From patchwork Fri Jan 22 10:13:57 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yanan Wang X-Patchwork-Id: 12038871 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7DA49C4332E for ; Fri, 22 Jan 2021 10:35:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 43F6123A03 for ; Fri, 22 Jan 2021 10:35:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727432AbhAVK0L (ORCPT ); Fri, 22 Jan 2021 05:26:11 -0500 Received: from szxga04-in.huawei.com ([45.249.212.190]:11128 "EHLO szxga04-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727776AbhAVKOw (ORCPT ); Fri, 22 Jan 2021 05:14:52 -0500 Received: from DGGEMS403-HUB.china.huawei.com (unknown [172.30.72.58]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4DMZp50VG5z15x19; Fri, 22 Jan 2021 18:13:01 +0800 (CST) Received: from DESKTOP-TMVL5KK.china.huawei.com (10.174.187.128) by DGGEMS403-HUB.china.huawei.com (10.3.19.203) with Microsoft SMTP Server id 14.3.498.0; Fri, 22 Jan 2021 18:14:03 +0800 From: Yanan Wang To: Marc Zyngier , Will Deacon , "Catalin Marinas" , , , , CC: James Morse , Julien Thierry , Suzuki K Poulose , Gavin Shan , Quentin Perret , , , , Yanan Wang Subject: [RFC PATCH v4 1/2] KVM: arm64: Adjust partial code of hyp stage-1 map and guest stage-2 map Date: Fri, 22 Jan 2021 18:13:57 +0800 Message-ID: <20210122101358.379956-2-wangyanan55@huawei.com> X-Mailer: git-send-email 2.8.4.windows.1 In-Reply-To: <20210122101358.379956-1-wangyanan55@huawei.com> References: <20210122101358.379956-1-wangyanan55@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.174.187.128] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Procedures of hyp stage-1 map and guest stage-2 map are quite different, but they are tied closely by function kvm_set_valid_leaf_pte(). So adjust the relative code for ease of code maintenance in the future. Signed-off-by: Yanan Wang --- arch/arm64/kvm/hyp/pgtable.c | 54 ++++++++++++++++++------------------ 1 file changed, 27 insertions(+), 27 deletions(-) diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c index bdf8e55ed308..2878aaf53b3c 100644 --- a/arch/arm64/kvm/hyp/pgtable.c +++ b/arch/arm64/kvm/hyp/pgtable.c @@ -170,10 +170,9 @@ static void kvm_set_table_pte(kvm_pte_t *ptep, kvm_pte_t *childp) smp_store_release(ptep, pte); } -static bool kvm_set_valid_leaf_pte(kvm_pte_t *ptep, u64 pa, kvm_pte_t attr, - u32 level) +static kvm_pte_t kvm_init_valid_leaf_pte(u64 pa, kvm_pte_t attr, u32 level) { - kvm_pte_t old = *ptep, pte = kvm_phys_to_pte(pa); + kvm_pte_t pte = kvm_phys_to_pte(pa); u64 type = (level == KVM_PGTABLE_MAX_LEVELS - 1) ? KVM_PTE_TYPE_PAGE : KVM_PTE_TYPE_BLOCK; @@ -181,12 +180,7 @@ static bool kvm_set_valid_leaf_pte(kvm_pte_t *ptep, u64 pa, kvm_pte_t attr, pte |= FIELD_PREP(KVM_PTE_TYPE, type); pte |= KVM_PTE_VALID; - /* Tolerate KVM recreating the exact same mapping. */ - if (kvm_pte_valid(old)) - return old == pte; - - smp_store_release(ptep, pte); - return true; + return pte; } static int kvm_pgtable_visitor_cb(struct kvm_pgtable_walk_data *data, u64 addr, @@ -341,12 +335,17 @@ static int hyp_map_set_prot_attr(enum kvm_pgtable_prot prot, static bool hyp_map_walker_try_leaf(u64 addr, u64 end, u32 level, kvm_pte_t *ptep, struct hyp_map_data *data) { + kvm_pte_t new, old = *ptep; u64 granule = kvm_granule_size(level), phys = data->phys; if (!kvm_block_mapping_supported(addr, end, phys, level)) return false; - WARN_ON(!kvm_set_valid_leaf_pte(ptep, phys, data->attr, level)); + /* Tolerate KVM recreating the exact same mapping */ + new = kvm_init_valid_leaf_pte(phys, data->attr, level); + if (old != new && !WARN_ON(kvm_pte_valid(old))) + smp_store_release(ptep, new); + data->phys += granule; return true; } @@ -465,27 +464,29 @@ static bool stage2_map_walker_try_leaf(u64 addr, u64 end, u32 level, kvm_pte_t *ptep, struct stage2_map_data *data) { + kvm_pte_t new, old = *ptep; u64 granule = kvm_granule_size(level), phys = data->phys; if (!kvm_block_mapping_supported(addr, end, phys, level)) return false; - /* - * If the PTE was already valid, drop the refcount on the table - * early, as it will be bumped-up again in stage2_map_walk_leaf(). - * This ensures that the refcount stays constant across a valid to - * valid PTE update. - */ - if (kvm_pte_valid(*ptep)) - put_page(virt_to_page(ptep)); + new = kvm_init_valid_leaf_pte(phys, data->attr, level); + if (kvm_pte_valid(old)) { + /* Tolerate KVM recreating the exact same mapping */ + if (old == new) + goto out; - if (kvm_set_valid_leaf_pte(ptep, phys, data->attr, level)) - goto out; + /* + * There's an existing different valid leaf entry, so perform + * break-before-make. + */ + kvm_set_invalid_pte(ptep); + kvm_call_hyp(__kvm_tlb_flush_vmid_ipa, data->mmu, addr, level); + put_page(virt_to_page(ptep)); + } - /* There's an existing valid leaf entry, so perform break-before-make */ - kvm_set_invalid_pte(ptep); - kvm_call_hyp(__kvm_tlb_flush_vmid_ipa, data->mmu, addr, level); - kvm_set_valid_leaf_pte(ptep, phys, data->attr, level); + smp_store_release(ptep, new); + get_page(virt_to_page(ptep)); out: data->phys += granule; return true; @@ -527,7 +528,7 @@ static int stage2_map_walk_leaf(u64 addr, u64 end, u32 level, kvm_pte_t *ptep, } if (stage2_map_walker_try_leaf(addr, end, level, ptep, data)) - goto out_get_page; + return 0; if (WARN_ON(level == KVM_PGTABLE_MAX_LEVELS - 1)) return -EINVAL; @@ -551,9 +552,8 @@ static int stage2_map_walk_leaf(u64 addr, u64 end, u32 level, kvm_pte_t *ptep, } kvm_set_table_pte(ptep, childp); - -out_get_page: get_page(page); + return 0; } From patchwork Fri Jan 22 10:13:58 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yanan Wang X-Patchwork-Id: 12038869 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 37DCFC43381 for ; Fri, 22 Jan 2021 10:35:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DE84F239D4 for ; Fri, 22 Jan 2021 10:35:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727481AbhAVK03 (ORCPT ); Fri, 22 Jan 2021 05:26:29 -0500 Received: from szxga06-in.huawei.com ([45.249.212.32]:11430 "EHLO szxga06-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727805AbhAVKO5 (ORCPT ); Fri, 22 Jan 2021 05:14:57 -0500 Received: from DGGEMS403-HUB.china.huawei.com (unknown [172.30.72.58]) by szxga06-in.huawei.com (SkyGuard) with ESMTP id 4DMZpR36vYzj8SW; Fri, 22 Jan 2021 18:13:19 +0800 (CST) Received: from DESKTOP-TMVL5KK.china.huawei.com (10.174.187.128) by DGGEMS403-HUB.china.huawei.com (10.3.19.203) with Microsoft SMTP Server id 14.3.498.0; Fri, 22 Jan 2021 18:14:04 +0800 From: Yanan Wang To: Marc Zyngier , Will Deacon , "Catalin Marinas" , , , , CC: James Morse , Julien Thierry , Suzuki K Poulose , Gavin Shan , Quentin Perret , , , , Yanan Wang Subject: [RFC PATCH v4 2/2] KVM: arm64: Filter out the case of only changing permissions from stage-2 map path Date: Fri, 22 Jan 2021 18:13:58 +0800 Message-ID: <20210122101358.379956-3-wangyanan55@huawei.com> X-Mailer: git-send-email 2.8.4.windows.1 In-Reply-To: <20210122101358.379956-1-wangyanan55@huawei.com> References: <20210122101358.379956-1-wangyanan55@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.174.187.128] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org (1) During running time of a a VM with numbers of vCPUs, if some vCPUs access the same GPA almost at the same time and the stage-2 mapping of the GPA has not been built yet, as a result they will all cause translation faults. The first vCPU builds the mapping, and the followed ones end up updating the valid leaf PTE. Note that these vCPUs might want different access permissions (RO, RW, RX, RWX, etc.). (2) It's inevitable that we sometimes will update an existing valid leaf PTE in the map path, and we all perform break-before-make in this case. Then more unnecessary translation faults could be caused if the *break stage* of BBM is just catched by other vCPUs. With (1) and (2), something unsatisfactory could happen: vCPU A causes a translation fault and builds the mapping with RW permissions, vCPU B then update the valid leaf PTE with break-before-make and permissions are updated back to RO. Besides, *break stage* of BBM may trigger more translation faults. Finally, some useless small loops could occur. We can make some optimization to solve above problems: When we need to update a valid leaf PTE in the translation fault handler, let's filter out the case where this update only change access permissions that don't require break-before-make. If there have already been the permissions we want, don't bother to update. If still more permissions need to be added, then update the PTE directly without break-before-make. Signed-off-by: Yanan Wang --- arch/arm64/include/asm/kvm_pgtable.h | 4 ++ arch/arm64/kvm/hyp/pgtable.c | 62 +++++++++++++++++++++------- 2 files changed, 50 insertions(+), 16 deletions(-) diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h index 52ab38db04c7..2bd4e772ca57 100644 --- a/arch/arm64/include/asm/kvm_pgtable.h +++ b/arch/arm64/include/asm/kvm_pgtable.h @@ -157,6 +157,10 @@ void kvm_pgtable_stage2_destroy(struct kvm_pgtable *pgt); * If device attributes are not explicitly requested in @prot, then the * mapping will be normal, cacheable. * + * When there is an existing valid leaf PTE to be updated in this function, + * perform break-before-make only if the parameters to be changed for this + * update require it, otherwise the PTE can be updated directly. + * * Note that this function will both coalesce existing table entries and split * existing block mappings, relying on page-faults to fault back areas outside * of the new mapping lazily. diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c index 2878aaf53b3c..aac1915f9770 100644 --- a/arch/arm64/kvm/hyp/pgtable.c +++ b/arch/arm64/kvm/hyp/pgtable.c @@ -45,6 +45,10 @@ #define KVM_PTE_LEAF_ATTR_HI_S2_XN BIT(54) +#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_XN) + struct kvm_pgtable_walk_data { struct kvm_pgtable *pgt; struct kvm_pgtable_walker *walker; @@ -460,34 +464,60 @@ static int stage2_map_set_prot_attr(enum kvm_pgtable_prot prot, return 0; } +static void stage2_map_update_valid_leaf_pte(u64 addr, u32 level, + kvm_pte_t *ptep, kvm_pte_t new, + struct stage2_map_data *data) +{ + kvm_pte_t old = *ptep; + + /* + * It's inevitable that we sometimes end up updating an existing valid + * leaf PTE on the map path for kinds of reasons, for instance, multiple + * vcpus accessing the same GPA page all cause translation faults on the + * same time. So perform break-before-make here only if the parameters + * to be changed for this update require it, otherwise the PTE can be + * updated directly. + */ + if ((old ^ new) & (~KVM_PTE_LEAF_ATTR_S2_PERMS)) { + kvm_set_invalid_pte(ptep); + kvm_call_hyp(__kvm_tlb_flush_vmid_ipa, data->mmu, addr, level); + smp_store_release(ptep, new); + return; + } + + old ^= KVM_PTE_LEAF_ATTR_HI_S2_XN; + new ^= KVM_PTE_LEAF_ATTR_HI_S2_XN; + new |= old; + + /* + * Update the valid leaf PTE directly without break-before-make if more + * permissions need to be added, and skip the update if there have been + * already the permissions that we want. + */ + if (new != old) { + WRITE_ONCE(*ptep, new ^ KVM_PTE_LEAF_ATTR_HI_S2_XN); + kvm_call_hyp(__kvm_tlb_flush_vmid_ipa, data->mmu, addr, level); + } +} + static bool stage2_map_walker_try_leaf(u64 addr, u64 end, u32 level, kvm_pte_t *ptep, struct stage2_map_data *data) { - kvm_pte_t new, old = *ptep; + kvm_pte_t new; u64 granule = kvm_granule_size(level), phys = data->phys; if (!kvm_block_mapping_supported(addr, end, phys, level)) return false; new = kvm_init_valid_leaf_pte(phys, data->attr, level); - if (kvm_pte_valid(old)) { - /* Tolerate KVM recreating the exact same mapping */ - if (old == new) - goto out; - - /* - * There's an existing different valid leaf entry, so perform - * break-before-make. - */ - kvm_set_invalid_pte(ptep); - kvm_call_hyp(__kvm_tlb_flush_vmid_ipa, data->mmu, addr, level); - put_page(virt_to_page(ptep)); + if (kvm_pte_valid(*ptep)) { + stage2_map_update_valid_leaf_pte(addr, level, ptep, new, data); + } else { + smp_store_release(ptep, new); + get_page(virt_to_page(ptep)); } - smp_store_release(ptep, new); - get_page(virt_to_page(ptep)); -out: data->phys += granule; return true; }