Re: [PATCH] PCI: Equalize hotplug memory for non/occupied slots

["Derrick, Jonathan" <jonathan.derrick@intel.com>]

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On Tue, 2018-08-14 at 13:16 -0500, Bjorn Helgaas wrote:
> On Wed, Jul 25, 2018 at 05:02:59PM -0600, Jon Derrick wrote:
> > Currently, a hotplug bridge will be given hpmemsize additional
> > memory if
> > available, in order to satisfy any future hotplug allocation
> > requirements.
> > 
> > These calculations don't consider the current memory size of the
> > hotplug
> > bridge/slot, so hotplug bridges/slots which have downstream devices
> > will
> > get their current allocation in addition to the hpmemsize value.
> > 
> > This makes for possibly undesirable results with a mix of
> > unoccupied and
> > occupied slots (ex, with hpmemsize=2M):
> > 
> > 02:03.0 PCI bridge: <-- Occupied
> > 	Memory behind bridge: d6200000-d64fffff [size=3M]
> > 02:04.0 PCI bridge: <-- Unoccupied
> > 	Memory behind bridge: d6500000-d66fffff [size=2M]
> > 
> > This change considers the current allocation size when using the
> > hpmemsize parameter to make the reservations predictable for the
> > mix of
> > unoccupied and occupied slots:
> > 
> > 02:03.0 PCI bridge: <-- Occupied
> > 	Memory behind bridge: d6200000-d63fffff [size=2M]
> > 02:04.0 PCI bridge: <-- Unoccupied
> > 	Memory behind bridge: d6400000-d65fffff [size=2M]
> 
> The I/O sizing code (pbus_size_io() and calculate_iosize()) is
> essentially
> identical to the mem sizing code you're updating.  I assume the same
> considerations would apply there?  If not, please include a note in
> the
> changelog about why you changed the mem code but not the I/O code.
> 

Thanks for the look Bjorn.
I'll follow-up with v2 set with an I/O patch in a few days

[snip]

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