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=-15.3 required=3.0 tests=BAYES_00, 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 DC6B0C433ED for ; Wed, 21 Apr 2021 06:37:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8CA4561426 for ; Wed, 21 Apr 2021 06:37:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235973AbhDUGhk (ORCPT ); Wed, 21 Apr 2021 02:37:40 -0400 Received: from szxga05-in.huawei.com ([45.249.212.191]:17020 "EHLO szxga05-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229536AbhDUGhj (ORCPT ); Wed, 21 Apr 2021 02:37:39 -0400 Received: from DGGEMS410-HUB.china.huawei.com (unknown [172.30.72.60]) by szxga05-in.huawei.com (SkyGuard) with ESMTP id 4FQ9kN3TrFzPshQ; Wed, 21 Apr 2021 14:34:04 +0800 (CST) Received: from [10.174.187.224] (10.174.187.224) by DGGEMS410-HUB.china.huawei.com (10.3.19.210) with Microsoft SMTP Server id 14.3.498.0; Wed, 21 Apr 2021 14:36:56 +0800 Subject: Re: [PATCH v4 2/2] kvm/arm64: Try stage2 block mapping for host device MMIO To: Gavin Shan , , , , References: <20210415140328.24200-1-zhukeqian1@huawei.com> <20210415140328.24200-3-zhukeqian1@huawei.com> <960e097d-818b-00bc-b2ee-0da17857f862@redhat.com> CC: Marc Zyngier , From: Keqian Zhu Message-ID: <105a403a-e48b-15bc-44ff-0ff34f7d2194@huawei.com> Date: Wed, 21 Apr 2021 14:36:55 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.7.1 MIME-Version: 1.0 In-Reply-To: <960e097d-818b-00bc-b2ee-0da17857f862@redhat.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.187.224] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 2021/4/21 15:52, Gavin Shan wrote: > 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. Yes, but we're not sure all drivers follow this rule. Add a BUG_ON() is a way to catch issue. > >> + 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(). Yes, Good suggestion. My idea is that we can keep this series simpler and do further optimization in another patch series. Do you mind to send a patch? Thanks, Keqian