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

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Message-ID: <55DF0AFD.7020806@linaro.org>
Date:	Thu, 27 Aug 2015 15:05:01 +0200
From:	Eric Auger <eric.auger@...aro.org>
To:	eric.auger@...com, linux-arm-kernel@...ts.infradead.org,
	b.reynal@...tualopensystems.com, alex.williamson@...hat.com
CC:	linux-kernel@...r.kernel.org, patches@...aro.org,
	christoffer.dall@...aro.org
Subject: Re: [PATCH v4 0/4] VFIO platform reset

Dear all,

Please ignore this email. It is a reply to a wrong thread (was targeting
[PATCH v4 0/4] irqchip: GICv2/v3: Add support for irq_vcpu_affinity).

My apologies

Best Regards

Eric

On 08/27/2015 01:56 PM, Eric Auger wrote:
> Hi Marc,
> 
> I tested the series on Calxeda Midway with VFIO use case. Also reviewed
> it again without finding anything new.
> 
> Tested-by: Eric Auger <eric.auger@...aro.org>
> Reviewed-by: Eric Auger <eric.auger@...aro.org>
> 
> Best Regards
> 
> Eric
> 
> On 06/15/2015 11:09 AM, 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"
>>
>> 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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