From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Jason Cai (Xiang Feng)" Subject: [RFC v2] vfio iommu type1: improve memory pinning process for raw PFN mapping Date: Sat, 3 Mar 2018 20:10:33 +0800 Message-ID: <25959294-E232-43EB-9CE2-E558A8D62F57@linux.alibaba.com> References: <7090CB2E-8D63-44B1-A739-932FFA649BC9@linux.alibaba.com> <20180226121930.5e1f6300@w520.home> Mime-Version: 1.0 (Mac OS X Mail 10.2 \(3259\)) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8BIT Cc: pbonzini@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, gnehzuil@linux.alibaba.com To: Alex Williamson Return-path: In-Reply-To: <20180226121930.5e1f6300@w520.home> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org 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. Thus, it can significantly improve VM's boot up time when passing through devices via VFIO. 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 e30e29ae4819..82ccfa350315 100644 --- a/drivers/vfio/vfio_iommu_type1.c +++ b/drivers/vfio/vfio_iommu_type1.c @@ -385,7 +385,6 @@ 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 */ @@ -396,14 +395,22 @@ 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__, @@ -423,13 +430,12 @@ 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); @@ -447,10 +453,8 @@ 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