On Mon, Jul 28, 2025 at 12:07:59PM -0700, Nicolin Chen wrote: > On Sun, Jul 27, 2025 at 01:25:01PM -0300, Jason Gunthorpe wrote: > > On Tue, Jul 22, 2025 at 02:58:21PM -0700, Nicolin Chen wrote: > > > > /* > > > > * This is called on the dma mapping fast path so avoid locking. This > > > > * is racy, but we have an expectation that the driver will setup its > > > > * DMAs inside probe while still single threaded to avoid racing. > > > > */ > > > > if (dev->iommu && !READ_ONCE(dev->iommu->attach_deferred)) > > > > > > This triggers a build error as attach_deferred is a bit-field. So I > > > am changing it from "u32 attach_deferred:1" to "bool" for this. > > > > Bleck, that seems undesirable. > > But inevitable for READ_ONCE :( I guess drop the READ_ONCE change > > > And, to keep the original logic, I think it should be: > > > if (!dev->iommu || !READ_ONCE(dev->iommu->attach_deferred)) > > > > That doesn't seem right, if there is no iommu by the time a driver is > > probed there never will be an iommu and this device should be running > > in direct mode only. > > Well, the current function does: > if (dev->iommu && dev->iommu->attach_deferred) > return __iommu_attach_device(domain, dev); > return 0; > > So, matching to that logic, it would be: > if (!dev->iommu || !dev->iommu->attach_deferred) > return 0; > return __iommu_attach_device(domain, dev); > then add guard(mutex). Yeah Ok Jason
