> -----Original Message----- > From: Roger Pau Monne > Sent: 01 August 2018 17:15 > To: Paul Durrant <paul.durr...@citrix.com> > Cc: xen-devel@lists.xenproject.org; Stefano Stabellini > <sstabell...@kernel.org>; Wei Liu <wei.l...@citrix.com>; George Dunlap > <george.dun...@citrix.com>; Andrew Cooper > <andrew.coop...@citrix.com>; Ian Jackson <ian.jack...@citrix.com>; Tim > (Xen.org) <t...@xen.org>; Julien Grall <julien.gr...@arm.com>; Jan Beulich > <jbeul...@suse.com> > Subject: Re: [Xen-devel] [PATCH v4 01/15] re-work commit 3e06b989 > "IOMMU: make page table population preemptible"... > > On Wed, Aug 01, 2018 at 02:40:14PM +0100, Paul Durrant wrote: > > ...to simplify the implementation and turn need_iommu back into a > boolean. > > > > As noted in [1] the tri-state nature of need_iommu after commit 3e06b989 > is > > confusing, as is the implementation of pre-emption using relmem_list. > > > > This patch instead uses a simple count of pages already populated stored in > > the x86 variant of struct arch_iommu and skips over that number of pages > > if arch_iommu_populate_page_table() is re-invoked after pre-emption. > > Urg, all this is quite ugly. It would be quite better if the need for > an IOMMU was decided before populating the p2m (ie: at domain_create > time by passing an extra XEN_DOMCTL_CDF_iommu or some such), so that > the normal addition of RAM would also populate the IOMMU page tables > if not shared.
Given the problems that Jan has highlighted with using a skip count and essentially being forced to mess with the domain's page list, I think your suggestion is best. Then we can entirely bin arch_iommu_populate_page_table(). That is a bigger piece of work though so in the interest of no blocking the rest of this series I'll drop this patch and replace it with a simpler patch that's just sufficient to make need_iommu boolean again. Paul > > > [1] https://lists.xenproject.org/archives/html/xen-devel/2018- > 07/msg01870.html > > > > Signed-off-by: Paul Durrant <paul.durr...@citrix.com> > > Reviewed-by: Roger Pau Monné <roger....@citrix.com> > > Thanks, Roger. _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
