This series adds fast gup support to riscv. The First patch fixes a bug in __p*d_free_tlb(). Per the riscv privileged spec, if non-leaf PTEs I.E pmd, pud or p4d is modified, a sfence.vma is a must. The 2nd patch is a preparation patch. The last two patches do the real work: In order to implement fast gup we need to ensure that the page table walker is protected from page table pages being freed from under it. riscv situation is more complicated than other architectures: some riscv platforms may use IPI to perform TLB shootdown, for example, those platforms which support AIA, usually the riscv_ipi_for_rfence is true on these platforms; some riscv platforms may rely on the SBI to perform TLB shootdown, usually the riscv_ipi_for_rfence is false on these platforms. To keep software pagetable walkers safe in this case we switch to RCU based table free (MMU_GATHER_RCU_TABLE_FREE). See the comment below 'ifdef CONFIG_MMU_GATHER_RCU_TABLE_FREE' in include/asm-generic/tlb.h for more details. This patch enables MMU_GATHER_RCU_TABLE_FREE, then use *tlb_remove_page_ptdesc() for those platforms which use IPI to perform TLB shootdown; *tlb_remove_ptdesc() for those platforms which use SBI to perform TLB shootdown; Both case mean that disabling interrupts will block the free and protect the fast gup page walker. So after the 3rd patch, everything is well prepared, let's select HAVE_FAST_GUP if MMU. Jisheng Zhang (4): riscv: tlb: fix __p*d_free_tlb() riscv: tlb: convert __p*d_free_tlb() to inline functions riscv: enable MMU_GATHER_RCU_TABLE_FREE for SMP && MMU riscv: enable HAVE_FAST_GUP if MMU arch/riscv/Kconfig | 2 ++ arch/riscv/include/asm/pgalloc.h | 53 +++++++++++++++++++++++++++----- arch/riscv/include/asm/pgtable.h | 6 ++++ arch/riscv/include/asm/tlb.h | 18 +++++++++++ 4 files changed, 71 insertions(+), 8 deletions(-) -- 2.40.0
