From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f72.google.com (mail-pg0-f72.google.com [74.125.83.72]) by kanga.kvack.org (Postfix) with ESMTP id D448C6B0008 for ; Thu, 22 Mar 2018 00:52:39 -0400 (EDT) Received: by mail-pg0-f72.google.com with SMTP id v14so3537314pgq.11 for ; Wed, 21 Mar 2018 21:52:39 -0700 (PDT) Received: from out30-131.freemail.mail.aliyun.com (out30-131.freemail.mail.aliyun.com. [115.124.30.131]) by mx.google.com with ESMTPS id 79si4273932pfh.118.2018.03.21.21.52.37 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 21 Mar 2018 21:52:38 -0700 (PDT) From: "Jason Cai (Xiang Feng)" Subject: [PATCH] vfio iommu type1: improve memory pinning process for raw PFN mapping Date: Thu, 22 Mar 2018 12:52:16 +0800 Message-Id: <20180322045216.22220-1-jason.cai@linux.alibaba.com> Sender: owner-linux-mm@kvack.org List-ID: To: alex.williamson@redhat.com, pbonzini@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: gnehzuil@linux.alibaba.com, jason.cai@linux.alibaba.com 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 = 0; long ret, pinned = 0, lock_acct = 0; - bool rsvd; dma_addr_t iova = 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 = find_vma_intersection(current->mm, vaddr, vaddr + 1); + pinned = min(npage, (long)vma_pages(vma)); + up_read(¤t->mm->mmap_sem); + return pinned; + } + pinned++; - rsvd = 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 != *pfn_base + pinned || - rsvd != is_invalid_reserved_pfn(pfn)) { + if (pfn != *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 = *pfn_base ; pinned ; pfn++, pinned--) - put_pfn(pfn, dma->prot); - } + for (pfn = *pfn_base ; pinned ; pfn++, pinned--) + put_pfn(pfn, dma->prot); return ret; } -- 2.13.6