[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] amd iommu: Do not adjust paging mode for dom0 devices
On Sunday 06 February 2011 17:58:18 Keir Fraser wrote: > On 01/02/2011 17:34, "Wei Wang2" <wei.wang2@xxxxxxx> wrote: > > Keir > > Here is another small patch to fix consistency issue of paging mode when > > return passthru devices back to dom0. In this case, paging mode should > > not be adjusted, since dom0->max_pages = ~0U. > > The call to get_paging_mode() in amd_iommu_domain_init() looks sensible > enough. Why is a call needed in reassign_device() at all? Checking for dom0 > in reassign_device just looks like a fragile hack. > > -- Keir Keir, amd_iommu_domain_init() is called very early, where get_paging_mode() cannot use domU->max_pages to setup proper io page level for domU. Instead, paging mode of domU has to be initialized as 4 for safety. That is why I want to adjust hd->paging_mode in reassign_device() using domU->max_pages. Since most domU use 2-3 level page tables, always using 4 level might be a waste. But I had a wrong assumption of dom0->max_pages, and consequently when return passthru device back to dom0, following lines in c/s 22825 + if ( target->max_pages > 0 ) + t->paging_mode = get_paging_mode(target->max_pages); will change hd->paging_mode of dom0 from 3 (in most case) to 4 (using get_paging_mode(dom0->max_pages)). Thanks, -Wei _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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