531c 100644
> > --- a/drivers/pci/pci.h
> > +++ b/drivers/pci/pci.h
> > @@ -404,6 +404,20 @@ static inline bool
> > pci_dev_is_disconnected(const struct pci_dev *dev)
> > return dev->error_state == pci_channel_io_perm_failure;
> > }
> >
> > +static inline int pci_get_bridge_resource_idx(struct resource *r)
> > +{
> > + int idx = 1;
> > +
> > + if (r->flags & IORESOURCE_IO)
> > + idx = 0;
> > + else if (!(r->flags & IORESOURCE_PREFETCH))
> > + idx = 1;
> > + else if (r->flags & IORESOURCE_MEM_64)
> > + idx = 2;
>
> Random nit: No variables or elses required:
>
> if (r->flags & IORESOURCE_IO)
> return 0;
> if (!(r->flags & IORESOURCE_PREFETCH))
> return 1;
> ...
>
Thank you!
Best regards,
Serge
> > + return idx;
> > +}
