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=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,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 8E566C433E0 for ; Fri, 15 May 2020 15:48:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 69B21207BB for ; Fri, 15 May 2020 15:48:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="MdE8He2L" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726438AbgEOPsb (ORCPT ); Fri, 15 May 2020 11:48:31 -0400 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:59794 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726183AbgEOPsb (ORCPT ); Fri, 15 May 2020 11:48:31 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1589557708; h=from:from: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=jLy3MggFTUYiDsD6jQF0VKdzDmlUnQApL7rI5weuDj0=; b=MdE8He2L6CZmmmxAKFW0oyrdb0gl0319UNfQDQYH7Rh77unhaqMXI2bdVyO9vJzbkAf13R R5XLMzvI9HcfEZPnNJyYmbPR1GonjMrZ5bU0lr05zBbx+rxjA43ulYX0bOIP1dV96BqJmQ oF2stjxfZtJ6I4nSCyPD5K9gmExUwgI= 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-360-C-1v2t1yMOCLnpy6UoyxUg-1; Fri, 15 May 2020 11:48:23 -0400 X-MC-Unique: C-1v2t1yMOCLnpy6UoyxUg-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 2B699107AFCC; Fri, 15 May 2020 15:48:21 +0000 (UTC) Received: from w520.home (ovpn-112-50.phx2.redhat.com [10.3.112.50]) by smtp.corp.redhat.com (Postfix) with ESMTP id 98BF812A4D; Fri, 15 May 2020 15:48:19 +0000 (UTC) Date: Fri, 15 May 2020 09:48:19 -0600 From: Alex Williamson To: Kirti Wankhede Cc: , , , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH Kernel v20 6/8] vfio iommu: Update UNMAP_DMA ioctl to get dirty bitmap before unmap Message-ID: <20200515094819.58ce1756@w520.home> In-Reply-To: <41c5c3aa-6c03-def5-41e4-2803d0aa825c@nvidia.com> References: <1589488667-9683-1-git-send-email-kwankhede@nvidia.com> <1589488667-9683-7-git-send-email-kwankhede@nvidia.com> <20200514212706.036a336a@x1.home> <5256f488-2d11-eb0f-6980-eea23f4d3019@nvidia.com> <20200514234726.03c2e345@x1.home> <268ec129-a1cb-530a-c9b2-7ec53ddf4d17@nvidia.com> <20200515073135.2370a17d@x1.home> <41c5c3aa-6c03-def5-41e4-2803d0aa825c@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Fri, 15 May 2020 21:00:32 +0530 Kirti Wankhede wrote: > On 5/15/2020 7:01 PM, Alex Williamson wrote: > > On Fri, 15 May 2020 12:17:03 +0530 > > Kirti Wankhede wrote: > > > >> On 5/15/2020 11:17 AM, Alex Williamson wrote: > >>> On Fri, 15 May 2020 09:46:43 +0530 > >>> Kirti Wankhede wrote: > >>> > >>>> On 5/15/2020 8:57 AM, Alex Williamson wrote: > >>>>> On Fri, 15 May 2020 02:07:45 +0530 > >>>>> Kirti Wankhede wrote: > >>>>> > >>>>>> DMA mapped pages, including those pinned by mdev vendor drivers, might > >>>>>> get unpinned and unmapped while migration is active and device is still > >>>>>> running. For example, in pre-copy phase while guest driver could access > >>>>>> those pages, host device or vendor driver can dirty these mapped pages. > >>>>>> Such pages should be marked dirty so as to maintain memory consistency > >>>>>> for a user making use of dirty page tracking. > >>>>>> > >>>>>> To get bitmap during unmap, user should allocate memory for bitmap, set > >>>>>> it all zeros, set size of allocated memory, set page size to be > >>>>>> considered for bitmap and set flag VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP. > >>>>>> > >>>>>> Signed-off-by: Kirti Wankhede > >>>>>> Reviewed-by: Neo Jia > >>>>>> --- > >>>>>> drivers/vfio/vfio_iommu_type1.c | 77 ++++++++++++++++++++++++++++++++++------- > >>>>>> include/uapi/linux/vfio.h | 10 ++++++ > >>>>>> 2 files changed, 75 insertions(+), 12 deletions(-) > >>>>>> > >>>>>> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c > >>>>>> index b76d3b14abfd..a1dc57bcece5 100644 > >>>>>> --- a/drivers/vfio/vfio_iommu_type1.c > >>>>>> +++ b/drivers/vfio/vfio_iommu_type1.c > >>>>>> @@ -195,11 +195,15 @@ static void vfio_unlink_dma(struct vfio_iommu *iommu, struct vfio_dma *old) > >>>>>> static int vfio_dma_bitmap_alloc(struct vfio_dma *dma, size_t pgsize) > >>>>>> { > >>>>>> uint64_t npages = dma->size / pgsize; > >>>>>> + size_t bitmap_size; > >>>>>> > >>>>>> if (npages > DIRTY_BITMAP_PAGES_MAX) > >>>>>> return -EINVAL; > >>>>>> > >>>>>> - dma->bitmap = kvzalloc(DIRTY_BITMAP_BYTES(npages), GFP_KERNEL); > >>>>>> + /* Allocate extra 64 bits which are used for bitmap manipulation */ > >>>>>> + bitmap_size = DIRTY_BITMAP_BYTES(npages) + sizeof(u64); > >>>>>> + > >>>>>> + dma->bitmap = kvzalloc(bitmap_size, GFP_KERNEL); > >>>>>> if (!dma->bitmap) > >>>>>> return -ENOMEM; > >>>>>> > >>>>>> @@ -999,23 +1003,25 @@ static int verify_bitmap_size(uint64_t npages, uint64_t bitmap_size) > >>>>>> } > >>>>>> > >>>>>> static int vfio_dma_do_unmap(struct vfio_iommu *iommu, > >>>>>> - struct vfio_iommu_type1_dma_unmap *unmap) > >>>>>> + struct vfio_iommu_type1_dma_unmap *unmap, > >>>>>> + struct vfio_bitmap *bitmap) > >>>>>> { > >>>>>> - uint64_t mask; > >>>>>> struct vfio_dma *dma, *dma_last = NULL; > >>>>>> - size_t unmapped = 0; > >>>>>> + size_t unmapped = 0, pgsize; > >>>>>> int ret = 0, retries = 0; > >>>>>> + unsigned long pgshift; > >>>>>> > >>>>>> mutex_lock(&iommu->lock); > >>>>>> > >>>>>> - mask = ((uint64_t)1 << __ffs(iommu->pgsize_bitmap)) - 1; > >>>>>> + pgshift = __ffs(iommu->pgsize_bitmap); > >>>>>> + pgsize = (size_t)1 << pgshift; > >>>>>> > >>>>>> - if (unmap->iova & mask) { > >>>>>> + if (unmap->iova & (pgsize - 1)) { > >>>>>> ret = -EINVAL; > >>>>>> goto unlock; > >>>>>> } > >>>>>> > >>>>>> - if (!unmap->size || unmap->size & mask) { > >>>>>> + if (!unmap->size || unmap->size & (pgsize - 1)) { > >>>>>> ret = -EINVAL; > >>>>>> goto unlock; > >>>>>> } > >>>>>> @@ -1026,9 +1032,15 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu, > >>>>>> goto unlock; > >>>>>> } > >>>>>> > >>>>>> - WARN_ON(mask & PAGE_MASK); > >>>>>> -again: > >>>>>> + /* When dirty tracking is enabled, allow only min supported pgsize */ > >>>>>> + if ((unmap->flags & VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) && > >>>>>> + (!iommu->dirty_page_tracking || (bitmap->pgsize != pgsize))) { > >>>>>> + ret = -EINVAL; > >>>>>> + goto unlock; > >>>>>> + } > >>>>>> > >>>>>> + WARN_ON((pgsize - 1) & PAGE_MASK); > >>>>>> +again: > >>>>>> /* > >>>>>> * vfio-iommu-type1 (v1) - User mappings were coalesced together to > >>>>>> * avoid tracking individual mappings. This means that the granularity > >>>>>> @@ -1066,6 +1078,7 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu, > >>>>>> ret = -EINVAL; > >>>>>> goto unlock; > >>>>>> } > >>>>>> + > >>>>>> dma = vfio_find_dma(iommu, unmap->iova + unmap->size - 1, 0); > >>>>>> if (dma && dma->iova + dma->size != unmap->iova + unmap->size) { > >>>>>> ret = -EINVAL; > >>>>>> @@ -1083,6 +1096,23 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu, > >>>>>> if (dma->task->mm != current->mm) > >>>>>> break; > >>>>>> > >>>>>> + if ((unmap->flags & VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) && > >>>>>> + (dma_last != dma)) { > >>>>>> + > >>>>>> + /* > >>>>>> + * mark all pages dirty if all pages are pinned and > >>>>>> + * mapped > >>>>>> + */ > >>>>>> + if (dma->iommu_mapped) > >>>>>> + bitmap_set(dma->bitmap, 0, > >>>>>> + dma->size >> pgshift); > >>>>> > >>>>> Nit, all the callers of update_user_bitmap() precede the call with this > >>>>> identical operation, we should probably push it into the function to do > >>>>> it. > >>>>> > >>>>>> + > >>>>>> + ret = update_user_bitmap(bitmap->data, dma, > >>>>>> + unmap->iova, pgsize); > >>>>>> + if (ret) > >>>>>> + break; > >>>>>> + } > >>>>>> + > >>>>> > >>>>> As noted last time, the above is just busy work if pfn_list is not > >>>>> already empty. The entire code block above should be moved to after > >>>>> the block below. Thanks, > >>>>> > >>>> > >>>> pfn_list will be empty for IOMMU backed devices where all pages are > >>>> pinned and mapped, > >>> > >>> Unless we're making use of the selective dirtying introduced in patch > >>> 8/8 or the container is shared with non-IOMMU backed mdevs. > >>> > >>>> but those should be reported as dirty. > >>> > >>> I'm confused how that justifies or requires this ordering. > >>> > >> > >> 1. non IOMMU mdev device: > >> - vendor driver pins pages > >> - pfn_list is not empty > >> - device dma or write to pinned pages > >> > >> 2. IOMMU backed mdev device or vfio device, but smart driver which pins > >> required pages > >> - vendor driver pins pages > >> - pfn_list is not empty > >> - device dma or write to pinned pages > >> > >> 3. IOMMU backed mdev device or vfio device, driver is not smart > >> - pages are pinned and mapped during attach > >> - pfn_list is empty > >> - device dma or write to any of pinned pages > >> > >> For case 3, here this function does bitmap_set(dma->bitmap), that is > >> mark all pages dirty and then accordingly copy bitmap to user buffer. > >> Copying dma->bitmap logic remains same. > > > > What dependency does case 3 have on pfn_list? Why does it matter if > > that bitmap_set() occurs before or after we've drained pfn_list? How > > do we know we're in case 3 before we've looked at pfn_list? > > > > If update_user_bitmap() is moved in if block like: > if (!RB_EMPTY_ROOT(&dma->pfn_list)) { > update_user_bitmap() > ... > } > > then update_user_bitmap() would never get called for case 3. > > >>>> So moved it > >>>> back above empty pfn_list check. > >>> > >>> Sorry, it still doesn't make any sense to me, and with no discussion I > >>> can't differentiate ignored comments from discarded comments. > >>> > >>> Pages in the pfn_list contribute to the dirty bitmap when they're > >>> pinned, we don't depend on pfn_list when reporting the dirty bitmap > >>> except for re-populating pfn_list dirtied pages after the bitmap has > >>> been cleared. We're unmapping the dma, so that's not the case here. > >>> Also since update_user_bitmap() shifts the bitmap in place now, any > >>> repetitive calls will give us incorrect results. > >> > >> Right, but this is unmapping and freeing vfio_dma > >> > >>> Therefore, as I see > >>> it, we _can_ take the branch below and when we do any work we've done > >>> above is not only wasted but may lead to incorrect data copied to > >>> the user if we shift dma->bitmap in place more than once. Please > >>> explain in more detail if you believe this is still correct. Thanks, > >>> > >> > >> In this case also bitmap copy to user happens once, (dma_last != dma) > >> takes care of making sure that its called only once. > > > > I did miss the dma_last check, so that prevents us from repeating this > > path, BUT we release iommu->lock if we enter the pfn_list !empty path. > > The moment we do that, we might unblock a vendor driver trying to pin > > or rw more pages. So the bitmap we've copied to the user might be stale > > and incorrect. I don't see why this is so contentious, what is the > > actual disadvantage to moving this until after we've drained pfn_list? > > The risks seem abundant to me. Thanks, > > > > Sorry if I misinterpreted earlier, are you proposing to move > update_user_bitmap() after this if block? > > if (!RB_EMPTY_ROOT(&dma->pfn_list)) { > ... > } > > I thought you are asking to move it in block. > That makes sense. I'll update the patch in send next version in some time. Yes, after not in. Thanks, Alex 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=-6.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 E8F5BC433E0 for ; Fri, 15 May 2020 15:49:25 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (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 A11BF20758 for ; Fri, 15 May 2020 15:49:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="MdE8He2L" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A11BF20758 Authentication-Results: mail.kernel.org; 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Fri, 15 May 2020 15:48:19 +0000 (UTC) Date: Fri, 15 May 2020 09:48:19 -0600 From: Alex Williamson To: Kirti Wankhede Subject: Re: [PATCH Kernel v20 6/8] vfio iommu: Update UNMAP_DMA ioctl to get dirty bitmap before unmap Message-ID: <20200515094819.58ce1756@w520.home> In-Reply-To: <41c5c3aa-6c03-def5-41e4-2803d0aa825c@nvidia.com> References: <1589488667-9683-1-git-send-email-kwankhede@nvidia.com> <1589488667-9683-7-git-send-email-kwankhede@nvidia.com> <20200514212706.036a336a@x1.home> <5256f488-2d11-eb0f-6980-eea23f4d3019@nvidia.com> <20200514234726.03c2e345@x1.home> <268ec129-a1cb-530a-c9b2-7ec53ddf4d17@nvidia.com> <20200515073135.2370a17d@x1.home> <41c5c3aa-6c03-def5-41e4-2803d0aa825c@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Received-SPF: pass client-ip=205.139.110.120; envelope-from=alex.williamson@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/14 23:27:07 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Zhengxiao.zx@Alibaba-inc.com, kevin.tian@intel.com, yi.l.liu@intel.com, cjia@nvidia.com, kvm@vger.kernel.org, eskultet@redhat.com, ziye.yang@intel.com, qemu-devel@nongnu.org, cohuck@redhat.com, shuangtai.tst@alibaba-inc.com, dgilbert@redhat.com, zhi.a.wang@intel.com, mlevitsk@redhat.com, pasic@linux.ibm.com, aik@ozlabs.ru, eauger@redhat.com, felipe@nutanix.com, jonathan.davies@nutanix.com, yan.y.zhao@intel.com, changpeng.liu@intel.com, Ken.Xue@amd.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Fri, 15 May 2020 21:00:32 +0530 Kirti Wankhede wrote: > On 5/15/2020 7:01 PM, Alex Williamson wrote: > > On Fri, 15 May 2020 12:17:03 +0530 > > Kirti Wankhede wrote: > > > >> On 5/15/2020 11:17 AM, Alex Williamson wrote: > >>> On Fri, 15 May 2020 09:46:43 +0530 > >>> Kirti Wankhede wrote: > >>> > >>>> On 5/15/2020 8:57 AM, Alex Williamson wrote: > >>>>> On Fri, 15 May 2020 02:07:45 +0530 > >>>>> Kirti Wankhede wrote: > >>>>> > >>>>>> DMA mapped pages, including those pinned by mdev vendor drivers, might > >>>>>> get unpinned and unmapped while migration is active and device is still > >>>>>> running. For example, in pre-copy phase while guest driver could access > >>>>>> those pages, host device or vendor driver can dirty these mapped pages. > >>>>>> Such pages should be marked dirty so as to maintain memory consistency > >>>>>> for a user making use of dirty page tracking. > >>>>>> > >>>>>> To get bitmap during unmap, user should allocate memory for bitmap, set > >>>>>> it all zeros, set size of allocated memory, set page size to be > >>>>>> considered for bitmap and set flag VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP. > >>>>>> > >>>>>> Signed-off-by: Kirti Wankhede > >>>>>> Reviewed-by: Neo Jia > >>>>>> --- > >>>>>> drivers/vfio/vfio_iommu_type1.c | 77 ++++++++++++++++++++++++++++++++++------- > >>>>>> include/uapi/linux/vfio.h | 10 ++++++ > >>>>>> 2 files changed, 75 insertions(+), 12 deletions(-) > >>>>>> > >>>>>> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c > >>>>>> index b76d3b14abfd..a1dc57bcece5 100644 > >>>>>> --- a/drivers/vfio/vfio_iommu_type1.c > >>>>>> +++ b/drivers/vfio/vfio_iommu_type1.c > >>>>>> @@ -195,11 +195,15 @@ static void vfio_unlink_dma(struct vfio_iommu *iommu, struct vfio_dma *old) > >>>>>> static int vfio_dma_bitmap_alloc(struct vfio_dma *dma, size_t pgsize) > >>>>>> { > >>>>>> uint64_t npages = dma->size / pgsize; > >>>>>> + size_t bitmap_size; > >>>>>> > >>>>>> if (npages > DIRTY_BITMAP_PAGES_MAX) > >>>>>> return -EINVAL; > >>>>>> > >>>>>> - dma->bitmap = kvzalloc(DIRTY_BITMAP_BYTES(npages), GFP_KERNEL); > >>>>>> + /* Allocate extra 64 bits which are used for bitmap manipulation */ > >>>>>> + bitmap_size = DIRTY_BITMAP_BYTES(npages) + sizeof(u64); > >>>>>> + > >>>>>> + dma->bitmap = kvzalloc(bitmap_size, GFP_KERNEL); > >>>>>> if (!dma->bitmap) > >>>>>> return -ENOMEM; > >>>>>> > >>>>>> @@ -999,23 +1003,25 @@ static int verify_bitmap_size(uint64_t npages, uint64_t bitmap_size) > >>>>>> } > >>>>>> > >>>>>> static int vfio_dma_do_unmap(struct vfio_iommu *iommu, > >>>>>> - struct vfio_iommu_type1_dma_unmap *unmap) > >>>>>> + struct vfio_iommu_type1_dma_unmap *unmap, > >>>>>> + struct vfio_bitmap *bitmap) > >>>>>> { > >>>>>> - uint64_t mask; > >>>>>> struct vfio_dma *dma, *dma_last = NULL; > >>>>>> - size_t unmapped = 0; > >>>>>> + size_t unmapped = 0, pgsize; > >>>>>> int ret = 0, retries = 0; > >>>>>> + unsigned long pgshift; > >>>>>> > >>>>>> mutex_lock(&iommu->lock); > >>>>>> > >>>>>> - mask = ((uint64_t)1 << __ffs(iommu->pgsize_bitmap)) - 1; > >>>>>> + pgshift = __ffs(iommu->pgsize_bitmap); > >>>>>> + pgsize = (size_t)1 << pgshift; > >>>>>> > >>>>>> - if (unmap->iova & mask) { > >>>>>> + if (unmap->iova & (pgsize - 1)) { > >>>>>> ret = -EINVAL; > >>>>>> goto unlock; > >>>>>> } > >>>>>> > >>>>>> - if (!unmap->size || unmap->size & mask) { > >>>>>> + if (!unmap->size || unmap->size & (pgsize - 1)) { > >>>>>> ret = -EINVAL; > >>>>>> goto unlock; > >>>>>> } > >>>>>> @@ -1026,9 +1032,15 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu, > >>>>>> goto unlock; > >>>>>> } > >>>>>> > >>>>>> - WARN_ON(mask & PAGE_MASK); > >>>>>> -again: > >>>>>> + /* When dirty tracking is enabled, allow only min supported pgsize */ > >>>>>> + if ((unmap->flags & VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) && > >>>>>> + (!iommu->dirty_page_tracking || (bitmap->pgsize != pgsize))) { > >>>>>> + ret = -EINVAL; > >>>>>> + goto unlock; > >>>>>> + } > >>>>>> > >>>>>> + WARN_ON((pgsize - 1) & PAGE_MASK); > >>>>>> +again: > >>>>>> /* > >>>>>> * vfio-iommu-type1 (v1) - User mappings were coalesced together to > >>>>>> * avoid tracking individual mappings. This means that the granularity > >>>>>> @@ -1066,6 +1078,7 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu, > >>>>>> ret = -EINVAL; > >>>>>> goto unlock; > >>>>>> } > >>>>>> + > >>>>>> dma = vfio_find_dma(iommu, unmap->iova + unmap->size - 1, 0); > >>>>>> if (dma && dma->iova + dma->size != unmap->iova + unmap->size) { > >>>>>> ret = -EINVAL; > >>>>>> @@ -1083,6 +1096,23 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu, > >>>>>> if (dma->task->mm != current->mm) > >>>>>> break; > >>>>>> > >>>>>> + if ((unmap->flags & VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) && > >>>>>> + (dma_last != dma)) { > >>>>>> + > >>>>>> + /* > >>>>>> + * mark all pages dirty if all pages are pinned and > >>>>>> + * mapped > >>>>>> + */ > >>>>>> + if (dma->iommu_mapped) > >>>>>> + bitmap_set(dma->bitmap, 0, > >>>>>> + dma->size >> pgshift); > >>>>> > >>>>> Nit, all the callers of update_user_bitmap() precede the call with this > >>>>> identical operation, we should probably push it into the function to do > >>>>> it. > >>>>> > >>>>>> + > >>>>>> + ret = update_user_bitmap(bitmap->data, dma, > >>>>>> + unmap->iova, pgsize); > >>>>>> + if (ret) > >>>>>> + break; > >>>>>> + } > >>>>>> + > >>>>> > >>>>> As noted last time, the above is just busy work if pfn_list is not > >>>>> already empty. The entire code block above should be moved to after > >>>>> the block below. Thanks, > >>>>> > >>>> > >>>> pfn_list will be empty for IOMMU backed devices where all pages are > >>>> pinned and mapped, > >>> > >>> Unless we're making use of the selective dirtying introduced in patch > >>> 8/8 or the container is shared with non-IOMMU backed mdevs. > >>> > >>>> but those should be reported as dirty. > >>> > >>> I'm confused how that justifies or requires this ordering. > >>> > >> > >> 1. non IOMMU mdev device: > >> - vendor driver pins pages > >> - pfn_list is not empty > >> - device dma or write to pinned pages > >> > >> 2. IOMMU backed mdev device or vfio device, but smart driver which pins > >> required pages > >> - vendor driver pins pages > >> - pfn_list is not empty > >> - device dma or write to pinned pages > >> > >> 3. IOMMU backed mdev device or vfio device, driver is not smart > >> - pages are pinned and mapped during attach > >> - pfn_list is empty > >> - device dma or write to any of pinned pages > >> > >> For case 3, here this function does bitmap_set(dma->bitmap), that is > >> mark all pages dirty and then accordingly copy bitmap to user buffer. > >> Copying dma->bitmap logic remains same. > > > > What dependency does case 3 have on pfn_list? Why does it matter if > > that bitmap_set() occurs before or after we've drained pfn_list? How > > do we know we're in case 3 before we've looked at pfn_list? > > > > If update_user_bitmap() is moved in if block like: > if (!RB_EMPTY_ROOT(&dma->pfn_list)) { > update_user_bitmap() > ... > } > > then update_user_bitmap() would never get called for case 3. > > >>>> So moved it > >>>> back above empty pfn_list check. > >>> > >>> Sorry, it still doesn't make any sense to me, and with no discussion I > >>> can't differentiate ignored comments from discarded comments. > >>> > >>> Pages in the pfn_list contribute to the dirty bitmap when they're > >>> pinned, we don't depend on pfn_list when reporting the dirty bitmap > >>> except for re-populating pfn_list dirtied pages after the bitmap has > >>> been cleared. We're unmapping the dma, so that's not the case here. > >>> Also since update_user_bitmap() shifts the bitmap in place now, any > >>> repetitive calls will give us incorrect results. > >> > >> Right, but this is unmapping and freeing vfio_dma > >> > >>> Therefore, as I see > >>> it, we _can_ take the branch below and when we do any work we've done > >>> above is not only wasted but may lead to incorrect data copied to > >>> the user if we shift dma->bitmap in place more than once. Please > >>> explain in more detail if you believe this is still correct. Thanks, > >>> > >> > >> In this case also bitmap copy to user happens once, (dma_last != dma) > >> takes care of making sure that its called only once. > > > > I did miss the dma_last check, so that prevents us from repeating this > > path, BUT we release iommu->lock if we enter the pfn_list !empty path. > > The moment we do that, we might unblock a vendor driver trying to pin > > or rw more pages. So the bitmap we've copied to the user might be stale > > and incorrect. I don't see why this is so contentious, what is the > > actual disadvantage to moving this until after we've drained pfn_list? > > The risks seem abundant to me. Thanks, > > > > Sorry if I misinterpreted earlier, are you proposing to move > update_user_bitmap() after this if block? > > if (!RB_EMPTY_ROOT(&dma->pfn_list)) { > ... > } > > I thought you are asking to move it in block. > That makes sense. I'll update the patch in send next version in some time. Yes, after not in. Thanks, Alex