[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] | [List Home]
Subject: [OASIS Issue Tracker] (VIRTIO-154) Document VIRTIO_F_IOMMU_PLATFORM reserved feature bit (33)
[ https://issues.oasis-open.org/browse/VIRTIO-154?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ] Michael S. Tsirkin updated VIRTIO-154: -------------------------------------- Proposal: Document VIRTIO_F_IOMMU_PLATFORM that's already in use by Linux guests. See message: Date: Thu, 20 Oct 2016 18:20:01 +0100 From: Will Deacon <will.deacon@arm.com> To: virtio-dev@lists.oasis-open.org Cc: Will Deacon <will.deacon@arm.com>, "Michael S. Tsirkin" <mst@redhat.com>, Stefan Hajnoczi <stefanha@redhat.com> Subject: [PATCH v2] context: Document VIRTIO_F_IOMMU_PLATFORM reserved feature bit (33) Message-Id: <1476984001-431-1-git-send-email-will.deacon@arm.com> https://lists.oasis-open.org/archives/virtio-dev/201610/msg00121.html was: Document VIRTIO_F_IOMMU_PLATFORM that's already in use by Linux guests. http://markmail.org/message/b3px2pk2qyldwkwg > Document VIRTIO_F_IOMMU_PLATFORM reserved feature bit (33) > ---------------------------------------------------------- > > Key: VIRTIO-154 > URL: https://issues.oasis-open.org/browse/VIRTIO-154 > Project: OASIS Virtual I/O Device (VIRTIO) TC > Issue Type: Bug > Affects Versions: virtio 1.0 cs04 > Environment: Reported-by: Will Deacon <will.deacon@arm.com> > Reporter: Michael S. Tsirkin > Assignee: Michael S. Tsirkin > Fix For: virtio 1.1 cs01 > > > On most virtio systems, physical addresses are provided from the driver > to the device and subsequently used to access memory directly. However, > some systems feature an IOMMU that complicates things slightly: > - The IOMMU might require configuration for DMA to work at all. Once > configured, the driver must pass bus addresses to the device, which > are then translated by the IOMMU into physical addresses in memory. > - The IOMMU might be bypassed by virtio DMA. In this case, physical > addresses must still be provided to the device by the driver, even > though an IOMMU appears to be present. > This has been solved by the addition of a new reserved feature bit, > VIRTIO_F_IOMMU_PLATFORM, to describe the two cases above. Legacy systems > will not negotiate the feature, and therefore continue to operate > directly on physical addresses. -- This message was sent by Atlassian JIRA (v6.2.2#6258)
[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] | [List Home]