Messages in this thread | | | From | Greentime Hu <> | Date | Tue, 15 Sep 2020 11:58:13 +0800 | Subject | Re: [PATCH] riscv: Add sfence.vma after page table changed |
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Palmer Dabbelt <palmer@dabbelt.com> 於 2020年8月5日 週三 上午10:03寫道: > > On Mon, 03 Aug 2020 20:29:32 PDT (-0700), anup@brainfault.org wrote: > > On Tue, Aug 4, 2020 at 8:32 AM Greentime Hu <greentime.hu@sifive.com> wrote: > >> > >> This patch addes local_flush_tlb_page(addr) to use sfence.vma after the > > > > s/addes/adds > > > >> page table changed. That address will be used immediately in > >> memset(nextp, 0, PAGE_SIZE) to cause this issue so we should add the > >> sfence.vma before we use it. > > > > Alternate version of this commit description can be: > > > > Invalidate local TLB after both set_pet() and clear_pte() because the > > address can be used immediately after page table change. > > > >> Fixes: f2c17aabc917 ("RISC-V: Implement compile-time fixed mappings") > >> > >> Reported-by: Syven Wang <syven.wang@sifive.com> > >> Signed-off-by: Syven Wang <syven.wang@sifive.com> > >> Signed-off-by: Greentime Hu <greentime.hu@sifive.com> > >> --- > >> arch/riscv/mm/init.c | 7 +++---- > >> 1 file changed, 3 insertions(+), 4 deletions(-) > >> > >> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c > >> index f4adb3684f3d..29b0f7108054 100644 > >> --- a/arch/riscv/mm/init.c > >> +++ b/arch/riscv/mm/init.c > >> @@ -202,12 +202,11 @@ void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot) > >> > >> ptep = &fixmap_pte[pte_index(addr)]; > >> > >> - if (pgprot_val(prot)) { > >> + if (pgprot_val(prot)) > >> set_pte(ptep, pfn_pte(phys >> PAGE_SHIFT, prot)); > >> - } else { > >> + else > >> pte_clear(&init_mm, addr, ptep); > >> - local_flush_tlb_page(addr); > >> - } > >> + local_flush_tlb_page(addr); > >> } > > arm64 appears to be upgrading all set_pte()s on valid kernel mappings to > include the fence. It looks like the message from 7f0b1bf04511 ("arm64: Fix > barriers used for page table modifications") is out of date, as I can't find > create_mapping() any more. If that was some generic kernel thing then we > should probably upgrade ours as well, but if it was arch/arm64/ code then this > approach seems fine as __set_fixmap() isn't on the hot path -- I guess this is > fine either way, but there may be other issues that the arm64 approach fixes. > > Do you guys happen to remember what was going on here?
Hi Palmer,
Some architectures add cache writeback in set_pte(), just like nds32, csky.
https://github.com/torvalds/linux/blob/master/arch/nds32/include/asm/pgtable.h#L213 https://github.com/torvalds/linux/blob/master/arch/csky/include/asm/pgtable.h#L104
Would you like to pick this patch or should I send another patch to implement it in set_pte()?
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