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 X-Spam-Level: X-Spam-Status: No, score=-17.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 4E8A2C43460 for ; Wed, 21 Apr 2021 05:53:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2CE696142C for ; Wed, 21 Apr 2021 05:53:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235359AbhDUFxc (ORCPT ); Wed, 21 Apr 2021 01:53:32 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:60706 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235353AbhDUFx3 (ORCPT ); Wed, 21 Apr 2021 01:53:29 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1618984375; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=vqV3nZmtiS3HiblM9X32LHWFH0pNEm2EPbe6NxcNwks=; b=BDB5dfpLJOCoiB/tCoDV3QctjgWB4FJM3K8E89T6yzUenBF0qRyT+5LmXQrCCNroJ0xGpj xhAFmGt4rkndIfnW+wH2R1e1jT3fpetyimq076xNvsBv2tU5iWRly+CyJsY+ejQWE/fGFw aC5LItUzPkXRJJ5WRtgT+npIB9zdiu0= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-512-AufqBBdtMVaojJyOUvcMWw-1; Wed, 21 Apr 2021 01:52:53 -0400 X-MC-Unique: AufqBBdtMVaojJyOUvcMWw-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 05E118030A0; Wed, 21 Apr 2021 05:52:52 +0000 (UTC) Received: from [10.64.54.47] (vpn2-54-47.bne.redhat.com [10.64.54.47]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 39B086064B; Wed, 21 Apr 2021 05:52:48 +0000 (UTC) Reply-To: Gavin Shan Subject: Re: [PATCH v4 2/2] kvm/arm64: Try stage2 block mapping for host device MMIO To: Keqian Zhu , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, Marc Zyngier Cc: wanghaibin.wang@huawei.com References: <20210415140328.24200-1-zhukeqian1@huawei.com> <20210415140328.24200-3-zhukeqian1@huawei.com> From: Gavin Shan Message-ID: <960e097d-818b-00bc-b2ee-0da17857f862@redhat.com> Date: Wed, 21 Apr 2021 17:52:58 +1000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.0 MIME-Version: 1.0 In-Reply-To: <20210415140328.24200-3-zhukeqian1@huawei.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Hi Keqian, On 4/16/21 12:03 AM, Keqian Zhu wrote: > The MMIO region of a device maybe huge (GB level), try to use > block mapping in stage2 to speedup both map and unmap. > > Compared to normal memory mapping, we should consider two more > points when try block mapping for MMIO region: > > 1. For normal memory mapping, the PA(host physical address) and > HVA have same alignment within PUD_SIZE or PMD_SIZE when we use > the HVA to request hugepage, so we don't need to consider PA > alignment when verifing block mapping. But for device memory > mapping, the PA and HVA may have different alignment. > > 2. For normal memory mapping, we are sure hugepage size properly > fit into vma, so we don't check whether the mapping size exceeds > the boundary of vma. But for device memory mapping, we should pay > attention to this. > > This adds get_vma_page_shift() to get page shift for both normal > memory and device MMIO region, and check these two points when > selecting block mapping size for MMIO region. > > Signed-off-by: Keqian Zhu > --- > arch/arm64/kvm/mmu.c | 61 ++++++++++++++++++++++++++++++++++++-------- > 1 file changed, 51 insertions(+), 10 deletions(-) > > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c > index c59af5ca01b0..5a1cc7751e6d 100644 > --- a/arch/arm64/kvm/mmu.c > +++ b/arch/arm64/kvm/mmu.c > @@ -738,6 +738,35 @@ transparent_hugepage_adjust(struct kvm_memory_slot *memslot, > return PAGE_SIZE; > } > > +static int get_vma_page_shift(struct vm_area_struct *vma, unsigned long hva) > +{ > + unsigned long pa; > + > + if (is_vm_hugetlb_page(vma) && !(vma->vm_flags & VM_PFNMAP)) > + return huge_page_shift(hstate_vma(vma)); > + > + if (!(vma->vm_flags & VM_PFNMAP)) > + return PAGE_SHIFT; > + > + VM_BUG_ON(is_vm_hugetlb_page(vma)); > + I don't understand how VM_PFNMAP is set for hugetlbfs related vma. I think they are exclusive, meaning the flag is never set for hugetlbfs vma. If it's true, VM_PFNMAP needn't be checked on hugetlbfs vma and the VM_BUG_ON() becomes unnecessary. > + pa = (vma->vm_pgoff << PAGE_SHIFT) + (hva - vma->vm_start); > + > +#ifndef __PAGETABLE_PMD_FOLDED > + if ((hva & (PUD_SIZE - 1)) == (pa & (PUD_SIZE - 1)) && > + ALIGN_DOWN(hva, PUD_SIZE) >= vma->vm_start && > + ALIGN(hva, PUD_SIZE) <= vma->vm_end) > + return PUD_SHIFT; > +#endif > + > + if ((hva & (PMD_SIZE - 1)) == (pa & (PMD_SIZE - 1)) && > + ALIGN_DOWN(hva, PMD_SIZE) >= vma->vm_start && > + ALIGN(hva, PMD_SIZE) <= vma->vm_end) > + return PMD_SHIFT; > + > + return PAGE_SHIFT; > +} > + There is "switch(...)" fallback mechanism in user_mem_abort(). PUD_SIZE/PMD_SIZE can be downgraded accordingly if the addresses fails in the alignment check by fault_supports_stage2_huge_mapping(). I think it would make user_mem_abort() simplified if the logic can be moved to get_vma_page_shift(). Another question if we need the check from fault_supports_stage2_huge_mapping() if VM_PFNMAP area is going to be covered by block mapping. If so, the "switch(...)" fallback mechanism needs to be part of get_vma_page_shift(). > static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > struct kvm_memory_slot *memslot, unsigned long hva, > unsigned long fault_status) > @@ -769,7 +798,10 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > return -EFAULT; > } > > - /* Let's check if we will get back a huge page backed by hugetlbfs */ > + /* > + * Let's check if we will get back a huge page backed by hugetlbfs, or > + * get block mapping for device MMIO region. > + */ > mmap_read_lock(current->mm); > vma = find_vma_intersection(current->mm, hva, hva + 1); > if (unlikely(!vma)) { > @@ -778,15 +810,15 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > return -EFAULT; > } > > - if (is_vm_hugetlb_page(vma)) > - vma_shift = huge_page_shift(hstate_vma(vma)); > - else > - vma_shift = PAGE_SHIFT; > - > - if (logging_active || > - (vma->vm_flags & VM_PFNMAP)) { > + /* > + * logging_active is guaranteed to never be true for VM_PFNMAP > + * memslots. > + */ > + if (logging_active) { > force_pte = true; > vma_shift = PAGE_SHIFT; > + } else { > + vma_shift = get_vma_page_shift(vma, hva); > } > > switch (vma_shift) { > @@ -854,8 +886,17 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > return -EFAULT; > > if (kvm_is_device_pfn(pfn)) { > + /* > + * If the page was identified as device early by looking at > + * the VMA flags, vma_pagesize is already representing the > + * largest quantity we can map. If instead it was mapped > + * via gfn_to_pfn_prot(), vma_pagesize is set to PAGE_SIZE > + * and must not be upgraded. > + * > + * In both cases, we don't let transparent_hugepage_adjust() > + * change things at the last minute. > + */ > device = true; > - force_pte = true; > } else if (logging_active && !write_fault) { > /* > * Only actually map the page as writable if this was a write > @@ -876,7 +917,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > * If we are not forced to use page mapping, check if we are > * backed by a THP and thus use block mapping if possible. > */ > - if (vma_pagesize == PAGE_SIZE && !force_pte) > + if (vma_pagesize == PAGE_SIZE && !(force_pte || device)) > vma_pagesize = transparent_hugepage_adjust(memslot, hva, > &pfn, &fault_ipa); > if (writable) > Thanks, Gavin