From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl0-f70.google.com (mail-pl0-f70.google.com [209.85.160.70]) by kanga.kvack.org (Postfix) with ESMTP id 2D4A06B0003 for ; Sun, 18 Mar 2018 22:30:29 -0400 (EDT) Received: by mail-pl0-f70.google.com with SMTP id az5-v6so9549624plb.14 for ; Sun, 18 Mar 2018 19:30:29 -0700 (PDT) Received: from out30-133.freemail.mail.aliyun.com (out30-133.freemail.mail.aliyun.com. [115.124.30.133]) by mx.google.com with ESMTPS id p26-v6si11099741pli.534.2018.03.18.19.30.26 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 18 Mar 2018 19:30:27 -0700 (PDT) From: "Jason Cai (Xiang Feng)" Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Mime-Version: 1.0 (Mac OS X Mail 10.2 \(3259\)) Subject: [PATCH] vfio iommu type1: improve memory pinning process for raw PFN mapping Message-Id: <7F93BB33-4ABF-468F-8814-78DE9D23FA08@linux.alibaba.com> Date: Mon, 19 Mar 2018 10:30:24 +0800 Sender: owner-linux-mm@kvack.org List-ID: To: Alex Williamson , pbonzini@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: gnehzuil@linux.alibaba.com, "Jason Cai (Xiang Feng)" When using vfio to pass through a PCIe device (e.g. a GPU card) that has a huge BAR (e.g. 16GB), a lot of cycles are wasted on memory pinning because PFNs of PCI BAR are not backed by struct page, and the corresponding VMA has flag VM_PFNMAP. With this change, when pinning a region which is a raw PFN mapping, it can skip unnecessary user memory pinning process, and thus, can significantly improve VM's boot up time when passing through devices via VFIO. In my test on a Xeon E5 2.6GHz, the time mapping a 16GB BAR was reduced from about 0.4s to 1.5us. Signed-off-by: Jason Cai (Xiang Feng) --- drivers/vfio/vfio_iommu_type1.c | 24 ++++++++++++++---------- 1 file changed, 14 insertions(+), 10 deletions(-) diff --git a/drivers/vfio/vfio_iommu_type1.c = b/drivers/vfio/vfio_iommu_type1.c index 45657e2b1ff7..0658f35318b8 100644 --- a/drivers/vfio/vfio_iommu_type1.c +++ b/drivers/vfio/vfio_iommu_type1.c @@ -397,7 +397,6 @@ static long vfio_pin_pages_remote(struct vfio_dma = *dma, unsigned long vaddr, { unsigned long pfn =3D 0; long ret, pinned =3D 0, lock_acct =3D 0; - bool rsvd; dma_addr_t iova =3D vaddr - dma->vaddr + dma->iova; /* This code path is only user initiated */ @@ -408,14 +407,22 @@ static long vfio_pin_pages_remote(struct vfio_dma = *dma, unsigned long vaddr, if (ret) return ret; + if (is_invalid_reserved_pfn(*pfn_base)) { + struct vm_area_struct *vma; + down_read(¤t->mm->mmap_sem); + vma =3D find_vma_intersection(current->mm, vaddr, vaddr = + 1); + pinned =3D min(npage, (long)vma_pages(vma)); + up_read(¤t->mm->mmap_sem); + return pinned; + } + pinned++; - rsvd =3D is_invalid_reserved_pfn(*pfn_base); /* * Reserved pages aren't counted against the user, externally = pinned * pages are already counted against the user. */ - if (!rsvd && !vfio_find_vpfn(dma, iova)) { + if (!vfio_find_vpfn(dma, iova)) { if (!lock_cap && current->mm->locked_vm + 1 > limit) { put_pfn(*pfn_base, dma->prot); pr_warn("%s: RLIMIT_MEMLOCK (%ld) exceeded\n", = __func__, @@ -435,13 +442,12 @@ static long vfio_pin_pages_remote(struct vfio_dma = *dma, unsigned long vaddr, if (ret) break; - if (pfn !=3D *pfn_base + pinned || - rsvd !=3D is_invalid_reserved_pfn(pfn)) { + if (pfn !=3D *pfn_base + pinned) { put_pfn(pfn, dma->prot); break; } - if (!rsvd && !vfio_find_vpfn(dma, iova)) { + if (!vfio_find_vpfn(dma, iova)) { if (!lock_cap && current->mm->locked_vm + lock_acct + 1 > = limit) { put_pfn(pfn, dma->prot); @@ -459,10 +465,8 @@ static long vfio_pin_pages_remote(struct vfio_dma = *dma, unsigned long vaddr, unpin_out: if (ret) { - if (!rsvd) { - for (pfn =3D *pfn_base ; pinned ; pfn++, = pinned--) - put_pfn(pfn, dma->prot); - } + for (pfn =3D *pfn_base ; pinned ; pfn++, pinned--) + put_pfn(pfn, dma->prot); return ret; } -- 2.13.6