El 15/08/15 a les 17.30, Jason Harmening ha escrit: > On 08/15/15 08:05, Roger Pau Monné wrote: >> El 14/08/15 a les 22.08, Jason A. Harmening ha escrit: >>> Author: jah >>> Date: Fri Aug 14 20:08:16 2015 >>> New Revision: 286787 >>> URL: https://svnweb.freebsd.org/changeset/base/286787 >>> >>> Log: >>> Use pmap_quick_enter_page() to handle bouncing of unmapped buffers in the >>> x86 busdma_bounce implementation. Also treat user buffers as unmapped. >>> This allows two things: >>> 1. Sync'ing bounced maps in non-sleepable contexts. The physcopy* calls >>> previously used could sleep on sf_buf operations in some cases. >>> 2. Sync'ing user buffers outside the context of the owning process >> >> AFAICT this will break the Xen port. physcopy* uses uiomove_fromphys >> that on the amd64 port is able to deal with pages outside of the DMAP. >> OTOH pmap_quick_enter_page is not able to deal with pages outside of the >> DMAP, and will simply panic. >> >> Roger. >> > > Is it actually possible for those non-dom0 pages to be used for I/O that > passes through busdma?
Yes, Qemu uses them as buffers to read/write syscalls. > If it is, then it would be easy to make > pmap_quick_enter_page() handle them by adding a pcpu pageframe similar > to what we do for i386. pmap_map_io_transient contains some of this logic, but it uses vmem_alloc (with M_WAITOK) instead of a pcpu pageframe, which defeats part of the purpose of this change and cannot be used as-is. Roger. _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
