| Message ID | 20220110223201.31024-4-alex.sierra@amd.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Add MEMORY_DEVICE_COHERENT for coherent device memory mapping | expand |
On 1/10/22 22:31, Alex Sierra wrote: > Avoid long term pinning for Coherent device type pages. This could > interfere with their own device memory manager. For now, we are just > returning error for PIN_LONGTERM Coherent device type pages. Eventually, > these type of pages will get migrated to system memory, once the device > migration pages support is added. > > Signed-off-by: Alex Sierra <alex.sierra@amd.com> > --- > mm/gup.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/mm/gup.c b/mm/gup.c > index 886d6148d3d0..9c8a075d862d 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -1720,6 +1720,12 @@ static long check_and_migrate_movable_pages(unsigned long nr_pages, > * If we get a movable page, since we are going to be pinning > * these entries, try to move them out if possible. > */ > + if (is_device_page(head)) { > + WARN_ON_ONCE(is_device_private_page(head)); > + ret = -EFAULT; > + goto unpin_pages; > + } > + Wouldn't be more efficient for you failing earlier instead of after all the pages are pinned? Filesystem DAX suffers from a somewhat similar issue[0] -- albeit it's more related to blocking FOLL_LONGTERM in gup-fast while gup-slow can still do it. Coherent devmap appears to want to block it in all gup. On another thread Jason was suggesting about having different pgmap::flags to capture these special cases[1] instead of selecting what different pgmap types can do in various different places. [0] https://lore.kernel.org/linux-mm/6a18179e-65f7-367d-89a9-d5162f10fef0@oracle.com/ [1] https://lore.kernel.org/linux-mm/20211019160136.GH3686969@ziepe.ca/
On Thursday, 20 January 2022 11:36:21 PM AEDT Joao Martins wrote: > On 1/10/22 22:31, Alex Sierra wrote: > > Avoid long term pinning for Coherent device type pages. This could > > interfere with their own device memory manager. For now, we are just > > returning error for PIN_LONGTERM Coherent device type pages. Eventually, > > these type of pages will get migrated to system memory, once the device > > migration pages support is added. > > > > Signed-off-by: Alex Sierra <alex.sierra@amd.com> > > --- > > mm/gup.c | 7 +++++++ > > 1 file changed, 7 insertions(+) > > > > diff --git a/mm/gup.c b/mm/gup.c > > index 886d6148d3d0..9c8a075d862d 100644 > > --- a/mm/gup.c > > +++ b/mm/gup.c > > @@ -1720,6 +1720,12 @@ static long check_and_migrate_movable_pages(unsigned long nr_pages, > > * If we get a movable page, since we are going to be pinning > > * these entries, try to move them out if possible. > > */ > > + if (is_device_page(head)) { > > + WARN_ON_ONCE(is_device_private_page(head)); > > + ret = -EFAULT; > > + goto unpin_pages; > > + } > > + > > Wouldn't be more efficient for you failing earlier instead of after all the pages are pinned? Rather than failing I think the plan is to migrate the device coherent pages like we do for ZONE_MOVABLE, so leaving this here is a good place holder until that is done. Currently we are missing some functionality required to do that but I am hoping to post a series fixing that soon. > Filesystem DAX suffers from a somewhat similar issue[0] -- albeit it's more related to > blocking FOLL_LONGTERM in gup-fast while gup-slow can still do it. Coherent devmap appears > to want to block it in all gup. > > On another thread Jason was suggesting about having different pgmap::flags to capture > these special cases[1] instead of selecting what different pgmap types can do in various > different places. > > [0] https://lore.kernel.org/linux-mm/6a18179e-65f7-367d-89a9-d5162f10fef0@oracle.com/ > [1] https://lore.kernel.org/linux-mm/20211019160136.GH3686969@ziepe.ca/ >
diff --git a/mm/gup.c b/mm/gup.c index 886d6148d3d0..9c8a075d862d 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1720,6 +1720,12 @@ static long check_and_migrate_movable_pages(unsigned long nr_pages, * If we get a movable page, since we are going to be pinning * these entries, try to move them out if possible. */ + if (is_device_page(head)) { + WARN_ON_ONCE(is_device_private_page(head)); + ret = -EFAULT; + goto unpin_pages; + } + if (!is_pinnable_page(head)) { if (PageHuge(head)) { if (!isolate_huge_page(head, &movable_page_list)) @@ -1750,6 +1756,7 @@ static long check_and_migrate_movable_pages(unsigned long nr_pages, if (list_empty(&movable_page_list) && !isolation_error_count) return nr_pages; +unpin_pages: if (gup_flags & FOLL_PIN) { unpin_user_pages(pages, nr_pages); } else {
Avoid long term pinning for Coherent device type pages. This could interfere with their own device memory manager. For now, we are just returning error for PIN_LONGTERM Coherent device type pages. Eventually, these type of pages will get migrated to system memory, once the device migration pages support is added. Signed-off-by: Alex Sierra <alex.sierra@amd.com> --- mm/gup.c | 7 +++++++ 1 file changed, 7 insertions(+)