From: Leonardo Bras <leo.bras@arm.com> As a first step of changing the encoding for the Stage2 PTE descriptor, introduce the DBM bit, and adapt every usage of writable to use the DBM bit (51) instead of S2AP[1]/Dirty bit (7). With DBM as the write permission bit and S2AP[1] as the dirty state, the encoding follows the FEAT_S2PIE principle of managing permissions and dirty state independently. For this step, we convert usages of RW(Dirty) -> WD(DBM|Dirty): every writable mapping sets both bits, read-only mappings clear both, and no behaviour changes. Link: https://lore.kernel.org/all/20260901171558.2674031-2-leo.bras@arm.com/ Signed-off-by: Leonardo Bras <leo.bras@arm.com> [zhengtian: keep the nested walker reading writability from S2AP[1] alone, document why, and reword the commit message] Signed-off-by: Tian Zheng <zhengtian10@huawei.com> --- arch/arm64/include/asm/kvm_pgtable.h | 3 +++ arch/arm64/kvm/hyp/pgtable.c | 7 ++++--- arch/arm64/kvm/nested.c | 5 +++++ arch/arm64/kvm/ptdump.c | 4 ++-- 4 files changed, 14 insertions(+), 5 deletions(-) diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h index 41a8687938eb..37baa86d6fd8 100644 --- a/arch/arm64/include/asm/kvm_pgtable.h +++ b/arch/arm64/include/asm/kvm_pgtable.h @@ -93,10 +93,13 @@ typedef u64 kvm_pte_t; #define KVM_PTE_LEAF_ATTR_HI_S2_XN GENMASK(54, 53) +#define KVM_PTE_LEAF_ATTR_HI_S2_DBM BIT(51) + #define KVM_PTE_LEAF_ATTR_HI_S1_GP BIT(50) #define KVM_PTE_LEAF_ATTR_S2_PERMS (KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R | \ KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W | \ + KVM_PTE_LEAF_ATTR_HI_S2_DBM | \ KVM_PTE_LEAF_ATTR_HI_S2_XN) /* pKVM invalid pte encodings */ diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c index b74dd5ce1efd..50f4d3a74f77 100644 --- a/arch/arm64/kvm/hyp/pgtable.c +++ b/arch/arm64/kvm/hyp/pgtable.c @@ -732,7 +732,7 @@ static int stage2_set_prot_attr(struct kvm_pgtable *pgt, enum kvm_pgtable_prot p attr |= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R; if (prot & KVM_PGTABLE_PROT_W) - attr |= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W; + attr |= KVM_PTE_LEAF_ATTR_HI_S2_DBM | KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W; if (!kvm_lpa2_is_enabled()) attr |= FIELD_PREP(KVM_PTE_LEAF_ATTR_LO_S2_SH, sh); @@ -753,7 +753,7 @@ enum kvm_pgtable_prot kvm_pgtable_stage2_pte_prot(kvm_pte_t pte) if (pte & KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R) prot |= KVM_PGTABLE_PROT_R; - if (pte & KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W) + if (pte & KVM_PTE_LEAF_ATTR_HI_S2_DBM) prot |= KVM_PGTABLE_PROT_W; switch (FIELD_GET(KVM_PTE_LEAF_ATTR_HI_S2_XN, pte)) { @@ -1288,6 +1288,7 @@ static int stage2_update_leaf_attrs(struct kvm_pgtable *pgt, u64 addr, int kvm_pgtable_stage2_wrprotect(struct kvm_pgtable *pgt, u64 addr, u64 size) { return stage2_update_leaf_attrs(pgt, addr, size, 0, + KVM_PTE_LEAF_ATTR_HI_S2_DBM | KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W, NULL, NULL, KVM_PGTABLE_WALK_IGNORE_EAGAIN); @@ -1368,7 +1369,7 @@ int kvm_pgtable_stage2_relax_perms(struct kvm_pgtable *pgt, u64 addr, set |= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R; if (prot & KVM_PGTABLE_PROT_W) - set |= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W; + set |= KVM_PTE_LEAF_ATTR_HI_S2_DBM | KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W; if (prot & KVM_PGTABLE_PROT_X) { ret = stage2_set_xn_attr(prot, &xn); diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c index b191365d97cc..4d7f52f4bc09 100644 --- a/arch/arm64/kvm/nested.c +++ b/arch/arm64/kvm/nested.c @@ -388,6 +388,11 @@ static int walk_nested_s2_pgd(struct kvm_vcpu *vcpu, phys_addr_t ipa, (ipa & GENMASK_ULL(addr_bottom - 1, 0)); out->output = paddr; out->block_size = 1UL << ((3 - level) * stride + wi->pgshift); + /* + * L1 descriptors keep the legacy encoding: S2AP[1] is the write + * permission, and DBM is RES0 (the L1-visible HAFDBS is limited + * to AF-only). + */ out->readable = desc & KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R; out->writable = desc & KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W; out->level = level; diff --git a/arch/arm64/kvm/ptdump.c b/arch/arm64/kvm/ptdump.c index 69899797dbad..b0cb8d84a9e9 100644 --- a/arch/arm64/kvm/ptdump.c +++ b/arch/arm64/kvm/ptdump.c @@ -40,8 +40,8 @@ static const struct ptdump_prot_bits stage2_pte_bits[] = { .clear = " ", }, { - .mask = KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W, - .val = KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W, + .mask = KVM_PTE_LEAF_ATTR_HI_S2_DBM, + .val = KVM_PTE_LEAF_ATTR_HI_S2_DBM, .set = "W", .clear = " ", }, -- 2.43.0