54 lines
2.0 KiB
Diff
54 lines
2.0 KiB
Diff
From 389c3c6b4215c9be3fd784c73af0e9795e796380 Mon Sep 17 00:00:00 2001
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From: Eric Auger <eric.auger@redhat.com>
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Date: Tue, 18 Feb 2025 19:25:35 +0100
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Subject: [PATCH 5/9] docs/devel/reset: Document reset expectations for DMA and
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IOMMU
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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RH-Author: Eric Auger <eric.auger@redhat.com>
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RH-MergeRequest: 341: Fix vIOMMU reset order
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RH-Jira: RHEL-7188
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RH-Acked-by: Peter Xu <peterx@redhat.com>
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RH-Acked-by: Donald Dutile <None>
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RH-Acked-by: Cédric Le Goater <clg@redhat.com>
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RH-Commit: [5/5] be8b9d9e34a2b301430dfa229c6785ab17d3fb16 (eauger1/centos-qemu-kvm)
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To avoid any translation faults, the IOMMUs are expected to be
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reset after the devices they protect. Document that we expect
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DMA requests to be stopped during the 'enter' or 'hold' phase
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while IOMMUs should be reset during the 'exit' phase.
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Signed-off-by: Eric Auger <eric.auger@redhat.com>
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Reviewed-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
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Message-Id: <20250218182737.76722-6-eric.auger@redhat.com>
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Reviewed-by: Peter Xu <peterx@redhat.com>
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Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
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Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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(cherry picked from commit dd6d545e8f2d9a0e8a8c287ec16469f03ef5c198)
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Signed-off-by: Eric Auger <eric.auger@redhat.com>
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---
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docs/devel/reset.rst | 5 +++++
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1 file changed, 5 insertions(+)
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diff --git a/docs/devel/reset.rst b/docs/devel/reset.rst
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index 9746a4e8a0..24ab630465 100644
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--- a/docs/devel/reset.rst
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+++ b/docs/devel/reset.rst
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@@ -123,6 +123,11 @@ The *exit* phase is executed only when the last reset operation ends. Therefore
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the object does not need to care how many of reset controllers it has and how
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many of them have started a reset.
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+DMA capable devices are expected to cancel all outstanding DMA operations
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+during either 'enter' or 'hold' phases. IOMMUs are expected to reset during
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+the 'exit' phase and this sequencing makes sure no outstanding DMA request
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+will fault.
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+
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Handling reset in a resettable object
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-------------------------------------
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--
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2.48.1
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