On Thu, Nov 03 2022, Peter Collingbourne <pcc@xxxxxxxxxx> wrote: > From: Catalin Marinas <catalin.marinas@xxxxxxx> > > Initialising the tags and setting PG_mte_tagged flag for a page can race > between multiple set_pte_at() on shared pages or setting the stage 2 pte > via user_mem_abort(). Introduce a new PG_mte_lock flag as PG_arch_3 and > set it before attempting page initialisation. Given that PG_mte_tagged > is never cleared for a page, consider setting this flag to mean page > unlocked and wait on this bit with acquire semantics if the page is > locked: > > - try_page_mte_tagging() - lock the page for tagging, return true if it > can be tagged, false if already tagged. No acquire semantics if it > returns true (PG_mte_tagged not set) as there is no serialisation with > a previous set_page_mte_tagged(). > > - set_page_mte_tagged() - set PG_mte_tagged with release semantics. > > The two-bit locking is based on Peter Collingbourne's idea. > > Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx> > Signed-off-by: Peter Collingbourne <pcc@xxxxxxxxxx> > Reviewed-by: Steven Price <steven.price@xxxxxxx> > Cc: Will Deacon <will@xxxxxxxxxx> > Cc: Marc Zyngier <maz@xxxxxxxxxx> > Cc: Peter Collingbourne <pcc@xxxxxxxxxx> > --- > arch/arm64/include/asm/mte.h | 35 +++++++++++++++++++++++++++++++- > arch/arm64/include/asm/pgtable.h | 4 ++-- > arch/arm64/kernel/cpufeature.c | 2 +- > arch/arm64/kernel/mte.c | 12 +++-------- > arch/arm64/kvm/guest.c | 16 +++++++++------ > arch/arm64/kvm/mmu.c | 2 +- > arch/arm64/mm/copypage.c | 2 ++ > arch/arm64/mm/fault.c | 2 ++ > arch/arm64/mm/mteswap.c | 14 +++++-------- > 9 files changed, 60 insertions(+), 29 deletions(-) Reviewed-by: Cornelia Huck <cohuck@xxxxxxxxxx>
