On Mon, Mar 30, 2020 at 09:49:21PM +0800, Kirti Wankhede wrote: > > > On 3/30/2020 8:54 AM, Yan Zhao wrote: > > On Fri, Mar 27, 2020 at 01:28:13PM +0800, Kirti Wankhede wrote: > >> Hit send button little early. > >> > >> > > >> > I checked v12, it's not like what I said. > >> > In v12, bitmaps are generated per vfio_dma, and combination of the > >> > bitmaps are required in order to generate a big bitmap suiting for dirty > >> > query. It can cause problem when offset not aligning. > >> > But what I propose here is to generate an rb tree orthogonal to the tree > >> > of vfio_dma. > >> > > >> > as to CPU cycles saving, I don't think iterating/translating page by page > >> > would achieve that purpose. > >> > > >> > >> Instead of creating one extra rb tree for dirty pages tracking in v10 > >> tried to use dma->pfn_list itself, we tried changes in v10, v11 and v12, > >> latest version is evolved version with best possible approach after > >> discussion. Probably, go through v11 as well. > >> https://patchwork.kernel.org/patch/11298335/ > >> > > I'm not sure why all those previous implementations are bound to > > vfio_dma. for vIOMMU on, in most cases, a vfio_dma is only for a page, > > so generating a one-byte bitmap for a single page in each vfio_dma ? > > is it possible to creating one extra rb tree to keep dirty ranges, and > > one fixed length kernel bitmap whose content is generated on query, > > serving as a bouncing buffer for copy_to_user > > > > One fixed length? what should be fixed value? then isn't it better to > fix the size to dma->size? > > This is also to prevent DoS attack, user space application can query a > very large range. > > >> > >> On 3/27/2020 6:00 AM, Yan Zhao wrote: > >>> On Fri, Mar 27, 2020 at 05:39:01AM +0800, Kirti Wankhede wrote: > >>>> > >>>> > >>>> On 3/25/2020 7:41 AM, Yan Zhao wrote: > >>>>> On Wed, Mar 25, 2020 at 05:18:52AM +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@xxxxxxxxxx> > >>>>>> Reviewed-by: Neo Jia <cjia@xxxxxxxxxx> > >>>>>> --- > >>>>>> 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..874a1a7ae925 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) > >>>>>> +#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, uint64_t pgsize) > >>>>>> +{ > >>>>>> + uint64_t npages = dma->size / pgsize; > >>>>>> + > > If pgsize > dma->size, npages = 0. > > wouldn't it cause problem? > > > > This patch-set supports bitmap for smallest supported page size, i.e. > PAGE_SIZE. vfio_dma_do_map() validates dma->size accordingly. So this > case will not happen. > as far as I know, qemu/kvm uses 4k as the unit for dirty page tracking. so why smallest iommu page size is used here? wouldn't it cause problem? Thanks Yan
