From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 48DD1519E12 for ; Wed, 30 Sep 2026 17:23:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790789024; cv=none; b=HdC9DSiyFGBwtDKVkkdFzUc5bMMY0h5mEujU6k3QPQ4kJq7ucLkcKZvtQwgjm3oPmQngsF8qI9TaTk65SLLgMmCOPoYPpNig7v00Xz24cimA973h7xOmTKGcEd4yWrlYk/NMVYhlNjlHzvGEKIJN0xTkaAZJK67H5PQrv2f6VyM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790789024; c=relaxed/simple; bh=cu7+TuF4iOJLVQBarMTLvn8c4+pOh0ctODB9kp4SISg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ZqJhSRDTNv+gu2fWnEH7qVHXA+OZoD2PtK41E2gFZV4KGSOXGlG1YBARhYTok87yDN0CuV3hxJ22UUFH7SlU8W/hU7HDDEtFigJjP1IChkm/Fzx3/WHNyvd5WtkPK5vOfTFoSB1hxYEGh86awb0T/fZJkhPN/lNufzGlsXiYJJM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=s3HgTofF; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="s3HgTofF" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 60F9E168F; Wed, 30 Sep 2026 10:23:38 -0700 (PDT) Received: from LeoBrasDK.cambridge.arm.com (LeoBrasDK.cambridge.arm.com [10.2.212.21]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E528E3F86F; Wed, 30 Sep 2026 10:23:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1790789021; bh=cu7+TuF4iOJLVQBarMTLvn8c4+pOh0ctODB9kp4SISg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=s3HgTofFLWe44G+SZwXkIBMpaBtvAcQUNN+46z0tm5v2TBDA6ZrORcZTHv7Z5/8/m 1NAS6MGJmPJXvqtSYS0rQlzb5oR9YCvvJIBJk7Ed+HUplbDOUZB+1Mrrh7CnYCgA/M uISjLg675UJ+EQMeauUmi3wu1Enp2zCRTnD9AHIU= From: Leonardo Bras To: Marc Zyngier , Oliver Upton , Fuad Tabba , Joey Gouly , Steffen Eiden , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , Mark Rutland , Leonardo Bras , Raghavendra Rao Ananta Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org Subject: [PATCH v4 2/3] KVM: arm64: Introduce KVM_PGTABLE_WALK_SKIP_LEVEL* walk flags Date: Wed, 30 Sep 2026 18:22:22 +0100 Message-ID: <20260930172226.2459423-4-leo.bras@arm.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930172226.2459423-2-leo.bras@arm.com> References: <20260930172226.2459423-2-leo.bras@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=5694; i=leo.bras@arm.com; h=from:subject; bh=cu7+TuF4iOJLVQBarMTLvn8c4+pOh0ctODB9kp4SISg=; b=owGbwMvMwCX2pizjszvTwvWMp9WSGLL2uvp++DXla6vdr7DJOp0uCbyzOGQqp32PNy9nuL9wq slyO8U1HaUsDGJcDLJiiiyyj+av4vk+JePIlR8LYOawMoEMYeDiFICJJLQy/BWV2ZMvNWG7/OcZ J3YKrAm423FppmD86pWelU4/Xtun7H/B8D9UjyF+P8/BB1bTrmx/qXIiP37HtCm7TlSVnfvY5mb 7QJUJAA== X-Developer-Key: i=leo.bras@arm.com; a=openpgp; fpr=36E6C95AE0F111CC5B6F4D2E688C33F8A0C5B0C5 Content-Transfer-Encoding: 8bit Add new walking flags KVM_PGTABLE_WALK_SKIP_LEVEL{0-3}. When used, they make the kvm_pgtable_walk() skip the given level, as well as levels higher than that. Being able to skip levels substancially decreases the runtime of a pagetable walk when the callback function does nothing on that level. Signed-off-by: Leonardo Bras --- arch/arm64/include/asm/kvm_pgtable.h | 14 ++++++++++++++ arch/arm64/kvm/hyp/pgtable.c | 16 +++++++++++++--- 2 files changed, 27 insertions(+), 3 deletions(-) diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h index 41a8687938eb..5f37ceef8d63 100644 --- a/arch/arm64/include/asm/kvm_pgtable.h +++ b/arch/arm64/include/asm/kvm_pgtable.h @@ -311,31 +311,45 @@ typedef bool (*kvm_pgtable_force_pte_cb_t)(u64 addr, u64 end, * @KVM_PGTABLE_WALK_SHARED: Indicates the page-tables may be shared * with other software walkers. * @KVM_PGTABLE_WALK_IGNORE_EAGAIN: Don't terminate the walk early if * the walker returns -EAGAIN. * @KVM_PGTABLE_WALK_SKIP_BBM_TLBI: Visit and update table entries * without Break-before-make's * TLB invalidation. * @KVM_PGTABLE_WALK_SKIP_CMO: Visit and update table entries * without Cache maintenance * operations required. + * @KVM_PGTABLE_WALK_SKIP_LEVEL0: Skip visiting level 0+ entries + * @KVM_PGTABLE_WALK_SKIP_LEVEL1: Skip visiting level 1+ entries + * @KVM_PGTABLE_WALK_SKIP_LEVEL2: Skip visiting level 2+ entries + * @KVM_PGTABLE_WALK_SKIP_LEVEL3: Skip visiting level 3 entries */ enum kvm_pgtable_walk_flags { KVM_PGTABLE_WALK_LEAF = BIT(0), KVM_PGTABLE_WALK_TABLE_PRE = BIT(1), KVM_PGTABLE_WALK_TABLE_POST = BIT(2), KVM_PGTABLE_WALK_SHARED = BIT(3), KVM_PGTABLE_WALK_IGNORE_EAGAIN = BIT(4), KVM_PGTABLE_WALK_SKIP_BBM_TLBI = BIT(5), KVM_PGTABLE_WALK_SKIP_CMO = BIT(6), + /* SKIP_LEVEL* flags should not be split nor reordered */ + KVM_PGTABLE_WALK_SKIP_LEVEL0 = BIT(7), + KVM_PGTABLE_WALK_SKIP_LEVEL1 = BIT(8), + KVM_PGTABLE_WALK_SKIP_LEVEL2 = BIT(9), + KVM_PGTABLE_WALK_SKIP_LEVEL3 = BIT(10), }; +#define KVM_PGTABLE_WALK_SKIP_LEVELS (KVM_PGTABLE_WALK_SKIP_LEVEL0 | \ + KVM_PGTABLE_WALK_SKIP_LEVEL1 | \ + KVM_PGTABLE_WALK_SKIP_LEVEL2 | \ + KVM_PGTABLE_WALK_SKIP_LEVEL3 ) + struct kvm_pgtable_visit_ctx { kvm_pte_t *ptep; kvm_pte_t old; void *arg; struct kvm_pgtable_mm_ops *mm_ops; u64 start; u64 addr; u64 end; s8 level; enum kvm_pgtable_walk_flags flags; diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c index 7a51f78b6446..80744478c810 100644 --- a/arch/arm64/kvm/hyp/pgtable.c +++ b/arch/arm64/kvm/hyp/pgtable.c @@ -137,20 +137,27 @@ static bool kvm_pgtable_walk_continue(const struct kvm_pgtable_walker *walker, * Ignore the return code altogether for walkers outside a fault handler * (e.g. write protecting a range of memory) and chug along with the * page table walk. */ if (r == -EAGAIN) return walker->flags & KVM_PGTABLE_WALK_IGNORE_EAGAIN; return !r; } +static bool kvm_pgtable_skip_level(s8 level, enum kvm_pgtable_walk_flags flags) +{ + u32 skip = FIELD_GET(KVM_PGTABLE_WALK_SKIP_LEVELS, flags); + + return unlikely(skip && level >= ffs(skip) - 1); +} + static int __kvm_pgtable_walk(struct kvm_pgtable_walk_data *data, struct kvm_pgtable_mm_ops *mm_ops, kvm_pteref_t pgtable, s8 level); static inline int __kvm_pgtable_visit(struct kvm_pgtable_walk_data *data, struct kvm_pgtable_mm_ops *mm_ops, kvm_pteref_t pteref, s8 level) { enum kvm_pgtable_walk_flags flags = data->walker->flags; kvm_pte_t *ptep = kvm_dereference_pteref(data->walker, pteref); struct kvm_pgtable_visit_ctx ctx = { @@ -185,35 +192,35 @@ static inline int __kvm_pgtable_visit(struct kvm_pgtable_walk_data *data, * into a newly installed or replaced table. */ if (reload) { ctx.old = READ_ONCE(*ptep); table = kvm_pte_table(ctx.old, level); } if (!kvm_pgtable_walk_continue(data->walker, ret)) return ret; - if (!table) { + if (!table || kvm_pgtable_skip_level(level + 1, ctx.flags)) { data->addr = ALIGN_DOWN(data->addr, kvm_granule_size(level)); data->addr += kvm_granule_size(level); goto out; } childp = (kvm_pteref_t)kvm_pte_follow(ctx.old, mm_ops); ret = __kvm_pgtable_walk(data, mm_ops, childp, level + 1); if (!kvm_pgtable_walk_continue(data->walker, ret)) return ret; - if (ctx.flags & KVM_PGTABLE_WALK_TABLE_POST) +out: + if (table && ctx.flags & KVM_PGTABLE_WALK_TABLE_POST) ret = kvm_pgtable_visitor_cb(data, &ctx, KVM_PGTABLE_WALK_TABLE_POST); -out: if (kvm_pgtable_walk_continue(data->walker, ret)) return 0; return ret; } static int __kvm_pgtable_walk(struct kvm_pgtable_walk_data *data, struct kvm_pgtable_mm_ops *mm_ops, kvm_pteref_t pgtable, s8 level) { u32 idx; @@ -242,20 +249,23 @@ static int _kvm_pgtable_walk(struct kvm_pgtable *pgt, struct kvm_pgtable_walk_da u32 idx; int ret = 0; u64 limit = BIT(pgt->ia_bits); if (data->addr > limit || data->end > limit) return -ERANGE; if (!pgt->pgd) return -EINVAL; + if (kvm_pgtable_skip_level(pgt->start_level, data->walker->flags)) + return 0; + for (idx = kvm_pgd_page_idx(pgt, data->addr); data->addr < data->end; ++idx) { kvm_pteref_t pteref = &pgt->pgd[idx * PTRS_PER_PTE]; ret = __kvm_pgtable_walk(data, pgt->mm_ops, pteref, pgt->start_level); if (ret) break; } return ret; } -- 2.55.0