[RFC PATCH v7 0/3] PCI: Introduce a way to enforce all MMIO BARs not to share PAGE_SIZE

[Alexey Kardashevskiy]

On 15/11/16 13:53, Yongji Xie wrote:
> Hi Bjorn,
> 
> 
> Kindly ping. What do you think of the way to fix the bug that resources's
> size is changed
> 
> when using resource_alignment. Thanks.


Could anyone please comment on this? Thanks!



> 
> 
> On 2016/10/26 14:53, Yongji Xie wrote:
>> This series introduces a way for PCI resource allocator to force
>> MMIO 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.
>>
>> In our solution, we try to make use of the existing code path of
>> resource_alignment kernel parameter and add a macro to set default
>> alignment for it. Thus we can define this macro by default on some
>> archs which may easily hit the performance issue because of their
>> 64K page.
>>
>> In this series, patch 1,2 fixed bugs of using resource_alignment;
>> patch 3 adds a macro to set the default alignment of all MMIO BARs.
>>
>> Changelog v7:
>> - Rebased against v4.9-rc2
>> - Drop two merged patches
>> - Rework the patch which fix a bug that resources's size is changed when
>>    using resource_alignment
>> - Add a patch that fix a bug for IOV BARs when using resource_alignment
>>
>> Changelog v6:
>> - Remove the option "noresize@" of resource_alignment
>>
>> Changelog v5:
>> - Rebased against v4.8-rc6
>> - Drop the patch that forbidding disable memory decoding in
>>    pci_reassigndev_resource_alignment()
>>
>> Changelog v4:
>> - Rebased against v4.8-rc1
>> - Drop one irrelevant patch
>> - Drop the patch that adding wildcard to resource_alignment to enforce
>>    the alignment of all MMIO BARs to be at least PAGE_SIZE
>> - Change the format of option "noresize" of resource_alignment
>> - Code style improvements
>>
>> Changelog v3:
>> - Ignore enforced alignment to fixed BARs
>> - Fix issue that disabling memory decoding when reassigning the alignment
>> - Only enable default alignment on PowerNV platform
>>
>> Changelog v2:
>> - Ignore enforced alignment to VF BARs on
>> pci_reassigndev_resource_alignment()
>>
>> Yongji Xie (3):
>>    PCI: Ignore requested alignment for IOV BARs
>>    PCI: Restore resource's size if we expand it by using resource_alignment
>>    PCI: Add a macro to set default alignment for all PCI devices
>>
>>   arch/powerpc/include/asm/pci.h |    4 ++++
>>   drivers/pci/pci.c              |    6 +++++-
>>   drivers/pci/setup-bus.c        |   19 +++++++++++++++++++
>>   include/linux/pci.h            |    1 +
>>   4 files changed, 29 insertions(+), 1 deletion(-)
>>
> 


-- 
Alexey