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Re: [PATCH v17 Kernel 4/7] vfio iommu: Implementation of ioctl for dirty


From: Yan Zhao
Subject: Re: [PATCH v17 Kernel 4/7] vfio iommu: Implementation of ioctl for dirty pages tracking.
Date: Mon, 30 Mar 2020 20:10:28 -0400
User-agent: Mutt/1.9.4 (2018-02-28)

On Tue, Mar 31, 2020 at 05:19:09AM +0800, Alex Williamson wrote:
> On Mon, 30 Mar 2020 22:20:41 +0530
> Kirti Wankhede <address@hidden> 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.
> > 
> > Fixed below error by changing pgsize type from uint64_t to size_t.
> > Reported-by: kbuild test robot <address@hidden>
> > 
> > All errors:
> > drivers/vfio/vfio_iommu_type1.c:197: undefined reference to `__udivdi3'
> > 
> > drivers/vfio/vfio_iommu_type1.c:225: undefined reference to `__udivdi3'
> > 
> > Signed-off-by: Kirti Wankhede <address@hidden>
> > Reviewed-by: Neo Jia <address@hidden>
> > ---
> >  drivers/vfio/vfio_iommu_type1.c | 266 
> > +++++++++++++++++++++++++++++++++++++++-
> >  1 file changed, 260 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/vfio/vfio_iommu_type1.c 
> > b/drivers/vfio/vfio_iommu_type1.c
> > index 70aeab921d0f..5efebc2b60e1 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 +127,21 @@ 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)
> > +
> > +/*
> > + * Input argument of number of bits to bitmap_set() is unsigned integer, 
> > which
> > + * further casts to signed integer for unaligned multi-bit operation,
> > + * __bitmap_set().
> > + * Then maximum bitmap size supported is 2^31 bits divided by 2^3 
> > bits/byte,
> > + * that is 2^28 (256 MB) which maps to 2^31 * 2^12 = 2^43 (8TB) on 4K page
> > + * system.
> > + */
> > +#define DIRTY_BITMAP_PAGES_MAX     (uint64_t)(INT_MAX - 1)
> 
> 
> This was supposed to be (INT_MAX), not (INT_MAX - 1).  Thanks,
> 
> Alex
> 
> 
> > +#define DIRTY_BITMAP_SIZE_MAX       
> > DIRTY_BITMAP_BYTES(DIRTY_BITMAP_PAGES_MAX)
> > +
> >  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 +191,77 @@ 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_dma *dma, size_t pgsize)
> > +{
> > +   uint64_t npages = dma->size / pgsize;
> > +
> > +   if (npages > DIRTY_BITMAP_PAGES_MAX)
> > +           return -EINVAL;
> > +
> > +   dma->bitmap = kvzalloc(DIRTY_BITMAP_BYTES(npages), GFP_KERNEL);
> > +   if (!dma->bitmap)
> > +           return -ENOMEM;
> > +
> > +   return 0;
> > +}
> > +
> > +static void vfio_dma_bitmap_free(struct vfio_dma *dma)
> > +{
> > +   kfree(dma->bitmap);
> > +   dma->bitmap = NULL;
> > +}
> > +
> > +static void vfio_dma_populate_bitmap(struct vfio_dma *dma, size_t pgsize)
> > +{
> > +   struct rb_node *p;
> > +
> > +   if (RB_EMPTY_ROOT(&dma->pfn_list))
> > +           return;
> > +
> > +   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);
> > +   }
> > +}
> > +
> > +static int vfio_dma_bitmap_alloc_all(struct vfio_iommu *iommu, size_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);
> > +           int ret;
> > +
> > +           ret = vfio_dma_bitmap_alloc(dma, pgsize);
> > +           if (ret) {
> > +                   struct rb_node *p = rb_prev(n);
> > +
> > +                   for (; p; p = rb_prev(p)) {
> > +                           struct vfio_dma *dma = rb_entry(n,
> > +                                                   struct vfio_dma, node);
> > +
> > +                           vfio_dma_bitmap_free(dma);
> > +                   }
> > +                   return ret;
> > +           }
> > +           vfio_dma_populate_bitmap(dma, pgsize);
> > +   }
> > +   return 0;
> > +}
> > +
> > +static void vfio_dma_bitmap_free_all(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);
> > +
> > +           vfio_dma_bitmap_free(dma);
> > +   }
> > +}
> > +
> >  /*
> >   * Helper Functions for host iova-pfn list
> >   */
> > @@ -567,6 +654,18 @@ 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 populated with the smallest supported page
> > +                    * size
> > +                    */
> > +                   bitmap_set(dma->bitmap,
> > +                              (vpfn->iova - dma->iova) >> pgshift, 1);
> > +           }
> >     }
> >  
> >     ret = i;
> > @@ -801,6 +900,7 @@ 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);
> > +   vfio_dma_bitmap_free(dma);
> >     kfree(dma);
> >     iommu->dma_avail++;
> >  }
> > @@ -831,6 +931,57 @@ 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, size_t pgsize,
> > +                             u64 __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;
> > +
> > +   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;
> > +
> > +   /*
> > +    * Re-populate bitmap to include all pinned pages which are considered
> > +    * as dirty but exclude pages which are unpinned and pages which are
> > +    * marked dirty by vfio_dma_rw()
> > +    */
> > +   bitmap_clear(dma->bitmap, 0, npages);
> > +   vfio_dma_populate_bitmap(dma, pgsize);
> > +   return 0;
> > +}
> > +
> > +static int verify_bitmap_size(uint64_t npages, uint64_t bitmap_size)
> > +{
> > +   uint64_t bsize;
> > +
> > +   if (!npages || !bitmap_size || (bitmap_size > DIRTY_BITMAP_SIZE_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)
> >  {
> > @@ -1038,16 +1189,16 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
> >     unsigned long vaddr = map->vaddr;
> >     size_t size = map->size;
> >     int ret = 0, prot = 0;
> > -   uint64_t mask;
> > +   size_t pgsize;
> >     struct vfio_dma *dma;
> >  
> >     /* Verify that none of our __u64 fields overflow */
> >     if (map->size != size || map->vaddr != vaddr || map->iova != iova)
> >             return -EINVAL;
> >  
> > -   mask = ((uint64_t)1 << __ffs(vfio_pgsize_bitmap(iommu))) - 1;
> > +   pgsize = (size_t)1 << __ffs(vfio_pgsize_bitmap(iommu));
> >  
> > -   WARN_ON(mask & PAGE_MASK);
> > +   WARN_ON((pgsize - 1) & PAGE_MASK);
> >  
> >     /* READ/WRITE from device perspective */
> >     if (map->flags & VFIO_DMA_MAP_FLAG_WRITE)
> > @@ -1055,7 +1206,7 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
> >     if (map->flags & VFIO_DMA_MAP_FLAG_READ)
> >             prot |= IOMMU_READ;
> >  
> > -   if (!prot || !size || (size | iova | vaddr) & mask)
> > +   if (!prot || !size || (size | iova | vaddr) & (pgsize - 1))
> >             return -EINVAL;
> >  
> >     /* Don't allow IOVA or virtual address wrap */
> > @@ -1130,6 +1281,12 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
> >     else
> >             ret = vfio_pin_map_dma(iommu, dma, size);
> >  
> > +   if (!ret && iommu->dirty_page_tracking) {
> > +           ret = vfio_dma_bitmap_alloc(dma, pgsize);
> > +           if (ret)
> > +                   vfio_remove_dma(iommu, dma);
> > +   }
> > +
> >  out_unlock:
> >     mutex_unlock(&iommu->lock);
> >     return ret;
> > @@ -2278,6 +2435,93 @@ 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) {
> > +                   size_t pgsize = 1 << __ffs(vfio_pgsize_bitmap(iommu));
> > +
should not use smallest iommu page size as pgsize here as well as for
bitmap_set.
qemu uses 4k for dirty page track.
> > +                   mutex_lock(&iommu->lock);
> > +                   if (!iommu->dirty_page_tracking) {
> > +                           ret = vfio_dma_bitmap_alloc_all(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_all(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;
> > +                   size_t iommu_pgsize =
> > +                            (size_t)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 smallest 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,
> > +                                           range.bitmap.data);
> > +                   else
> > +                           ret = -EINVAL;
> > +                   mutex_unlock(&iommu->lock);
> > +
> > +                   return ret;
> > +           }
> >     }
> >  
> >     return -ENOTTY;
> > @@ -2345,10 +2589,20 @@ 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 populated with the smallest supported page
> > +                    * size
> > +                    */
> > +                   bitmap_set(dma->bitmap, offset >> pgshift,
> > +                              *copied >> pgshift);
> > +           }
> > +   } else
> >             *copied = __copy_from_user(data, (void __user *)vaddr,
> >                                        count) ? 0 : count;
> >     if (kthread)
> 



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