Messages in this thread | | | From | Wan ZongShun <> | Date | Mon, 11 Jul 2016 18:05:51 +0800 | Subject | Re: [PATCH] iommu/amd: Fix unity mapping initialization race |
| |
> >> Sorry, why you still say this 'init_device_table_dma' can block DMA? >> I just think this function will enable DMA transfer, since we set >> the V and TV bits, right? or I misunderstand what "block DMA" mean? > > When the V and TV bits are not set, it means that all DMA from that > device-id is forwared untranslated by the IOMMU. But if we set V and TV > it means that there is translation information, and the IOMMU translates > the requests using the rest of the DTE information. As all other bits > are 0, this means that page-table-level is 0 (== no page-table) and that > the global IW and IR bits are 0 too (== no read and write permissions). > So all requests are blocked. >
Clearly.
Thanks.
> > > Joerg > > _______________________________________________ > iommu mailing list > iommu@lists.linux-foundation.org > https://lists.linuxfoundation.org/mailman/listinfo/iommu
-- --- Vincent Wan(Zongshun) www.mcuos.com
| |