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    SubjectRe: [PATCH v4 0/4] VFIO platform reset
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    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@virtualopensystems.com>
    +L: kvm@vger.kernel.org
    +S: Maintained
    +F: drivers/vfio/platform/
    +
    VIDEOBUF2 FRAMEWORK
    M: Pawel Osciak <pawel@osciak.com>
    M: Marek Szyprowski <m.szyprowski@samsung.com>
    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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