[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Problem with PV disk and iSCSI
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 Gary Grebus schreef: > I've run into a problem on 3.1.2 with an HVM guest using PV disks. In > dom0, the physical disk is accessed using iSCSI. The symptom is that > applications in dom0 which are monitoring the iSCSI network interface > (e.g. tcpdump) die with EFAULT errors. > > When the block I/O completes, it looks like blkback is doing a > GNTTABOP_unmap_grant_ref on a guest page, even though the dom0 kernel > has done get_page() on it and still holds references. > > The page had been passed through iSCSI into the network stack, so it > ends up referenced by one or more skb's. Because there was an AF_PACKET > socket open, a clone of the skb ends up queued for an indeterminate > amount on that socket queue. When the application finally gets around > to reading the data, the page is no longer mapped, and the read fails > trying to copy the data out of the kernel. > > Has anyone else seen anything similar? I mentioned tcpdump, but the > problem also shows up with dhcpcd, which needs to process packets at the > ethernet layer. > > I'm thinking blkback will have to make a dom0 copy of the page before > doing the unmap if there are still extra references? I'm running the same setup. Are you using iSCSI over the same interface as your Xen bridge? Stefan -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.7 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFHrLThYH1+F2Rqwn0RCgwNAJ4my+4sQvRxUzIIYp88GKY04I4j0wCfU0FN 0zHBUpww1N7mSaMV4CLnjEo= =Q+wF -----END PGP SIGNATURE----- _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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