On Thu, 2014-11-06 at 09:16 -0700, Alex Williamson wrote: > On Thu, 2014-11-06 at 13:54 +0100, Joerg Roedel wrote: > > Hi Alex, > > > > On Tue, Nov 04, 2014 at 09:12:17AM -0700, Alex Williamson wrote: > > > I haven't tested it, but I'm concerned whether this has introduced a > > > domain leak. If we think about the case of unbinding a device from a > > > host driver and attaching it to a domain through the IOMMU API, I think > > > we used to count on this path to call domain_exit(), which made the > > > domain_context_mapped() in intel_iommu_attach_device() "unlikely". With > > > this change, isn't the test in intel_iommu_attach_device() now neither > > > likely nor unlikely and we're only removing the dev_info from the domain > > > and not destroying the domain itself? Thanks, > > > > As I see it, there is no leak. The DMA-API domains are kept in the > > device_domain_list and re-used when the device driver re-attaches. But > > your are right that the unlikely in intel_iommu_attach_device() isn't > > true anymore. We could probably remove it. > > But the domains are unlinked from device_domain_list using > unlink_domain_info() which is called from both domain_remove_dev_info() > and domain_remove_one_dev_info() which are both part of that more > likely, unlikely branch in intel_iommu_attach_device(). So it seems > like any time we switch a device from the DMA-API to the IOMMU-API, we > lose the reference to the domain. Is that incorrect? I'll try to test.
Trying the simple approach, a printk in each of alloc_domain() and free_domain_mem(), this is what I see when I start and stop a VM with an assigned device: alloc_domain(): ffff8801e22ac000 free_domain_mem(ffff8801e22ac000) alloc_domain(): ffff8801e3425c80 The IOMMU API domain is alloc'd and free'd, then a new DMA-API domain is alloc'd. There are no frees of the DMA-API domain. Thanks, Alex -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
