On Tue, Mar 09, 2021 at 12:40:04PM -0400, Jason Gunthorpe wrote: > On Tue, Mar 09, 2021 at 08:29:51AM -0700, Alex Williamson wrote: > > On Tue, 9 Mar 2021 08:46:09 -0400 > > Jason Gunthorpe <jgg@xxxxxxxxxx> wrote: > > > > > On Tue, Mar 09, 2021 at 03:49:09AM +0000, Zengtao (B) wrote: > > > > Hi guys: > > > > > > > > Thanks for the helpful comments, after rethinking the issue, I have proposed > > > > the following change: > > > > 1. follow_pte instead of follow_pfn. > > > > > > Still no on follow_pfn, you don't need it once you use vmf_insert_pfn > > > > vmf_insert_pfn() only solves the BUG_ON, follow_pte() is being used > > here to determine whether the translation is already present to avoid > > both duplicate work in inserting the translation and allocating a > > duplicate vma tracking structure. > > Oh.. Doing something stateful in fault is not nice at all > > I would rather see __vfio_pci_add_vma() search the vma_list for dups > than call follow_pfn/pte.. It seems to me that searching vma list is still the simplest way to fix the problem for the current code base. I see io_remap_pfn_range() is also used in the new series - maybe that'll need to be moved to where PCI_COMMAND_MEMORY got turned on/off in the new series (I just noticed remap_pfn_range modifies vma flags..), as you suggested in the other email. Thanks, -- Peter Xu
