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 5/7] vfio iommu: Update UNMAP_DMA ioctl to get dirty bitmap before unmap
Date: Fri, 27 Mar 2020 10:12:43 +0530 [thread overview]
Message-ID: <b6524b4a-e6a0-7328-5003-7286f2fd61a8@nvidia.com> (raw)
In-Reply-To: <20200327000426.GA26419@joy-OptiPlex-7040>
On 3/27/2020 5:34 AM, Yan Zhao wrote:
> On Fri, Mar 27, 2020 at 05:39:44AM +0800, Kirti Wankhede wrote:
>>
>>
>> On 3/25/2020 7:48 AM, Yan Zhao wrote:
>>> On Wed, Mar 25, 2020 at 03:32:37AM +0800, Kirti Wankhede wrote:
>>>> DMA mapped pages, including those pinned by mdev vendor drivers, might
>>>> get unpinned and unmapped while migration is active and device is still
>>>> running. For example, in pre-copy phase while guest driver could access
>>>> those pages, host device or vendor driver can dirty these mapped pages.
>>>> Such pages should be marked dirty so as to maintain memory consistency
>>>> for a user making use of dirty page tracking.
>>>>
>>>> To get bitmap during unmap, user should allocate memory for bitmap, set
>>>> size of allocated memory, set page size to be considered for bitmap and
>>>> set flag VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP.
>>>>
>>>> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
>>>> Reviewed-by: Neo Jia <cjia@nvidia.com>
>>>> ---
>>>> drivers/vfio/vfio_iommu_type1.c | 54 ++++++++++++++++++++++++++++++++++++++---
>>>> include/uapi/linux/vfio.h | 10 ++++++++
>>>> 2 files changed, 60 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
>>>> index 27ed069c5053..b98a8d79e13a 100644
>>>> --- a/drivers/vfio/vfio_iommu_type1.c
>>>> +++ b/drivers/vfio/vfio_iommu_type1.c
>>>> @@ -982,7 +982,8 @@ static int verify_bitmap_size(uint64_t npages, uint64_t bitmap_size)
>>>> }
>>>>
>>>> static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
>>>> - struct vfio_iommu_type1_dma_unmap *unmap)
>>>> + struct vfio_iommu_type1_dma_unmap *unmap,
>>>> + struct vfio_bitmap *bitmap)
>>>> {
>>>> uint64_t mask;
>>>> struct vfio_dma *dma, *dma_last = NULL;
>>>> @@ -1033,6 +1034,10 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
>>>> * will be returned if these conditions are not met. The v2 interface
>>>> * will only return success and a size of zero if there were no
>>>> * mappings within the range.
>>>> + *
>>>> + * When VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP flag is set, unmap request
>>>> + * must be for single mapping. Multiple mappings with this flag set is
>>>> + * not supported.
>>>> */
>>>> if (iommu->v2) {
>>>> dma = vfio_find_dma(iommu, unmap->iova, 1);
>>>> @@ -1040,6 +1045,13 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
>>>> ret = -EINVAL;
>>>> goto unlock;
>>>> }
>>>> +
>>>> + if ((unmap->flags & VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) &&
>>>> + (dma->iova != unmap->iova || dma->size != unmap->size)) {
>>> potential NULL pointer!
>>>
>>> And could you address the comments in v14?
>>> How to handle DSI unmaps in vIOMMU
>>> (https://lore.kernel.org/kvm/20200323011041.GB5456@joy-OptiPlex-7040/)
>>>
>>
>> Sorry, I drafted reply to it, but I missed to send, it remained in my drafts
>>
>> >
>> > it happens in vIOMMU Domain level invalidation of IOTLB
>> > (domain-selective invalidation, see vtd_iotlb_domain_invalidate() in
>> qemu).
>> > common in VTD lazy mode, and NOT just happening once at boot time.
>> > rather than invalidate page by page, it batches the page invalidation.
>> > so, when this invalidation takes place, even higher level page tables
>> > have been invalid and therefore it has to invalidate a bigger
>> combined range.
>> > That's why we see IOVAs are mapped in 4k pages, but are unmapped in 2M
>> > pages.
>> >
>> > I think those UNMAPs should also have GET_DIRTY_BIMTAP flag on, right?
>>
>>
>> vtd_iotlb_domain_invalidate()
>> vtd_sync_shadow_page_table()
>> vtd_sync_shadow_page_table_range(vtd_as, &ce, 0, UINT64_MAX)
>> vtd_page_walk()
>> vtd_page_walk_level() - walk over specific level for IOVA range
>> vtd_page_walk_one()
>> memory_region_notify_iommu()
>> ...
>> vfio_iommu_map_notify()
>>
>> In the above trace, isn't page walk will take care of creating proper
>> IOTLB entry which should be same as created during mapping for that
>> IOTLB entry?
>>
> No. It does walk the page table, but as it's dsi (delay & batched unmap),
> pages table entry for a whole 2M (the higher level, not last level for 4K)
> range is invalid, so the iotlb->addr_mask what vfio_iommu_map_notify()
> receives is (2M - 1), not the same as the size for map.
>
When do this happen? during my testing I never hit this case. How can I
hit this case?
In this case, will adjacent whole vfio_dmas will be clubbed together or
will there be any intersection of vfio_dmas?
Thanks,
Kirti
next prev parent reply other threads:[~2020-03-27 4:43 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
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 1/7] vfio: KABI for migration interface for device state Kirti Wankhede
2020-03-26 10:41 ` Cornelia Huck
2020-03-26 21:39 ` Kirti Wankhede
2020-03-24 19:32 ` [PATCH v16 Kernel 2/7] vfio iommu: Remove atomicity of ref_count of pinned pages Kirti Wankhede
2020-03-26 10:49 ` Cornelia Huck
2020-03-26 21:45 ` Kirti Wankhede
2020-03-24 19:32 ` [PATCH v16 Kernel 3/7] vfio iommu: Add ioctl definition for dirty pages tracking Kirti Wankhede
2020-03-24 19:32 ` [PATCH v16 Kernel 4/7] vfio iommu: Implementation of ioctl " Kirti Wankhede
2020-03-24 20:37 ` Alex Williamson
2020-03-24 20:45 ` Alex Williamson
2020-03-24 21:48 ` Kirti Wankhede
2020-03-24 19:32 ` [PATCH v16 Kernel 5/7] vfio iommu: Update UNMAP_DMA ioctl to get dirty bitmap before unmap Kirti Wankhede
2020-03-25 2:18 ` Yan Zhao
2020-03-26 21:39 ` Kirti Wankhede
2020-03-27 0:04 ` Yan Zhao
2020-03-27 4:42 ` Kirti Wankhede [this message]
2020-03-30 2:15 ` Yan Zhao
2020-04-01 18:04 ` Kirti Wankhede
2020-03-24 19:32 ` [PATCH v16 Kernel 6/7] vfio iommu: Adds flag to indicate dirty pages tracking capability support Kirti Wankhede
2020-03-24 19:32 ` [PATCH v16 Kernel 7/7] vfio: Selective dirty page tracking if IOMMU backed device pins pages Kirti Wankhede
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