On 14/02/18 18:46, Jacob Pan wrote: > On Mon, 12 Feb 2018 18:33:23 +0000 > Jean-Philippe Brucker <[email protected]> wrote: [...] >> + if (!evt->pasid_valid) >> + return ret; > I guess for not we don't handle PRQ without PASID, right?
No. I'm not sure how to implement it, though there have been some requests (see discussion on 1/37) >> + /* >> + * Special case: PASID Stop Marker (LRW = 0b100) doesn't >> expect a >> + * response. A Stop Marker may be generated when disabling a >> PASID >> + * (issuing a PASID stop request) in some PCI devices. >> + * >> + * When the mm_exit() callback returns from the device >> driver, no page >> + * request is generated for this PASID anymore and >> outstanding ones have >> + * been pushed to the IOMMU (as per PCIe 4.0r1.0 - 6.20.1 >> and 10.4.1.2 - >> + * Managing PASID TLP Prefix Usage). Some PCI devices will >> wait for all >> + * outstanding page requests to come back with a response >> before >> + * completing the PASID stop request. Others do not wait for >> page >> + * responses, and instead issue this Stop Marker that tells >> us when the >> + * PASID can be reallocated. >> + * >> + * We ignore the Stop Marker because: >> + * a. Page requests, which are posted requests, have been >> flushed to the >> + * IOMMU when mm_exit() returns, >> + * b. We flush all fault queues after mm_exit() returns and >> before >> + * freeing the PASID. >> + * >> + * So even though the Stop Marker might be issued by the >> device *after* >> + * the stop request completes, outstanding faults will have >> been dealt >> + * with by the time we free the PASID. >> + */ >> + if (evt->last_req && >> + !(evt->prot & (IOMMU_FAULT_READ | IOMMU_FAULT_WRITE))) >> + return IOMMU_PAGE_RESP_HANDLED; >> + > If we don't expect a page response, shouldn't it be filtered by the > IOMMU vendor driver in the first place? i.e. in the vendor IOMMU driver > PRQ handler, it will sanitize the request anyway, for anything that > does not need response, it will not call iommu_report_device_fault(). Right, we're not doing anything with the stop marker anyway. This encoding is also specific to PCI PRI, and maybe in future architectures, LRW = 0b100 will mean something else and will require a response. So filtering it in the IOMMU driver makes more sense. Thanks, Jean _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
