[PATCH v2 0/4] VFIO platform reset
eric.auger at linaro.org
Fri Jun 5 08:06:28 PDT 2015
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
- 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
This series proposes to implement device specific reset functions in
separate vfio reset modules (in-kernel or external). The vfio-platform
driver holds a whitelist of implemented triplets (compat string, module
name, 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
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 | 98 ++++++++++++++++++++++
drivers/vfio/platform/vfio_platform_common.c | 75 ++++++++++++++++-
drivers/vfio/platform/vfio_platform_private.h | 14 ++++
7 files changed, 200 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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