b4 wasn't happy with my copy/paste of the CC list from Fuad's series [1]. CC'ing them here. [1]: https://lore.kernel.org/all/20240222161047.402609-1-tabba@xxxxxxxxxx/ On Tue, Jun 18, 2024 at 05:05:06PM -0700, Elliot Berman wrote: > In arm64 pKVM and QuIC's Gunyah protected VM model, we want to support > grabbing shmem user pages instead of using KVM's guestmemfd. These > hypervisors provide a different isolation model than the CoCo > implementations from x86. KVM's guest_memfd is focused on providing > memory that is more isolated than AVF requires. Some specific examples > include ability to pre-load data onto guest-private pages, dynamically > sharing/isolating guest pages without copy, and (future) migrating > guest-private pages. In sum of those differences after a discussion in > [1] and at PUCK, we want to try to stick with existing shmem and extend > GUP to support the isolation needs for arm64 pKVM and Gunyah. To that > end, we introduce the concept of "exclusive GUP pinning", which enforces > that only one pin of any kind is allowed when using the FOLL_EXCLUSIVE > flag is set. This behavior doesn't affect FOLL_GET or any other folio > refcount operations that don't go through the FOLL_PIN path. > > [1]: https://lore.kernel.org/all/20240319143119.GA2736@willie-the-truck/ > > Tree with patches at: > https://git.codelinaro.org/clo/linux-kernel/gunyah-linux/-/tree/sent/exclusive-gup-v1 > > > Signed-off-by: Elliot Berman <quic_eberman@xxxxxxxxxxx> > --- > Elliot Berman (2): > mm/gup-test: Verify exclusive pinned > mm/gup_test: Verify GUP grabs same pages twice > > Fuad Tabba (3): > mm/gup: Move GUP_PIN_COUNTING_BIAS to page_ref.h > mm/gup: Add an option for obtaining an exclusive pin > mm/gup: Add support for re-pinning a normal pinned page as exclusive > > include/linux/mm.h | 57 ++++---- > include/linux/mm_types.h | 2 + > include/linux/page_ref.h | 74 ++++++++++ > mm/Kconfig | 5 + > mm/gup.c | 265 ++++++++++++++++++++++++++++++---- > mm/gup_test.c | 108 ++++++++++++++ > mm/gup_test.h | 1 + > tools/testing/selftests/mm/gup_test.c | 5 +- > 8 files changed, 457 insertions(+), 60 deletions(-) > --- > base-commit: 6ba59ff4227927d3a8530fc2973b80e94b54d58f > change-id: 20240509-exclusive-gup-66259138bbff > > Best regards, > -- > Elliot Berman <quic_eberman@xxxxxxxxxxx> >
