linux-kernel - [PATCH v3 0/3] Allow custom PCI resource alignment on pseries

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Date:   Mon, 27 May 2019 23:03:10 -0500
From:   Shawn Anastasio <shawn@...stas.io>
To:     linux-pci@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Cc:     bhelgaas@...gle.com, benh@...nel.crashing.org, paulus@...ba.org,
        mpe@...erman.id.au, sbobroff@...ux.ibm.com,
        xyjxie@...ux.vnet.ibm.com, rppt@...ux.ibm.com,
        linux-kernel@...r.kernel.org
Subject: [PATCH v3 0/3] Allow custom PCI resource alignment on pseries

Changes from v2 to v3:
  - Fix wrong return type of ppc pcibios_ignore_alignment_request
    (Not sure how my local compile didn't catch that!)

Hello all,

This patch set implements support for user-specified PCI resource
alignment on the pseries platform for hotplugged PCI devices.
Currently on pseries, PCI resource alignments specified with the
pci=resource_alignment commandline argument are ignored, since
the firmware is in charge of managing the PCI resources. In the
case of hotplugged devices, though, the kernel is in charge of 
configuring the resources and should obey alignment requirements.

The current behavior of ignoring the alignment for hotplugged devices
results in sub-page BARs landing between page boundaries and
becoming un-mappable from userspace via the VFIO framework.
This issue was observed on a pseries KVM guest with hotplugged
ivshmem devices.

With these changes, users can specify an appropriate
pci=resource_alignment argument on boot for devices they wish to use 
with VFIO.

In the future, this could be extended to provide page-aligned
resources by default for hotplugged devices, similar to what is done
on powernv by commit 382746376993 ("powerpc/powernv: Override
pcibios_default_alignment() to force PCI devices to be page aligned").

Feedback is appreciated.

Thanks,
Shawn

Shawn Anastasio (3):
  PCI: Introduce pcibios_ignore_alignment_request
  powerpc/64: Enable pcibios_after_init hook on ppc64
  powerpc/pseries: Allow user-specified PCI resource alignment after
    init

 arch/powerpc/include/asm/machdep.h     |  6 ++++--
 arch/powerpc/kernel/pci-common.c       |  9 +++++++++
 arch/powerpc/kernel/pci_64.c           |  4 ++++
 arch/powerpc/platforms/pseries/setup.c | 22 ++++++++++++++++++++++
 drivers/pci/pci.c                      |  9 +++++++--
 include/linux/pci.h                    |  1 +
 6 files changed, 47 insertions(+), 4 deletions(-)

-- 
2.20.1