[PATCH v2 0/4] PCI: Add support for enforcing all MMIO BARs not to share PAGE_SIZE

From: Yongji Xie
Date: Mon May 30 2016 - 09:04:51 EST

This series aims to add an option for PCI resource allocator to
force BARs not to share PAGE_SIZE. This would make sense to VFIO
driver. Because current VFIO implementation disallows to mmap
sub-page(size < PAGE_SIZE) MMIO BARs which may share the same page
with other BARs for security reasons. Thus, we have to handle mmio
access to these BARs in QEMU emulation rather than in guest which
will cause some performance loss.

To achieve that, we would like to make use of the existing
resource_alignment kernel parameter and force a minimum alignment
of PAGE_SIZE. It's flexible. And we can default to enable it on
some archs which may easily hit the performance issue because of
their 64K page.

In this series, patch 1 fixed a bug of resource_alignment; patch 2,3
tried to add a new option for resource_alignment to use
IORESOURCE_STARTALIGN to specify the alignment of PCI BARs; patch 4
modified resource_alignment to support syntax which can be used to
enforce the alignment of all MMIO BARs to be at least PAGE_SIZE.

Changelog v2:
- Ignore enforced alignment to VF BARs on pci_reassigndev_resource_alignment()

Yongji Xie (4):
PCI: Ignore resource_alignment if PCI_PROBE_ONLY was set
PCI: Do not Use IORESOURCE_STARTALIGN to identify bridge resources
PCI: Add a new option for resource_alignment to reassign alignment
PCI: Add support for enforcing all MMIO BARs to be page aligned

Documentation/kernel-parameters.txt | 7 ++-
arch/powerpc/include/asm/pci.h | 2 +
drivers/pci/pci.c | 109 ++++++++++++++++++++++++++++-------
drivers/pci/setup-bus.c | 9 ++-
4 files changed, 102 insertions(+), 25 deletions(-)