From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id AE60BC05027 for ; Mon, 6 Feb 2023 09:21:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229590AbjBFJVZ (ORCPT ); Mon, 6 Feb 2023 04:21:25 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58230 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230088AbjBFJVS (ORCPT ); Mon, 6 Feb 2023 04:21:18 -0500 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5493D4C2C for ; Mon, 6 Feb 2023 01:21:10 -0800 (PST) Received: from dggpeml500005.china.huawei.com (unknown [172.30.72.56]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4P9LLM228jzJsJ0; Mon, 6 Feb 2023 17:19:23 +0800 (CST) Received: from [10.174.186.51] (10.174.186.51) by dggpeml500005.china.huawei.com (7.185.36.59) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.34; Mon, 6 Feb 2023 17:21:02 +0800 Subject: Re: [PATCH 3/9] KVM: arm64: Add kvm_pgtable_stage2_split() To: Ricardo Koller , , , , , CC: , , , , , , , , , , , , , , Xiexiangyou , References: <20230113035000.480021-1-ricarkol@google.com> <20230113035000.480021-4-ricarkol@google.com> From: Zheng Chuan Message-ID: <59f0d41e-d8ac-dab3-9136-af48efe55578@huawei.com> Date: Mon, 6 Feb 2023 17:20:42 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20230113035000.480021-4-ricarkol@google.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.186.51] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggpeml500005.china.huawei.com (7.185.36.59) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Hi, Ricardo On 2023/1/13 11:49, Ricardo Koller wrote: > Add a new stage2 function, kvm_pgtable_stage2_split(), for splitting a > range of huge pages. This will be used for eager-splitting huge pages > into PAGE_SIZE pages. The goal is to avoid having to split huge pages > on write-protection faults, and instead use this function to do it > ahead of time for large ranges (e.g., all guest memory in 1G chunks at > a time). > > No functional change intended. This new function will be used in a > subsequent commit. > > Signed-off-by: Ricardo Koller > --- > arch/arm64/include/asm/kvm_pgtable.h | 29 ++++++++++++ > arch/arm64/kvm/hyp/pgtable.c | 67 ++++++++++++++++++++++++++++ > 2 files changed, 96 insertions(+) > > diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h > index 8ad78d61af7f..5fbdc1f259fd 100644 > --- a/arch/arm64/include/asm/kvm_pgtable.h > +++ b/arch/arm64/include/asm/kvm_pgtable.h > @@ -644,6 +644,35 @@ bool kvm_pgtable_stage2_is_young(struct kvm_pgtable *pgt, u64 addr); > */ > int kvm_pgtable_stage2_flush(struct kvm_pgtable *pgt, u64 addr, u64 size); > > +/** > + * kvm_pgtable_stage2_split() - Split a range of huge pages into leaf PTEs pointing > + * to PAGE_SIZE guest pages. > + * @pgt: Page-table structure initialised by kvm_pgtable_stage2_init*(). > + * @addr: Intermediate physical address from which to split. > + * @size: Size of the range. > + * @mc: Cache of pre-allocated and zeroed memory from which to allocate > + * page-table pages. > + * > + * @addr and the end (@addr + @size) are effectively aligned down and up to > + * the top level huge-page block size. This is an exampe using 1GB > + * huge-pages and 4KB granules. > + * > + * [---input range---] > + * : : > + * [--1G block pte--][--1G block pte--][--1G block pte--][--1G block pte--] > + * : : > + * [--2MB--][--2MB--][--2MB--][--2MB--] > + * : : > + * [ ][ ][:][ ][ ][ ][ ][ ][:][ ][ ][ ] > + * : : > + * > + * Return: 0 on success, negative error code on failure. Note that > + * kvm_pgtable_stage2_split() is best effort: it tries to break as many > + * blocks in the input range as allowed by the size of the memcache. It > + * will fail it wasn't able to break any block. > + */ > +int kvm_pgtable_stage2_split(struct kvm_pgtable *pgt, u64 addr, u64 size, void *mc); > + > /** > * kvm_pgtable_walk() - Walk a page-table. > * @pgt: Page-table structure initialised by kvm_pgtable_*_init(). > diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c > index 0dee13007776..db9d1a28769b 100644 > --- a/arch/arm64/kvm/hyp/pgtable.c > +++ b/arch/arm64/kvm/hyp/pgtable.c > @@ -1229,6 +1229,73 @@ int kvm_pgtable_stage2_create_removed(struct kvm_pgtable *pgt, > return 0; > } > > +struct stage2_split_data { > + struct kvm_s2_mmu *mmu; > + void *memcache; > +}; > + > +static int stage2_split_walker(const struct kvm_pgtable_visit_ctx *ctx, > + enum kvm_pgtable_walk_flags visit) > +{ > + struct stage2_split_data *data = ctx->arg; > + struct kvm_pgtable_mm_ops *mm_ops = ctx->mm_ops; > + kvm_pte_t pte = ctx->old, new, *childp; > + enum kvm_pgtable_prot prot; > + void *mc = data->memcache; > + u32 level = ctx->level; > + u64 phys; > + int ret; > + > + /* Nothing to split at the last level */ > + if (level == KVM_PGTABLE_MAX_LEVELS - 1) > + return 0; > + > + /* We only split valid block mappings */ > + if (!kvm_pte_valid(pte) || kvm_pte_table(pte, ctx->level)) > + return 0; > + IIUC, It should be !kvm_pte_table(pte, ctx->level)? also, the kvm_pte_table includes the level check and kvm_pte_valid, so, it just be like: - /* Nothing to split at the last level */ - if (level == KVM_PGTABLE_MAX_LEVELS - 1) - return 0; - - /* We only split valid block mappings */ + if (!kvm_pte_table(pte, ctx->level)) + return 0; > + phys = kvm_pte_to_phys(pte); > + prot = kvm_pgtable_stage2_pte_prot(pte); > + > + ret = kvm_pgtable_stage2_create_removed(data->mmu->pgt, &new, phys, > + level, prot, mc); > + if (ret) > + return ret; > + > + if (!stage2_try_break_pte(ctx, data->mmu)) { > + childp = kvm_pte_follow(new, mm_ops); > + kvm_pgtable_stage2_free_removed(mm_ops, childp, level); > + mm_ops->put_page(childp); > + return -EAGAIN; > + } > + > + /* > + * Note, the contents of the page table are guaranteed to be > + * made visible before the new PTE is assigned because > + * stage2_make_pte() writes the PTE using smp_store_release(). > + */ > + stage2_make_pte(ctx, new); > + dsb(ishst); > + return 0; > +} > + > +int kvm_pgtable_stage2_split(struct kvm_pgtable *pgt, > + u64 addr, u64 size, void *mc) > +{ > + struct stage2_split_data split_data = { > + .mmu = pgt->mmu, > + .memcache = mc, > + }; > + > + struct kvm_pgtable_walker walker = { > + .cb = stage2_split_walker, > + .flags = KVM_PGTABLE_WALK_LEAF, > + .arg = &split_data, > + }; > + > + return kvm_pgtable_walk(pgt, addr, size, &walker); > +} > + > int __kvm_pgtable_stage2_init(struct kvm_pgtable *pgt, struct kvm_s2_mmu *mmu, > struct kvm_pgtable_mm_ops *mm_ops, > enum kvm_pgtable_stage2_flags flags, > -- Regards. Chuan