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Mon, 03 Aug 2026 03:10:52 -0700 (PDT) Date: Mon, 3 Aug 2026 11:08:45 +0100 In-Reply-To: <20260803100904.3563942-1-vdonnefort@google.com> Mime-Version: 1.0 References: <20260803100904.3563942-1-vdonnefort@google.com> X-Mailer: git-send-email 2.55.0.508.g3f0d502094-goog Message-ID: <20260803100904.3563942-2-vdonnefort@google.com> Subject: [PATCH 01/20] KVM: arm64: Prefault host stage-2 entries on block split From: Vincent Donnefort To: maz@kernel.org, oupton@kernel.org, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org Cc: joey.gouly@arm.com, seiden@linux.ibm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, kernel-team@android.com, fuad.tabba@linux.dev, qperret@google.com, keirf@google.com, Vincent Donnefort Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260803_031055_581238_FC1D39BB X-CRM114-Status: GOOD ( 14.66 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Keir Fraser For the host stage-2 that is idmap, we can avoid lazy-mapping on block splitting by propagate existing valid mappings to neighbouring entries of the new table. Co-developed-by: Quentin Perret Signed-off-by: Keir Fraser Signed-off-by: Vincent Donnefort diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c index b74dd5ce1efd..34f78a58cded 100644 --- a/arch/arm64/kvm/hyp/pgtable.c +++ b/arch/arm64/kvm/hyp/pgtable.c @@ -1030,10 +1030,39 @@ static int stage2_map_walk_table_pre(const struct kvm_pgtable_visit_ctx *ctx, return 0; } +static void stage2_map_prefault_idmap(const struct kvm_pgtable_visit_ctx *ctx, kvm_pte_t *ptep) +{ + kvm_pte_t block_pte = ctx->old; + u64 pa; + int i; + + if (!kvm_pte_valid(block_pte)) + return; + + pa = ALIGN_DOWN(ctx->addr, kvm_granule_size(ctx->level)); + for (i = 0; i < PTRS_PER_PTE; ++i, ++ptep, pa += kvm_granule_size(ctx->level + 1)) { + kvm_pte_t pte = kvm_init_valid_leaf_pte(pa, block_pte, ctx->level + 1); + + /* + * Skip ptes in the range being modified by the caller if we're + * installing last level entries. Otherwise, we need to + * temporarily put in a valid mapping to make sure the + * prefaulting logic is triggered on the next + * stage2_map_walk_leaf(). This adds an unnecessary TLBI as + * we'll presumably re-break the freshly installed block, but + * that should happen very infrequently. + */ + if ((ctx->level < (KVM_PGTABLE_LAST_LEVEL - 1)) || + (pa < ctx->addr) || (pa >= ctx->end)) + *ptep = pte; + } +} + static int stage2_map_walk_leaf(const struct kvm_pgtable_visit_ctx *ctx, struct stage2_map_data *data) { struct kvm_pgtable_mm_ops *mm_ops = ctx->mm_ops; + struct kvm_pgtable *pgt = data->mmu->pgt; kvm_pte_t *childp, new; int ret; @@ -1051,6 +1080,9 @@ static int stage2_map_walk_leaf(const struct kvm_pgtable_visit_ctx *ctx, if (!childp) return -ENOMEM; + if (pgt->flags & KVM_PGTABLE_S2_IDMAP) + stage2_map_prefault_idmap(ctx, childp); + if (!stage2_try_break_pte(ctx, data->mmu)) { mm_ops->put_page(childp); return -EAGAIN; -- 2.55.0.508.g3f0d502094-goog