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=-8.4 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,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 B816EC4332B for ; Thu, 19 Mar 2020 14:52:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6E7B620B1F for ; Thu, 19 Mar 2020 14:52:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="bKrP9Zy8" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727473AbgCSOw4 (ORCPT ); Thu, 19 Mar 2020 10:52:56 -0400 Received: from hqnvemgate24.nvidia.com ([216.228.121.143]:19814 "EHLO hqnvemgate24.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727095AbgCSOw4 (ORCPT ); Thu, 19 Mar 2020 10:52:56 -0400 Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate24.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Thu, 19 Mar 2020 07:51:16 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Thu, 19 Mar 2020 07:52:54 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Thu, 19 Mar 2020 07:52:54 -0700 Received: from [10.40.102.54] (10.124.1.5) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Thu, 19 Mar 2020 14:52:46 +0000 Subject: Re: [PATCH v14 Kernel 4/7] vfio iommu: Implementation of ioctl for dirty pages tracking. To: Alex Williamson CC: , , , , , , , , , , , , , , , , , , , , References: <1584560474-19946-1-git-send-email-kwankhede@nvidia.com> <1584560474-19946-5-git-send-email-kwankhede@nvidia.com> <20200318214500.1a0cb985@w520.home> X-Nvconfidentiality: public From: Kirti Wankhede Message-ID: Date: Thu, 19 Mar 2020 20:22:41 +0530 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200318214500.1a0cb985@w520.home> X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL101.nvidia.com (172.20.187.10) To HQMAIL107.nvidia.com (172.20.187.13) Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1584629476; bh=dDxfFpVv1wOTY5SS5GpKXoCSC88h6bMeE0jAKqP6744=; h=X-PGP-Universal:Subject:To:CC:References:X-Nvconfidentiality:From: Message-ID:Date:User-Agent:MIME-Version:In-Reply-To: X-Originating-IP:X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=bKrP9Zy85XuwpvgIo7bcxjidMhWZukx/nM8hzy7ZqwzfwhOl0ckuu9zF7giYugdbY j9esTsmLuWwggxnSJXKuBI6vC3i+FykFh+l+wWdq1H9CrDwgNaDBZa/SiC31qEV74h qRjf8Q3oi7S74NjRyUh2Juy2NU3m7BTa84h4ZVGUuv7D9NpQRaE6DsDxOr0r5DJ6l5 kn/XBUFpu/gGw5YsRI0tU5czrGLbH9It+HdSBf3uCYLXuf8Mi+AhczOTzQeUyFKF7l 9lUhPUGtjrpSE6ZevS2jncfJB45TK+bHasC9o8ktwAuJOl5sEivkYyF7c/vhanLCFg tfEgYPtb8JIKg== Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 3/19/2020 9:15 AM, Alex Williamson wrote: > On Thu, 19 Mar 2020 01:11:11 +0530 > Kirti Wankhede wrote: > >> VFIO_IOMMU_DIRTY_PAGES ioctl performs three operations: >> - Start dirty pages tracking while migration is active >> - Stop dirty pages tracking. >> - Get dirty pages bitmap. Its user space application's responsibility to >> copy content of dirty pages from source to destination during migration. >> >> To prevent DoS attack, memory for bitmap is allocated per vfio_dma >> structure. Bitmap size is calculated considering smallest supported page >> size. Bitmap is allocated for all vfio_dmas when dirty logging is enabled >> >> Bitmap is populated for already pinned pages when bitmap is allocated for >> a vfio_dma with the smallest supported page size. Update bitmap from >> pinning functions when tracking is enabled. When user application queries >> bitmap, check if requested page size is same as page size used to >> populated bitmap. If it is equal, copy bitmap, but if not equal, return >> error. >> >> Signed-off-by: Kirti Wankhede >> Reviewed-by: Neo Jia >> --- >> drivers/vfio/vfio_iommu_type1.c | 205 +++++++++++++++++++++++++++++++++++++++- >> 1 file changed, 203 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c >> index 70aeab921d0f..d6417fb02174 100644 >> --- a/drivers/vfio/vfio_iommu_type1.c >> +++ b/drivers/vfio/vfio_iommu_type1.c >> @@ -71,6 +71,7 @@ struct vfio_iommu { >> unsigned int dma_avail; >> bool v2; >> bool nesting; >> + bool dirty_page_tracking; >> }; >> >> struct vfio_domain { >> @@ -91,6 +92,7 @@ struct vfio_dma { >> bool lock_cap; /* capable(CAP_IPC_LOCK) */ >> struct task_struct *task; >> struct rb_root pfn_list; /* Ex-user pinned pfn list */ >> + unsigned long *bitmap; > > We've made the bitmap a width invariant u64 else, should be here as > well. > >> }; >> >> struct vfio_group { >> @@ -125,7 +127,10 @@ struct vfio_regions { >> #define IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu) \ >> (!list_empty(&iommu->domain_list)) >> >> +#define DIRTY_BITMAP_BYTES(n) (ALIGN(n, BITS_PER_TYPE(u64)) / BITS_PER_BYTE) >> + >> static int put_pfn(unsigned long pfn, int prot); >> +static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu); >> >> /* >> * This code handles mapping and unmapping of user data buffers >> @@ -175,6 +180,55 @@ static void vfio_unlink_dma(struct vfio_iommu *iommu, struct vfio_dma *old) >> rb_erase(&old->node, &iommu->dma_list); >> } >> >> +static int vfio_dma_bitmap_alloc(struct vfio_iommu *iommu, uint64_t pgsize) >> +{ >> + struct rb_node *n = rb_first(&iommu->dma_list); >> + >> + for (; n; n = rb_next(n)) { >> + struct vfio_dma *dma = rb_entry(n, struct vfio_dma, node); >> + struct rb_node *p; >> + unsigned long npages = dma->size / pgsize; >> + >> + dma->bitmap = kvzalloc(DIRTY_BITMAP_BYTES(npages), GFP_KERNEL); >> + if (!dma->bitmap) { >> + struct rb_node *p = rb_prev(n); >> + >> + for (; p; p = rb_prev(p)) { >> + struct vfio_dma *dma = rb_entry(n, >> + struct vfio_dma, node); >> + >> + kfree(dma->bitmap); >> + dma->bitmap = NULL; >> + } >> + return -ENOMEM; >> + } >> + >> + if (RB_EMPTY_ROOT(&dma->pfn_list)) >> + continue; >> + >> + for (p = rb_first(&dma->pfn_list); p; p = rb_next(p)) { >> + struct vfio_pfn *vpfn = rb_entry(p, struct vfio_pfn, >> + node); >> + >> + bitmap_set(dma->bitmap, >> + (vpfn->iova - dma->iova) / pgsize, 1); >> + } >> + } >> + return 0; >> +} >> + >> +static void vfio_dma_bitmap_free(struct vfio_iommu *iommu) >> +{ >> + struct rb_node *n = rb_first(&iommu->dma_list); >> + >> + for (; n; n = rb_next(n)) { >> + struct vfio_dma *dma = rb_entry(n, struct vfio_dma, node); >> + >> + kfree(dma->bitmap); >> + dma->bitmap = NULL; >> + } >> +} >> + >> /* >> * Helper Functions for host iova-pfn list >> */ >> @@ -567,6 +621,14 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data, >> vfio_unpin_page_external(dma, iova, do_accounting); >> goto pin_unwind; >> } >> + >> + if (iommu->dirty_page_tracking) { >> + unsigned long pgshift = >> + __ffs(vfio_pgsize_bitmap(iommu)); >> + >> + bitmap_set(dma->bitmap, >> + (vpfn->iova - dma->iova) >> pgshift, 1); >> + } >> } >> >> ret = i; >> @@ -801,6 +863,7 @@ static void vfio_remove_dma(struct vfio_iommu *iommu, struct vfio_dma *dma) >> vfio_unmap_unpin(iommu, dma, true); >> vfio_unlink_dma(iommu, dma); >> put_task_struct(dma->task); >> + kfree(dma->bitmap); >> kfree(dma); >> iommu->dma_avail++; >> } >> @@ -831,6 +894,50 @@ static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu) >> return bitmap; >> } >> >> +static int vfio_iova_dirty_bitmap(struct vfio_iommu *iommu, dma_addr_t iova, >> + size_t size, uint64_t pgsize, >> + unsigned char __user *bitmap) > > And here, why do callers cast to an unsigned char pointer when we're > going to cast to a void pointer anyway? Should be a u64 __user pointer. > >> +{ >> + struct vfio_dma *dma; >> + unsigned long pgshift = __ffs(pgsize); >> + unsigned int npages, bitmap_size; >> + >> + dma = vfio_find_dma(iommu, iova, 1); >> + >> + if (!dma) >> + return -EINVAL; >> + >> + if (dma->iova != iova || dma->size != size) >> + return -EINVAL; >> + >> + npages = dma->size >> pgshift; >> + bitmap_size = DIRTY_BITMAP_BYTES(npages); >> + >> + /* mark all pages dirty if all pages are pinned and mapped. */ >> + if (dma->iommu_mapped) >> + bitmap_set(dma->bitmap, 0, npages); >> + >> + if (copy_to_user((void __user *)bitmap, dma->bitmap, bitmap_size)) >> + return -EFAULT; >> + >> + return 0; >> +} >> + >> +static int verify_bitmap_size(uint64_t npages, uint64_t bitmap_size) >> +{ >> + uint64_t bsize; >> + >> + if (!npages || !bitmap_size || bitmap_size > UINT_MAX) > > As commented previously, how do we derive this UINT_MAX limitation? > Sorry, I missed that earlier > UINT_MAX seems arbitrary, is this specified in our API? The size of a > vfio_dma is limited to what the user is able to pin, and therefore > their locked memory limit, but do we have an explicit limit elsewhere > that results in this limit here. I think a 4GB bitmap would track > something like 2^47 bytes of memory, that's pretty excessive, but still > an arbitrary limit. There has to be some upper limit check. In core KVM, in virt/kvm/kvm_main.c there is max number of pages check: if (new.npages > KVM_MEM_MAX_NR_PAGES) Where /* * Some of the bitops functions do not support too long bitmaps. * This number must be determined not to exceed such limits. */ #define KVM_MEM_MAX_NR_PAGES ((1UL << 31) - 1) Though I don't know which bitops functions do not support long bitmaps. Something similar as above can be done or same as you also mentioned of 4GB bitmap limit? that is U32_MAX instead of UINT_MAX? >> + return -EINVAL; >> + >> + bsize = DIRTY_BITMAP_BYTES(npages); >> + >> + if (bitmap_size < bsize) >> + return -EINVAL; >> + >> + return 0; >> +} >> + >> static int vfio_dma_do_unmap(struct vfio_iommu *iommu, >> struct vfio_iommu_type1_dma_unmap *unmap) >> { > > We didn't address that vfio_dma_do_map() needs to kvzalloc a bitmap for > any new vfio_dma created while iommu->dirty_page_tracking = true. > Good point. Adding it. Thanks, Kirti >> @@ -2278,6 +2385,93 @@ static long vfio_iommu_type1_ioctl(void *iommu_data, >> >> return copy_to_user((void __user *)arg, &unmap, minsz) ? >> -EFAULT : 0; >> + } else if (cmd == VFIO_IOMMU_DIRTY_PAGES) { >> + struct vfio_iommu_type1_dirty_bitmap dirty; >> + uint32_t mask = VFIO_IOMMU_DIRTY_PAGES_FLAG_START | >> + VFIO_IOMMU_DIRTY_PAGES_FLAG_STOP | >> + VFIO_IOMMU_DIRTY_PAGES_FLAG_GET_BITMAP; >> + int ret = 0; >> + >> + if (!iommu->v2) >> + return -EACCES; >> + >> + minsz = offsetofend(struct vfio_iommu_type1_dirty_bitmap, >> + flags); >> + >> + if (copy_from_user(&dirty, (void __user *)arg, minsz)) >> + return -EFAULT; >> + >> + if (dirty.argsz < minsz || dirty.flags & ~mask) >> + return -EINVAL; >> + >> + /* only one flag should be set at a time */ >> + if (__ffs(dirty.flags) != __fls(dirty.flags)) >> + return -EINVAL; >> + >> + if (dirty.flags & VFIO_IOMMU_DIRTY_PAGES_FLAG_START) { >> + uint64_t pgsize = 1 << __ffs(vfio_pgsize_bitmap(iommu)); >> + >> + mutex_lock(&iommu->lock); >> + if (!iommu->dirty_page_tracking) { >> + ret = vfio_dma_bitmap_alloc(iommu, pgsize); >> + if (!ret) >> + iommu->dirty_page_tracking = true; >> + } >> + mutex_unlock(&iommu->lock); >> + return ret; >> + } else if (dirty.flags & VFIO_IOMMU_DIRTY_PAGES_FLAG_STOP) { >> + mutex_lock(&iommu->lock); >> + if (iommu->dirty_page_tracking) { >> + iommu->dirty_page_tracking = false; >> + vfio_dma_bitmap_free(iommu); >> + } >> + mutex_unlock(&iommu->lock); >> + return 0; >> + } else if (dirty.flags & >> + VFIO_IOMMU_DIRTY_PAGES_FLAG_GET_BITMAP) { >> + struct vfio_iommu_type1_dirty_bitmap_get range; >> + unsigned long pgshift; >> + size_t data_size = dirty.argsz - minsz; >> + uint64_t iommu_pgsize = >> + 1 << __ffs(vfio_pgsize_bitmap(iommu)); >> + >> + if (!data_size || data_size < sizeof(range)) >> + return -EINVAL; >> + >> + if (copy_from_user(&range, (void __user *)(arg + minsz), >> + sizeof(range))) >> + return -EFAULT; >> + >> + /* allow only min supported pgsize */ >> + if (range.bitmap.pgsize != iommu_pgsize) >> + return -EINVAL; >> + if (range.iova & (iommu_pgsize - 1)) >> + return -EINVAL; >> + if (!range.size || range.size & (iommu_pgsize - 1)) >> + return -EINVAL; >> + if (range.iova + range.size < range.iova) >> + return -EINVAL; >> + if (!access_ok((void __user *)range.bitmap.data, >> + range.bitmap.size)) >> + return -EINVAL; >> + >> + pgshift = __ffs(range.bitmap.pgsize); >> + ret = verify_bitmap_size(range.size >> pgshift, >> + range.bitmap.size); >> + if (ret) >> + return ret; >> + >> + mutex_lock(&iommu->lock); >> + if (iommu->dirty_page_tracking) >> + ret = vfio_iova_dirty_bitmap(iommu, range.iova, >> + range.size, range.bitmap.pgsize, >> + (unsigned char __user *)range.bitmap.data); >> + else >> + ret = -EINVAL; >> + mutex_unlock(&iommu->lock); >> + >> + return ret; >> + } >> } >> >> return -ENOTTY; >> @@ -2345,10 +2539,17 @@ static int vfio_iommu_type1_dma_rw_chunk(struct vfio_iommu *iommu, >> >> vaddr = dma->vaddr + offset; >> >> - if (write) >> + if (write) { >> *copied = __copy_to_user((void __user *)vaddr, data, >> count) ? 0 : count; >> - else >> + if (*copied && iommu->dirty_page_tracking) { >> + unsigned long pgshift = >> + __ffs(vfio_pgsize_bitmap(iommu)); >> + >> + bitmap_set(dma->bitmap, offset >> pgshift, >> + *copied >> pgshift); >> + } >> + } else > > Great, thanks for adding this! > >> *copied = __copy_from_user(data, (void __user *)vaddr, >> count) ? 0 : count; >> if (kthread) >