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=-12.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 32FE2C43381 for ; Tue, 5 Mar 2019 11:13:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0A81A2082C for ; Tue, 5 Mar 2019 11:13:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727648AbfCELNb (ORCPT ); Tue, 5 Mar 2019 06:13:31 -0500 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:46622 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726951AbfCELNb (ORCPT ); Tue, 5 Mar 2019 06:13:31 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id B29931596; Tue, 5 Mar 2019 03:13:30 -0800 (PST) Received: from [10.1.196.93] (en101.cambridge.arm.com [10.1.196.93]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E4F143F71D; Tue, 5 Mar 2019 03:13:28 -0800 (PST) Subject: Re: [RFC PATCH] KVM: arm64: Force a PTE mapping when logging is enabled To: yuzenghui@huawei.com, marc.zyngier@arm.com, zenghuiyu96@gmail.com Cc: christoffer.dall@arm.com, punit.agrawal@arm.com, julien.thierry@arm.com, linux-kernel@vger.kernel.org, james.morse@arm.com, wanghaibin.wang@huawei.com, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org References: <1551497728-12576-1-git-send-email-yuzenghui@huawei.com> <20190304171320.GA3984@en101> <32f302eb-ef89-7de4-36b4-3c3df907c732@arm.com> <865b8b0b-e42e-fe03-e3b4-ae2cc5b1b424@huawei.com> From: Suzuki K Poulose Message-ID: Date: Tue, 5 Mar 2019 11:13:27 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: <865b8b0b-e42e-fe03-e3b4-ae2cc5b1b424@huawei.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Zenghui, On 05/03/2019 11:09, Zenghui Yu wrote: > Hi Marc, Suzuki, > > On 2019/3/5 1:34, Marc Zyngier wrote: >> Hi Zenghui, Suzuki, >> >> On 04/03/2019 17:13, Suzuki K Poulose wrote: >>> Hi Zenghui, >>> >>> On Sun, Mar 03, 2019 at 11:14:38PM +0800, Zenghui Yu wrote: >>>> I think there're still some problems in this patch... Details below. >>>> >>>> On Sat, Mar 2, 2019 at 11:39 AM Zenghui Yu wrote: >>>>> >>>>> The idea behind this is: we don't want to keep tracking of huge pages when >>>>> logging_active is true, which will result in performance degradation. We >>>>> still need to set vma_pagesize to PAGE_SIZE, so that we can make use of it >>>>> to force a PTE mapping. >>> >>> Yes, you're right. We are indeed ignoring the force_pte flag. >>> >>>>> >>>>> Cc: Suzuki K Poulose >>>>> Cc: Punit Agrawal >>>>> Signed-off-by: Zenghui Yu >>>>> >>>>> --- >>>>> Atfer looking into https://patchwork.codeaurora.org/patch/647985/ , the >>>>> "vma_pagesize = PAGE_SIZE" logic was not intended to be deleted. As far >>>>> as I can tell, we used to have "hugetlb" to force the PTE mapping, but >>>>> we have "vma_pagesize" currently instead. We should set it properly for >>>>> performance reasons (e.g, in VM migration). Did I miss something important? >>>>> >>>>> --- >>>>> virt/kvm/arm/mmu.c | 7 +++++++ >>>>> 1 file changed, 7 insertions(+) >>>>> >>>>> diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c >>>>> index 30251e2..7d41b16 100644 >>>>> --- a/virt/kvm/arm/mmu.c >>>>> +++ b/virt/kvm/arm/mmu.c >>>>> @@ -1705,6 +1705,13 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, >>>>> (vma_pagesize == PUD_SIZE && kvm_stage2_has_pmd(kvm))) && >>>>> !force_pte) { >>>>> gfn = (fault_ipa & huge_page_mask(hstate_vma(vma))) >> PAGE_SHIFT; >>>>> + } else { >>>>> + /* >>>>> + * Fallback to PTE if it's not one of the stage2 >>>>> + * supported hugepage sizes or the corresponding level >>>>> + * doesn't exist, or logging is enabled. >>>> >>>> First, Instead of "logging is enabled", it should be "force_pte is true", >>>> since "force_pte" will be true when: >>>> >>>> 1) fault_supports_stage2_pmd_mappings() return false; or >>>> 2) "logging is enabled" (e.g, in VM migration). >>>> >>>> Second, fallback some unsupported hugepage sizes (e.g, 64K hugepage with >>>> 4K pages) to PTE is somewhat strange. And it will then _unexpectedly_ >>>> reach transparent_hugepage_adjust(), though no real adjustment will happen >>>> since commit fd2ef358282c ("KVM: arm/arm64: Ensure only THP is candidate >>>> for adjustment"). Keeping "vma_pagesize" there as it is will be better, >>>> right? >>>> >>>> So I'd just simplify the logic like: >>> >>> We could fix this right in the beginning. See patch below: >>> >>>> >>>> } else if (force_pte) { >>>> vma_pagesize = PAGE_SIZE; >>>> } >>>> >>>> >>>> Will send a V2 later and waiting for your comments :) >>> >>> >>> diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c >>> index 30251e2..529331e 100644 >>> --- a/virt/kvm/arm/mmu.c >>> +++ b/virt/kvm/arm/mmu.c >>> @@ -1693,7 +1693,9 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, >>> return -EFAULT; >>> } >>> >>> - vma_pagesize = vma_kernel_pagesize(vma); >>> + /* If we are forced to map at page granularity, force the pagesize here */ >>> + vma_pagesize = force_pte ? PAGE_SIZE : vma_kernel_pagesize(vma); >>> + >>> /* >>> * The stage2 has a minimum of 2 level table (For arm64 see >>> * kvm_arm_setup_stage2()). Hence, we are guaranteed that we can >>> @@ -1701,11 +1703,10 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, >>> * As for PUD huge maps, we must make sure that we have at least >>> * 3 levels, i.e, PMD is not folded. >>> */ >>> - if ((vma_pagesize == PMD_SIZE || >>> - (vma_pagesize == PUD_SIZE && kvm_stage2_has_pmd(kvm))) && >>> - !force_pte) { >>> + if (vma_pagesize == PMD_SIZE || >>> + (vma_pagesize == PUD_SIZE && kvm_stage2_has_pmd(kvm))) >>> gfn = (fault_ipa & huge_page_mask(hstate_vma(vma))) >> PAGE_SHIFT; >>> - } >>> + >>> up_read(¤t->mm->mmap_sem); >>> >>> /* We need minimum second+third level pages */ > > A nicer implementation and easier to understand, thanks! > >> That's pretty interesting, because this is almost what we already have >> in the NV code: >> >> https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/tree/virt/kvm/arm/mmu.c?h=kvm-arm64/nv-wip-v5.0-rc7#n1752 >> >> (note that force_pte is gone in that branch). > > haha :-) sorry about that. I haven't looked into the NV code yet, so ... > > But I'm still wondering: should we fix this wrong mapping size problem > before NV is introduced? Since this problem has not much to do with NV, > and 5.0 has already been released with this problem (and 5.1 will > without fix ...). Yes, we must fix it. I will soon send out a patch copying on it. Its just that I find some more issues around forcing the PTE mappings with PUD huge pages. I will send something out soon. Cheers Suzuki 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=-12.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_PASS 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 923C2C43381 for ; Tue, 5 Mar 2019 11:13:46 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 5294F20848 for ; Tue, 5 Mar 2019 11:13:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="W8XEt9Ys" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5294F20848 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender:Content-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=89lka+Ghmp44Rh9Q4mkZQ4VyqTyqiWU2b0hnqVMNbAE=; b=W8XEt9YsbsAj139FBv/Lb09A0 6YRq4yWXNRIE+friGx1o8Ia/O3GWMnMXlNrrftmM5k9Xzfn7chLc147UNZesscFZYDo2CP5S8ToLS ZvSG+mNHnH6lVLaIeTUvbki5mgKp02+44OW9OBTFwFeX9HcNgSpb4bGwiJhLOO/hT/edhEcXAyU+B CiBpmolhCbO+DuKcZAmtiAqSG3J/nn6En5M/KO/c+nZQUgyNPUMpBf0IXZR8TjSaFSPRn4Df9iScZ hwDz3kjLwFajpKTFhXdDyaJIwEJTqQ9wailQazWnQaNZPQre5nGyEAT5eHMAg7ZuiTEcP1y3MhjRU cQ7KJHoBQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1h180z-0002Sl-2U; Tue, 05 Mar 2019 11:13:41 +0000 Received: from foss.arm.com ([217.140.101.70]) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1h180o-0002Ii-VO for linux-arm-kernel@lists.infradead.org; Tue, 05 Mar 2019 11:13:32 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id B29931596; Tue, 5 Mar 2019 03:13:30 -0800 (PST) Received: from [10.1.196.93] (en101.cambridge.arm.com [10.1.196.93]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E4F143F71D; Tue, 5 Mar 2019 03:13:28 -0800 (PST) Subject: Re: [RFC PATCH] KVM: arm64: Force a PTE mapping when logging is enabled To: yuzenghui@huawei.com, marc.zyngier@arm.com, zenghuiyu96@gmail.com References: <1551497728-12576-1-git-send-email-yuzenghui@huawei.com> <20190304171320.GA3984@en101> <32f302eb-ef89-7de4-36b4-3c3df907c732@arm.com> <865b8b0b-e42e-fe03-e3b4-ae2cc5b1b424@huawei.com> From: Suzuki K Poulose Message-ID: Date: Tue, 5 Mar 2019 11:13:27 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: <865b8b0b-e42e-fe03-e3b4-ae2cc5b1b424@huawei.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190305_031331_017151_906CC6E7 X-CRM114-Status: GOOD ( 21.83 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: julien.thierry@arm.com, punit.agrawal@arm.com, linux-kernel@vger.kernel.org, christoffer.dall@arm.com, james.morse@arm.com, wanghaibin.wang@huawei.com, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Zenghui, On 05/03/2019 11:09, Zenghui Yu wrote: > Hi Marc, Suzuki, > > On 2019/3/5 1:34, Marc Zyngier wrote: >> Hi Zenghui, Suzuki, >> >> On 04/03/2019 17:13, Suzuki K Poulose wrote: >>> Hi Zenghui, >>> >>> On Sun, Mar 03, 2019 at 11:14:38PM +0800, Zenghui Yu wrote: >>>> I think there're still some problems in this patch... Details below. >>>> >>>> On Sat, Mar 2, 2019 at 11:39 AM Zenghui Yu wrote: >>>>> >>>>> The idea behind this is: we don't want to keep tracking of huge pages when >>>>> logging_active is true, which will result in performance degradation. We >>>>> still need to set vma_pagesize to PAGE_SIZE, so that we can make use of it >>>>> to force a PTE mapping. >>> >>> Yes, you're right. We are indeed ignoring the force_pte flag. >>> >>>>> >>>>> Cc: Suzuki K Poulose >>>>> Cc: Punit Agrawal >>>>> Signed-off-by: Zenghui Yu >>>>> >>>>> --- >>>>> Atfer looking into https://patchwork.codeaurora.org/patch/647985/ , the >>>>> "vma_pagesize = PAGE_SIZE" logic was not intended to be deleted. As far >>>>> as I can tell, we used to have "hugetlb" to force the PTE mapping, but >>>>> we have "vma_pagesize" currently instead. We should set it properly for >>>>> performance reasons (e.g, in VM migration). Did I miss something important? >>>>> >>>>> --- >>>>> virt/kvm/arm/mmu.c | 7 +++++++ >>>>> 1 file changed, 7 insertions(+) >>>>> >>>>> diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c >>>>> index 30251e2..7d41b16 100644 >>>>> --- a/virt/kvm/arm/mmu.c >>>>> +++ b/virt/kvm/arm/mmu.c >>>>> @@ -1705,6 +1705,13 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, >>>>> (vma_pagesize == PUD_SIZE && kvm_stage2_has_pmd(kvm))) && >>>>> !force_pte) { >>>>> gfn = (fault_ipa & huge_page_mask(hstate_vma(vma))) >> PAGE_SHIFT; >>>>> + } else { >>>>> + /* >>>>> + * Fallback to PTE if it's not one of the stage2 >>>>> + * supported hugepage sizes or the corresponding level >>>>> + * doesn't exist, or logging is enabled. >>>> >>>> First, Instead of "logging is enabled", it should be "force_pte is true", >>>> since "force_pte" will be true when: >>>> >>>> 1) fault_supports_stage2_pmd_mappings() return false; or >>>> 2) "logging is enabled" (e.g, in VM migration). >>>> >>>> Second, fallback some unsupported hugepage sizes (e.g, 64K hugepage with >>>> 4K pages) to PTE is somewhat strange. And it will then _unexpectedly_ >>>> reach transparent_hugepage_adjust(), though no real adjustment will happen >>>> since commit fd2ef358282c ("KVM: arm/arm64: Ensure only THP is candidate >>>> for adjustment"). Keeping "vma_pagesize" there as it is will be better, >>>> right? >>>> >>>> So I'd just simplify the logic like: >>> >>> We could fix this right in the beginning. See patch below: >>> >>>> >>>> } else if (force_pte) { >>>> vma_pagesize = PAGE_SIZE; >>>> } >>>> >>>> >>>> Will send a V2 later and waiting for your comments :) >>> >>> >>> diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c >>> index 30251e2..529331e 100644 >>> --- a/virt/kvm/arm/mmu.c >>> +++ b/virt/kvm/arm/mmu.c >>> @@ -1693,7 +1693,9 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, >>> return -EFAULT; >>> } >>> >>> - vma_pagesize = vma_kernel_pagesize(vma); >>> + /* If we are forced to map at page granularity, force the pagesize here */ >>> + vma_pagesize = force_pte ? PAGE_SIZE : vma_kernel_pagesize(vma); >>> + >>> /* >>> * The stage2 has a minimum of 2 level table (For arm64 see >>> * kvm_arm_setup_stage2()). Hence, we are guaranteed that we can >>> @@ -1701,11 +1703,10 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, >>> * As for PUD huge maps, we must make sure that we have at least >>> * 3 levels, i.e, PMD is not folded. >>> */ >>> - if ((vma_pagesize == PMD_SIZE || >>> - (vma_pagesize == PUD_SIZE && kvm_stage2_has_pmd(kvm))) && >>> - !force_pte) { >>> + if (vma_pagesize == PMD_SIZE || >>> + (vma_pagesize == PUD_SIZE && kvm_stage2_has_pmd(kvm))) >>> gfn = (fault_ipa & huge_page_mask(hstate_vma(vma))) >> PAGE_SHIFT; >>> - } >>> + >>> up_read(¤t->mm->mmap_sem); >>> >>> /* We need minimum second+third level pages */ > > A nicer implementation and easier to understand, thanks! > >> That's pretty interesting, because this is almost what we already have >> in the NV code: >> >> https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/tree/virt/kvm/arm/mmu.c?h=kvm-arm64/nv-wip-v5.0-rc7#n1752 >> >> (note that force_pte is gone in that branch). > > haha :-) sorry about that. I haven't looked into the NV code yet, so ... > > But I'm still wondering: should we fix this wrong mapping size problem > before NV is introduced? Since this problem has not much to do with NV, > and 5.0 has already been released with this problem (and 5.1 will > without fix ...). Yes, we must fix it. I will soon send out a patch copying on it. Its just that I find some more issues around forcing the PTE mappings with PUD huge pages. I will send something out soon. Cheers Suzuki _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel