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docs/devel/reset: Document reset expectations for DMA and IOMMU

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To avoid any translation faults, the IOMMUs are expected to be
reset after the devices they protect. Document that we expect
DMA requests to be stopped during the 'enter' or 'hold' phase
while IOMMUs should be reset during the 'exit' phase.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Message-Id: <20250218182737.76722-6-eric.auger@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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Eric Auger 2025-02-18 19:25:35 +01:00 committed by Michael S. Tsirkin
parent d410e70952
commit dd6d545e8f
1 changed files with 5 additions and 0 deletions
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docs/devel/reset.rst
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@ -143,6 +143,11 @@ The *exit* phase is executed only when the last reset operation ends. Therefore
the object does not need to care how many of reset controllers it has and how
many of them have started a reset.
DMA capable devices are expected to cancel all outstanding DMA operations
during either 'enter' or 'hold' phases. IOMMUs are expected to reset during
the 'exit' phase and this sequencing makes sure no outstanding DMA request
will fault.
Handling reset in a resettable object
-------------------------------------