Re: [PATCH v10 Kernel 4/5] vfio iommu: Implementation of ioctl to for dirty pages tracking.

Yan Zhao
2019-12-17T05:23:33Z

On Tue, Dec 17, 2019 at 04:21:39AM +0800, Kirti Wankhede wrote:
> VFIO_IOMMU_DIRTY_PAGES ioctl performs three operations:
> - Start unpinned pages dirty pages tracking while migration is active and
> device is running, i.e. during pre-copy phase.
> - Stop unpinned pages dirty pages tracking. This is required to stop
> unpinned dirty pages tracking if migration failed or cancelled during
> pre-copy phase. Unpinned pages tracking is clear.
> - Get dirty pages bitmap. Stop unpinned dirty pages tracking and clear
> unpinned pages information on bitmap read. This ioctl returns bitmap of
> dirty pages, its user space application responsibility to copy content
> of dirty pages from source to destination during migration.
>
> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
> Reviewed-by: Neo Jia <cjia@nvidia.com>
> ---
> drivers/vfio/vfio_iommu_type1.c | 210 ++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 203 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 3f6b04f2334f..264449654d3f 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -70,6 +70,7 @@ struct vfio_iommu {
> unsigned int dma_avail;
> bool v2;
> bool nesting;
> + bool dirty_page_tracking;
> };
>
> struct vfio_domain {
> @@ -112,6 +113,7 @@ struct vfio_pfn {
> dma_addr_t iova; /* Device address */
> unsigned long pfn; /* Host pfn */
> atomic_t ref_count;
> + bool unpinned;
> };
>
> struct vfio_regions {
> @@ -244,6 +246,32 @@ static void vfio_remove_from_pfn_list(struct vfio_dma *dma,
> kfree(vpfn);
> }
>
> +static void vfio_remove_unpinned_from_pfn_list(struct vfio_dma *dma, bool warn)
> +{
> + struct rb_node *n = rb_first(&dma->pfn_list);
> +
> + for (; n; n = rb_next(n)) {
> + struct vfio_pfn *vpfn = rb_entry(n, struct vfio_pfn, node);
> +
> + if (warn)
> + WARN_ON_ONCE(vpfn->unpinned);
> +
> + if (vpfn->unpinned)
> + vfio_remove_from_pfn_list(dma, vpfn);
> + }
> +}
> +
> +static void vfio_remove_unpinned_from_dma_list(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_remove_unpinned_from_pfn_list(dma, false);
> + }
> +}
> +
> static struct vfio_pfn *vfio_iova_get_vfio_pfn(struct vfio_dma *dma,
> unsigned long iova)
> {
> @@ -254,13 +282,17 @@ static struct vfio_pfn *vfio_iova_get_vfio_pfn(struct vfio_dma *dma,
> return vpfn;
> }
>
> -static int vfio_iova_put_vfio_pfn(struct vfio_dma *dma, struct vfio_pfn *vpfn)
> +static int vfio_iova_put_vfio_pfn(struct vfio_dma *dma, struct vfio_pfn *vpfn,
> + bool dirty_tracking)
> {
> int ret = 0;
>
> if (atomic_dec_and_test(&vpfn->ref_count)) {
> ret = put_pfn(vpfn->pfn, dma->prot);
if physical page here is put, it may cause problem when pin this iova
next time:
vfio_iommu_type1_pin_pages {
...
vpfn = vfio_iova_get_vfio_pfn(dma, iova);
if (vpfn) {
phys_pfn[i] = vpfn->pfn;
continue;
}
...
}

> - vfio_remove_from_pfn_list(dma, vpfn);
> + if (dirty_tracking)
> + vpfn->unpinned = true;
> + else
> + vfio_remove_from_pfn_list(dma, vpfn);
so the unpinned pages before dirty page tracking is not treated as
dirty?

> }
> return ret;
> }
> @@ -504,7 +536,7 @@ static int vfio_pin_page_external(struct vfio_dma *dma, unsigned long vaddr,
> }
>
> static int vfio_unpin_page_external(struct vfio_dma *dma, dma_addr_t iova,
> - bool do_accounting)
> + bool do_accounting, bool dirty_tracking)
> {
> int unlocked;
> struct vfio_pfn *vpfn = vfio_find_vpfn(dma, iova);
> @@ -512,7 +544,10 @@ static int vfio_unpin_page_external(struct vfio_dma *dma, dma_addr_t iova,
> if (!vpfn)
> return 0;
>
> - unlocked = vfio_iova_put_vfio_pfn(dma, vpfn);
> + if (vpfn->unpinned)
> + return 0;
> +
> + unlocked = vfio_iova_put_vfio_pfn(dma, vpfn, dirty_tracking);
>
> if (do_accounting)
> vfio_lock_acct(dma, -unlocked, true);
> @@ -583,7 +618,8 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
>
> ret = vfio_add_to_pfn_list(dma, iova, phys_pfn[i]);
> if (ret) {
> - vfio_unpin_page_external(dma, iova, do_accounting);
> + vfio_unpin_page_external(dma, iova, do_accounting,
> + false);
> goto pin_unwind;
> }
> }
> @@ -598,7 +634,7 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
>
> iova = user_pfn[j] << PAGE_SHIFT;
> dma = vfio_find_dma(iommu, iova, PAGE_SIZE);
> - vfio_unpin_page_external(dma, iova, do_accounting);
> + vfio_unpin_page_external(dma, iova, do_accounting, false);
> phys_pfn[j] = 0;
> }
> pin_done:
> @@ -632,7 +668,8 @@ static int vfio_iommu_type1_unpin_pages(void *iommu_data,
> dma = vfio_find_dma(iommu, iova, PAGE_SIZE);
> if (!dma)
> goto unpin_exit;
> - vfio_unpin_page_external(dma, iova, do_accounting);
> + vfio_unpin_page_external(dma, iova, do_accounting,
> + iommu->dirty_page_tracking);
> }
>
> unpin_exit:
> @@ -850,6 +887,88 @@ static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu)
> return bitmap;
> }
>
> +/*
> + * start_iova is the reference from where bitmaping started. This is called
> + * from DMA_UNMAP where start_iova can be different than iova
> + */
> +
> +static void vfio_iova_dirty_bitmap(struct vfio_iommu *iommu, dma_addr_t iova,
> + size_t size, uint64_t pgsize,
> + dma_addr_t start_iova, unsigned long *bitmap)
> +{
> + struct vfio_dma *dma;
> + dma_addr_t i = iova;
> + unsigned long pgshift = __ffs(pgsize);
> +
> + while ((dma = vfio_find_dma(iommu, i, pgsize))) {
> + /* mark all pages dirty if all pages are pinned and mapped. */
> + if (dma->iommu_mapped) {
This prevents pass-through devices from calling vfio_pin_pages to do
fine grained log dirty.
> + dma_addr_t iova_limit;
> +
> + iova_limit = (dma->iova + dma->size) < (iova + size) ?
> + (dma->iova + dma->size) : (iova + size);
> +
> + for (; i < iova_limit; i += pgsize) {
> + unsigned int start;
> +
> + start = (i - start_iova) >> pgshift;
> +
> + __bitmap_set(bitmap, start, 1);
> + }
> + if (i >= iova + size)
> + return;
> + } else {
> + struct rb_node *n = rb_first(&dma->pfn_list);
> + bool found = false;
> +
> + for (; n; n = rb_next(n)) {
> + struct vfio_pfn *vpfn = rb_entry(n,
> + struct vfio_pfn, node);
> + if (vpfn->iova >= i) {
> + found = true;
> + break;
> + }
> + }
> +
> + if (!found) {
> + i += dma->size;
> + continue;
> + }
> +
> + for (; n; n = rb_next(n)) {
> + unsigned int start;
> + struct vfio_pfn *vpfn = rb_entry(n,
> + struct vfio_pfn, node);
> +
> + if (vpfn->iova >= iova + size)
> + return;
> +
> + start = (vpfn->iova - start_iova) >> pgshift;
> +
> + __bitmap_set(bitmap, start, 1);
> +
> + i = vpfn->iova + pgsize;
> + }
> + }
> + vfio_remove_unpinned_from_pfn_list(dma, false);
> + }
> +}
> +
> +static long verify_bitmap_size(unsigned long npages, unsigned long bitmap_size)
> +{
> + long bsize;
> +
> + if (!bitmap_size || bitmap_size > SIZE_MAX)
> + return -EINVAL;
> +
> + bsize = ALIGN(npages, BITS_PER_LONG) / sizeof(unsigned long);
> +
> + if (bitmap_size < bsize)
> + return -EINVAL;
> +
> + return bsize;
> +}
> +
> static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
> struct vfio_iommu_type1_dma_unmap *unmap)
> {
> @@ -2298,6 +2417,83 @@ 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 range;
> + uint32_t mask = VFIO_IOMMU_DIRTY_PAGES_FLAG_START |
> + VFIO_IOMMU_DIRTY_PAGES_FLAG_STOP |
> + VFIO_IOMMU_DIRTY_PAGES_FLAG_GET_BITMAP;
> + int ret;
> +
> + if (!iommu->v2)
> + return -EACCES;
> +
> + minsz = offsetofend(struct vfio_iommu_type1_dirty_bitmap,
> + bitmap);
> +
> + if (copy_from_user(&range, (void __user *)arg, minsz))
> + return -EFAULT;
> +
> + if (range.argsz < minsz || range.flags & ~mask)
> + return -EINVAL;
> +
> + if (range.flags & VFIO_IOMMU_DIRTY_PAGES_FLAG_START) {
> + iommu->dirty_page_tracking = true;
> + return 0;
> + } else if (range.flags & VFIO_IOMMU_DIRTY_PAGES_FLAG_STOP) {
> + iommu->dirty_page_tracking = false;
> +
> + mutex_lock(&iommu->lock);
> + vfio_remove_unpinned_from_dma_list(iommu);
> + mutex_unlock(&iommu->lock);
> + return 0;
> +
> + } else if (range.flags &
> + VFIO_IOMMU_DIRTY_PAGES_FLAG_GET_BITMAP) {
> + uint64_t iommu_pgmask;
> + unsigned long pgshift = __ffs(range.pgsize);
> + unsigned long *bitmap;
> + long bsize;
> +
> + iommu_pgmask =
> + ((uint64_t)1 << __ffs(vfio_pgsize_bitmap(iommu))) - 1;
> +
> + if (((range.pgsize - 1) & iommu_pgmask) !=
> + (range.pgsize - 1))
> + return -EINVAL;
> +
> + if (range.iova & iommu_pgmask)
> + return -EINVAL;
> + if (!range.size || range.size > SIZE_MAX)
> + return -EINVAL;
> + if (range.iova + range.size < range.iova)
> + return -EINVAL;
> +
> + bsize = verify_bitmap_size(range.size >> pgshift,
> + range.bitmap_size);
> + if (bsize)
> + return ret;
> +
> + bitmap = kmalloc(bsize, GFP_KERNEL);
> + if (!bitmap)
> + return -ENOMEM;
> +
> + ret = copy_from_user(bitmap,
> + (void __user *)range.bitmap, bsize) ? -EFAULT : 0;
> + if (ret)
> + goto bitmap_exit;
> +
> + iommu->dirty_page_tracking = false;
why iommu->dirty_page_tracking is false here?
suppose this ioctl can be called several times.

Thanks
Yan
> + mutex_lock(&iommu->lock);
> + vfio_iova_dirty_bitmap(iommu, range.iova, range.size,
> + range.pgsize, range.iova, bitmap);
> + mutex_unlock(&iommu->lock);
> +
> + ret = copy_to_user((void __user *)range.bitmap, bitmap,
> + range.bitmap_size) ? -EFAULT : 0;
> +bitmap_exit:
> + kfree(bitmap);
> + return ret;
> + }
> }
>
> return -ENOTTY;
> --
> 2.7.0
>