On Wed, 26 Aug 2009 03:41:20 am Christoph Hellwig wrote: > As various people wanted to know how the various data integrity patches > I've send out recently play together here's a small writeup on what > issues we have in QEMU and how to fix it: Classic mail. Thanks for the massive and coherent clue injection! > Action plan for the guest drivers: > > - virtio-blk needs to advertise ordered queue by default. > This makes cache=writethrough safe on virtio. >From a guest POV, that's "we don't know, let's say we're ordered because that may make us safer". Of course, it may not help: how much does it cost to drain the queue? The bug, IMHO is that we *should* know. And in future I'd like to fix that, either by adding an VIRTIO_BLK_F_ORDERED feature, or a VIRTIO_BLK_F_UNORDERED feature. > Action plan for QEMU: > > - IDE needs to set the write cache enabled bit > - virtio needs to implement a cache flush command and advertise it > (also needs a small change to the host driver) So, virtio-blk needs to be enhanced for this as well. Thanks! Rusty. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
