On 6/18/2025 7:35 PM, Anup Patel wrote:
> The gstage_set_pte() and gstage_op_pte() should flush TLB only when
> a leaf PTE changes so that unnecessary TLB flushes can be avoided.
>
> Reviewed-by: Atish Patra <atishp@rivosinc.com>
> Signed-off-by: Anup Patel <apatel@ventanamicro.com>
> ---
> arch/riscv/kvm/mmu.c | 14 +++++++++-----
> 1 file changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/arch/riscv/kvm/mmu.c b/arch/riscv/kvm/mmu.c
> index 1087ea74567b..29f1bd853a66 100644
> --- a/arch/riscv/kvm/mmu.c
> +++ b/arch/riscv/kvm/mmu.c
> @@ -167,9 +167,11 @@ static int gstage_set_pte(struct kvm *kvm, u32 level,
> ptep = &next_ptep[gstage_pte_index(addr, current_level)];
> }
>
> - set_pte(ptep, *new_pte);
> - if (gstage_pte_leaf(ptep))
> - gstage_remote_tlb_flush(kvm, current_level, addr);
> + if (pte_val(*ptep) != pte_val(*new_pte)) {
> + set_pte(ptep, *new_pte);
> + if (gstage_pte_leaf(ptep))
> + gstage_remote_tlb_flush(kvm, current_level, addr);
> + }
>
> return 0;
> }
> @@ -229,7 +231,7 @@ static void gstage_op_pte(struct kvm *kvm, gpa_t addr,
> pte_t *ptep, u32 ptep_level, enum gstage_op op)
> {
> int i, ret;
> - pte_t *next_ptep;
> + pte_t old_pte, *next_ptep;
> u32 next_ptep_level;
> unsigned long next_page_size, page_size;
>
> @@ -258,11 +260,13 @@ static void gstage_op_pte(struct kvm *kvm, gpa_t addr,
> if (op == GSTAGE_OP_CLEAR)
> put_page(virt_to_page(next_ptep));
> } else {
> + old_pte = *ptep;
> if (op == GSTAGE_OP_CLEAR)
> set_pte(ptep, __pte(0));
> else if (op == GSTAGE_OP_WP)
> set_pte(ptep, __pte(pte_val(ptep_get(ptep)) & ~_PAGE_WRITE));
> - gstage_remote_tlb_flush(kvm, ptep_level, addr);
> + if (pte_val(*ptep) != pte_val(old_pte))
> + gstage_remote_tlb_flush(kvm, ptep_level, addr);
> }
> }
>
Reviewed-by: Nutty Liu <liujingqi@lanxincomputing.com>
Thanks,
Nutty