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Subject: [OASIS Issue Tracker] Commented: (VIRTIO-35) race condition with multi-dword config accesses
[ http://tools.oasis-open.org/issues/browse/VIRTIO-35?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=35492#action_35492 ] Rusty Russell commented on VIRTIO-35: ------------------------------------- https://lists.oasis-open.org/archives/virtio/201310/msg00034.html > race condition with multi-dword config accesses > ----------------------------------------------- > > Key: VIRTIO-35 > URL: http://tools.oasis-open.org/issues/browse/VIRTIO-35 > Project: OASIS Virtual I/O Device (VIRTIO) TC > Issue Type: Bug > Reporter: Michael Tsirkin > > on many architectures, accesses larger than 32 bit can not be atomic. > Thus access to a device config field of >4 bytes is inherently racy > in case field can change. > For example, virtio-blk has > u64 capacity; > The following race can trigger: > driver reads low 32 bit > both low and high 32 bit change > driver reads high 32 bit > as a result, capacity observed is composed of > old low bits and new high bits which does not > make sense. > For legacy devices, spec allowed byte by byte access, > making the race even more common. -- This message is automatically generated by JIRA. - If you think it was sent incorrectly contact one of the administrators: http://tools.oasis-open.org/issues/secure/Administrators.jspa - For more information on JIRA, see: http://www.atlassian.com/software/jira
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