Re: [PATCH v4 0/4] VFIO platform reset

[Baptiste Reynal]

Hello everyone,

I tested and reviewed the patches, everything's fine for me.

I agree to be maintainer of vfio platform drivers, though I don't
think the volume of patches about VFIO will justify a new mailing
list.

Regards,
Baptiste

On Thu, Jun 18, 2015 at 12:31 AM, Alex Williamson
<alex.williamson@xxxxxxxxxx> wrote:
> On Mon, 2015-06-15 at 11:09 +0200, Eric Auger wrote:
>> In situations where the userspace driver is stopped abnormally and the
>> VFIO platform device is released, the assigned HW device currently is
>> left running. As a consequence the HW device might continue issuing IRQs
>> and performing DMA accesses.
>>
>> On release, no physical IRQ handler is setup anymore. Also the DMA buffers
>> are unmapped leading to IOMMU aborts. So there is no serious consequence.
>>
>> However when assigning that HW device again to another userspace driver,
>> this latter might face some unexpected IRQs and DMA accesses, which are
>> the result of the previous assignment.
>>
>> In virtualization use-case, a VM newly granted with that HW device may be
>> impacted by the assignment of that device to a previous VM:
>> - IRQs may be injected very early when booting the new guest, even before
>>   the guest driver has initialized leading to possible driver state
>>   inconsistency.
>> - DMA accesses may hit the newly mapped VM address space at addresses that
>>   may jeopardize the integrity of the newly installed VM.
>>
>> Obviously the criticity depends on the assigned HW device.
>>
>> As opposed to PCI, there is no standard mechanism to reset the platform
>> device.
>>
>> This series proposes to implement device specific reset functions in
>> separate in-kernel vfio reset modules. The vfio-platform driver holds
>> a whitelist of implemented triplets (compat string, module name,
>> reset function name). When the vfio-platform driver is probed it identifies
>> the fellow reset module/function matching the compat string of the
>> device, if any, and forces the load of this reset module.
>>
>> A first reset module is provided: the vfio-platform-calxedaxgmac
>> module which implements a basic reset for the Calxeda xgmac.
>>
>> The series can be found at
>> https://git.linaro.org/people/eric.auger/linux.git/shortlog/refs/heads/v4.1-rc8-reset-v4
>>
>> History:
>> v3 -> v4:
>> - fix the commit message of "VFIO: platform: add reset struct and lookup table"
>
> Baptiste,
>
> Any comments?  Should we also add something like this to MAINTAINERS
> before we go much further?
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index d8afd29..c6bf7f6 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -10545,6 +10545,12 @@ F:     drivers/vfio/
>  F:     include/linux/vfio.h
>  F:     include/uapi/linux/vfio.h
>
> +VFIO PLATFORM DRIVER
> +M:     Baptiste Reynal <b.reynal@xxxxxxxxxxxxxxxxxxxxxx>
> +L:     kvm@xxxxxxxxxxxxxxx
> +S:     Maintained
> +F:     drivers/vfio/platform/
> +
>  VIDEOBUF2 FRAMEWORK
>  M:     Pawel Osciak <pawel@xxxxxxxxxx>
>  M:     Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
>
> I'm not sure what you want to be the primary list, maybe it's time to
> ask for a vfio list.  Thanks,
> Alex
>
>>
>> v2 -> v3:
>> - remove void module_init/exit functions in calxeda reset module
>> - remove enum vfio_platform_reset_type
>> - for reset lookup, use ARRAY_SIZE
>> - in reset put use symbol_put_addr
>>
>> v1 -> v2:
>> - much simplified compared to v1 although principle of external modules is
>>   kept: removed mechanism of dynamic registration of reset functions
>> - list is replaced by whitelist lookup table
>> - name of the reset function also stored in the lookup table
>> - autoload of reset modules
>>
>> RFC -> PATCH v1:
>> - solution now based on a lookup list instead of specialized driver
>>
>>
>> Eric Auger (4):
>>   VFIO: platform: add reset struct and lookup table
>>   VFIO: platform: add reset callback
>>   VFIO: platform: populate the reset function on probe
>>   VFIO: platform: Calxeda xgmac reset module
>>
>>  drivers/vfio/platform/Kconfig                      |  2 +
>>  drivers/vfio/platform/Makefile                     |  2 +
>>  drivers/vfio/platform/reset/Kconfig                |  7 ++
>>  drivers/vfio/platform/reset/Makefile               |  5 ++
>>  .../platform/reset/vfio_platform_calxedaxgmac.c    | 86 ++++++++++++++++++++++
>>  drivers/vfio/platform/vfio_platform_common.c       | 60 ++++++++++++++-
>>  drivers/vfio/platform/vfio_platform_private.h      |  7 ++
>>  7 files changed, 166 insertions(+), 3 deletions(-)
>>  create mode 100644 drivers/vfio/platform/reset/Kconfig
>>  create mode 100644 drivers/vfio/platform/reset/Makefile
>>  create mode 100644 drivers/vfio/platform/reset/vfio_platform_calxedaxgmac.c
>>
>
>
>
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