From: ShihPo Hung <shihpo.hung@xxxxxxxxxx> commit bf587caae305ae3b4393077fb22c98478ee55755 upstream. Because RISC-V compliant implementations can cache invalid entries in TLB, an SFENCE.VMA is necessary after changes to the page table. This patch adds an SFENCE.vma for the vmalloc_fault path. Signed-off-by: ShihPo Hung <shihpo.hung@xxxxxxxxxx> [paul.walmsley@xxxxxxxxxx: reversed tab->whitespace conversion, wrapped comment lines] Signed-off-by: Paul Walmsley <paul.walmsley@xxxxxxxxxx> Cc: Palmer Dabbelt <palmer@xxxxxxxxxx> Cc: Albert Ou <aou@xxxxxxxxxxxxxxxxx> Cc: Paul Walmsley <paul.walmsley@xxxxxxxxxx> Cc: linux-riscv@xxxxxxxxxxxxxxxxxxx Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/riscv/mm/fault.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) --- a/arch/riscv/mm/fault.c +++ b/arch/riscv/mm/fault.c @@ -29,6 +29,7 @@ #include <asm/pgalloc.h> #include <asm/ptrace.h> +#include <asm/tlbflush.h> /* * This routine handles page faults. It determines the address and the @@ -281,6 +282,18 @@ vmalloc_fault: pte_k = pte_offset_kernel(pmd_k, addr); if (!pte_present(*pte_k)) goto no_context; + + /* + * The kernel assumes that TLBs don't cache invalid + * entries, but in RISC-V, SFENCE.VMA specifies an + * ordering constraint, not a cache flush; it is + * necessary even after writing invalid entries. + * Relying on flush_tlb_fix_spurious_fault would + * suffice, but the extra traps reduce + * performance. So, eagerly SFENCE.VMA. + */ + local_flush_tlb_page(addr); + return; } }
