From: Alex Williamson <alex.williamson@redhat.com>
To: Yan Zhao <yan.y.zhao@intel.com>
Cc: Kirti Wankhede <kwankhede@nvidia.com>,
"cjia@nvidia.com" <cjia@nvidia.com>,
"Tian, Kevin" <kevin.tian@intel.com>,
"Yang, Ziye" <ziye.yang@intel.com>,
"Liu, Changpeng" <changpeng.liu@intel.com>,
"Liu, Yi L" <yi.l.liu@intel.com>,
"mlevitsk@redhat.com" <mlevitsk@redhat.com>,
"eskultet@redhat.com" <eskultet@redhat.com>,
"cohuck@redhat.com" <cohuck@redhat.com>,
"dgilbert@redhat.com" <dgilbert@redhat.com>,
"jonathan.davies@nutanix.com" <jonathan.davies@nutanix.com>,
"eauger@redhat.com" <eauger@redhat.com>,
"aik@ozlabs.ru" <aik@ozlabs.ru>,
"pasic@linux.ibm.com" <pasic@linux.ibm.com>,
"felipe@nutanix.com" <felipe@nutanix.com>,
"Zhengxiao.zx@Alibaba-inc.com" <Zhengxiao.zx@Alibaba-inc.com>,
"shuangtai.tst@alibaba-inc.com" <shuangtai.tst@alibaba-inc.com>,
"Ken.Xue@amd.com" <Ken.Xue@amd.com>,
"Wang, Zhi A" <zhi.a.wang@intel.com>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>
Subject: Re: [PATCH v14 Kernel 4/7] vfio iommu: Implementation of ioctl for dirty pages tracking.
Date: Wed, 18 Mar 2020 22:40:53 -0600 [thread overview]
Message-ID: <20200318224053.3651c818@w520.home> (raw)
In-Reply-To: <20200319041533.GE4641@joy-OptiPlex-7040>
On Thu, 19 Mar 2020 00:15:33 -0400
Yan Zhao <yan.y.zhao@intel.com> wrote:
> On Thu, Mar 19, 2020 at 12:01:00PM +0800, Alex Williamson wrote:
> > On Wed, 18 Mar 2020 23:06:39 -0400
> > Yan Zhao <yan.y.zhao@intel.com> wrote:
> >
> > > On Thu, Mar 19, 2020 at 03:41:11AM +0800, 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 <kwankhede@nvidia.com>
> > > > Reviewed-by: Neo Jia <cjia@nvidia.com>
> > > > ---
> > > > 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;
> > > > };
> > > >
> > > > 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)
> > > > +{
> > > > + 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;
> > > > +
> > > looks this size is passed from user. how can it ensure size always
> > > equals to dma->size ?
> > >
> > > shouldn't we iterate dma tree to look for dirty for whole range if a
> > > single dma cannot meet them all?
> >
> > Please see the discussion on v12[1], the problem is with the alignment
> > of DMA mapped regions versus the bitmap. A DMA mapping only requires
> > page alignment, so for example imagine a user requests the bitmap from
> > page zero to 4GB, but we have a DMA mapping starting at 4KB. We can't
> > efficiently copy the bitmap tracked by the vfio_dma structure to the
> > user buffer when it's shifted by 1 bit. Adjacent mappings can also
> > make for a very complicated implementation. In the discussion linked
> > we decided to compromise on a more simple implementation that requires
> > the user to ask for a bitmap which exactly matches a single DMA
> > mapping, which Kirti indicates is what we require to support QEMU.
> > Later in the series, the unmap operation also makes this requirement
> > when used with the flags to retrieve the dirty bitmap. Thanks,
> >
>
> so, what about for vIOMMU enabling case?
> if IOVAs are mapped per page, then there's a log_sync in qemu,
> it's supposed for range from 0-U64MAX, qemu has to find out which
> ones are mapped and cut them into pages before calling this IOCTL?
> And what if those IOVAs are mapped for len more than one page?
Good question. Kirti?
> > [1] https://lore.kernel.org/kvm/20200218215330.5bc8fc6a@w520.home/
> >
> > > > + 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)
> > > > + 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)
> > > > {
> > > > @@ -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
> > > > *copied = __copy_from_user(data, (void __user *)vaddr,
> > > > count) ? 0 : count;
> > > > if (kthread)
> > > > --
> > > > 2.7.0
> > > >
> > >
> >
>
next prev parent reply other threads:[~2020-03-19 4:41 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-18 19:41 [PATCH v14 Kernel 0/7] KABIs to support migration for VFIO devices Kirti Wankhede
2020-03-18 19:41 ` [PATCH v14 Kernel 1/7] vfio: KABI for migration interface for device state Kirti Wankhede
2020-03-19 1:17 ` Yan Zhao
2020-03-19 3:49 ` Alex Williamson
2020-03-19 5:05 ` Yan Zhao
2020-03-19 13:09 ` Alex Williamson
2020-03-20 1:30 ` Yan Zhao
2020-03-20 2:34 ` Alex Williamson
2020-03-20 3:06 ` Yan Zhao
2020-03-20 4:09 ` Alex Williamson
2020-03-20 4:20 ` Yan Zhao
2020-03-23 14:45 ` Auger Eric
2020-03-23 11:45 ` Auger Eric
2020-03-24 19:14 ` Kirti Wankhede
2020-03-18 19:41 ` [PATCH v14 Kernel 2/7] vfio iommu: Remove atomicity of ref_count of pinned pages Kirti Wankhede
2020-03-23 11:59 ` Auger Eric
2020-03-18 19:41 ` [PATCH v14 Kernel 3/7] vfio iommu: Add ioctl definition for dirty pages tracking Kirti Wankhede
2020-03-19 3:44 ` Alex Williamson
2020-03-18 19:41 ` [PATCH v14 Kernel 4/7] vfio iommu: Implementation of ioctl " Kirti Wankhede
2020-03-19 3:06 ` Yan Zhao
2020-03-19 4:01 ` Alex Williamson
2020-03-19 4:15 ` Yan Zhao
2020-03-19 4:40 ` Alex Williamson [this message]
2020-03-19 6:15 ` Yan Zhao
2020-03-19 13:06 ` Alex Williamson
2020-03-19 16:57 ` Kirti Wankhede
2020-03-20 0:51 ` Yan Zhao
2020-03-19 3:45 ` Alex Williamson
2020-03-19 14:52 ` Kirti Wankhede
2020-03-19 16:22 ` Alex Williamson
2020-03-19 20:25 ` Kirti Wankhede
2020-03-19 20:54 ` Alex Williamson
2020-03-19 18:57 ` Kirti Wankhede
2020-03-18 19:41 ` [PATCH v14 Kernel 5/7] vfio iommu: Update UNMAP_DMA ioctl to get dirty bitmap before unmap Kirti Wankhede
2020-03-19 3:45 ` Alex Williamson
2020-03-20 8:35 ` Yan Zhao
2020-03-20 15:40 ` Alex Williamson
2020-03-20 15:47 ` Alex Williamson
2020-03-20 19:14 ` Kirti Wankhede
2020-03-20 19:28 ` Alex Williamson
2020-03-23 1:10 ` Yan Zhao
2020-03-18 19:41 ` [PATCH v14 Kernel 6/7] vfio iommu: Adds flag to indicate dirty pages tracking capability support Kirti Wankhede
2020-03-18 19:41 ` [PATCH v14 Kernel 7/7] vfio: Selective dirty page tracking if IOMMU backed device pins pages Kirti Wankhede
2020-03-19 3:45 ` Alex Williamson
2020-03-19 6:24 ` Yan Zhao
2020-03-20 19:41 ` Alex Williamson
2020-03-23 2:43 ` Yan Zhao
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