From: Kirti Wankhede <kwankhede@nvidia.com>
To: Yan Zhao <yan.y.zhao@intel.com>
Cc: "alex.williamson@redhat.com" <alex.williamson@redhat.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 v16 Kernel 4/7] vfio iommu: Implementation of ioctl for dirty pages tracking.
Date: Mon, 30 Mar 2020 19:19:21 +0530 [thread overview]
Message-ID: <e91dbf70-05bf-977f-208b-0fb5988af3a8@nvidia.com> (raw)
In-Reply-To: <20200330032437.GD30683@joy-OptiPlex-7040>
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@nvidia.com>
>>>>>> Reviewed-by: Neo Jia <cjia@nvidia.com>
>>>>>> ---
>>>>>> 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.
Thanks,
Kirti
next prev parent reply other threads:[~2020-03-30 13:49 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-24 21:18 [PATCH v16 Kernel 4/7] vfio iommu: Implementation of ioctl for dirty pages tracking Kirti Wankhede
2020-03-25 2:11 ` Yan Zhao
2020-03-26 21:39 ` Kirti Wankhede
2020-03-27 0:30 ` Yan Zhao
2020-03-27 5:07 ` Kirti Wankhede
2020-03-30 2:07 ` Yan Zhao
2020-03-30 20:47 ` Alex Williamson
2020-03-30 23:49 ` Yan Zhao
2020-03-27 5:28 ` Kirti Wankhede
2020-03-30 3:24 ` Yan Zhao
2020-03-30 13:49 ` Kirti Wankhede [this message]
2020-03-30 23:51 ` Yan Zhao
2020-03-31 0:53 ` Alex Williamson
2020-03-31 0:50 ` Yan Zhao
2020-03-31 1:12 ` Alex Williamson
2020-03-31 1:16 ` Yan Zhao
2020-03-31 2:38 ` Alex Williamson
2020-03-31 2:40 ` Zhao, Yan Y
2020-03-27 11:57 ` Dr. David Alan Gilbert
2020-03-27 13:57 ` Alex Williamson
2020-03-27 14:09 ` Dr. David Alan Gilbert
-- strict thread matches above, loose matches on Subject: below --
2020-03-24 19:32 [PATCH v16 Kernel 0/7] KABIs to support migration for VFIO devices Kirti Wankhede
2020-03-24 19:32 ` [PATCH v16 Kernel 4/7] vfio iommu: Implementation of ioctl for dirty pages tracking Kirti Wankhede
2020-03-24 20:37 ` Alex Williamson
2020-03-24 20:45 ` Alex Williamson
2020-03-24 21:48 ` Kirti Wankhede
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