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Re: [PATCH Kernel v20 4/8] vfio iommu: Add ioctl definition for dirty pa
From: |
Cornelia Huck |
Subject: |
Re: [PATCH Kernel v20 4/8] vfio iommu: Add ioctl definition for dirty pages tracking |
Date: |
Tue, 19 May 2020 18:00:59 +0200 |
On Tue, 19 May 2020 09:53:56 -0600
Alex Williamson <address@hidden> wrote:
> On Tue, 19 May 2020 17:35:07 +0200
> Cornelia Huck <address@hidden> wrote:
>
> > On Fri, 15 May 2020 23:05:24 +0530
> > Kirti Wankhede <address@hidden> wrote:
> >
> > > On 5/15/2020 4:29 PM, Cornelia Huck wrote:
> > > > On Fri, 15 May 2020 02:07:43 +0530
> > > > Kirti Wankhede <address@hidden> wrote:
> > > >
> > > >> IOMMU container maintains a list of all pages pinned by vfio_pin_pages
> > > >> API.
> > > >> All pages pinned by vendor driver through this API should be
> > > >> considered as
> > > >> dirty during migration. When container consists of IOMMU capable
> > > >> device and
> > > >> all pages are pinned and mapped, then all pages are marked dirty.
> > > >> Added support to start/stop dirtied pages tracking and to get bitmap
> > > >> of all
> > > >> dirtied pages for requested IO virtual address range.
> > > >>
> > > >> Signed-off-by: Kirti Wankhede <address@hidden>
> > > >> Reviewed-by: Neo Jia <address@hidden>
> > > >> ---
> > > >> include/uapi/linux/vfio.h | 55
> > > >> +++++++++++++++++++++++++++++++++++++++++++++++
> > > >> 1 file changed, 55 insertions(+)
> >
> > (...)
> >
> > > >> + * When IOCTL is called with VFIO_IOMMU_DIRTY_PAGES_FLAG_GET_BITMAP
> > > >> flag set,
> > > >> + * IOCTL returns dirty pages bitmap for IOMMU container during
> > > >> migration for
> > > >> + * given IOVA range.
> > > >
> > > > "Calling the IOCTL with VFIO_IOMMU_DIRTY_PAGES_GET_BITMAP returns the
> > > > dirty pages bitmap for the IOMMU container for a given IOVA range." ?
> > > >
> > > > Q: How does this interact with the two other operations? I imagine
> > > > getting an empty bitmap before _START
> > >
> > > No, if dirty page tracking is not started, get_bitmap IOCTL will fail
> > > with -EINVAL.
> > >
> > > > and a bitmap-in-progress between
> > > > _START and _STOP. > After _STOP, will subsequent calls always give the
> > > > same bitmap?
> > > >
> > >
> > > No, return -EINVAL.
> >
> > Maybe add
> >
> > "If the IOCTL has not yet been called with
> > VFIO_IOMMU_DIRTY_PAGES_FLAG_START, or if it has been called with
> > VFIO_IOMMU_DIRTY_PAGES_FLAG_STOP, calling it with
> > VFIO_IOMMU_DIRTY_PAGES_FLAG_GET_BITMAP will return -EINVAL." ?
>
> Let's not specify ourselves into a corner, I think we can simply say
> that the dirty bitmap is only available while dirty logging is enabled.
> We certainly don't need to specify specific errno values that'll trip
> us up later.
"If dirty logging is not enabled, an error will be returned." ?
(...)
> > > >> Caller must set argsz including size of structure
> > > >> + * vfio_iommu_type1_dirty_bitmap_get.
> > > >
> > > > s/Caller/The caller/
> > > >
> > > > Does argz also include the size of the bitmap?
> > >
> > > No.
> >
> > "The caller must set argsz to a value including the size of stuct
> > vfio_io_type1_dirty_bitmap_get, but excluding the size of the actual
> > bitmap." ?
>
> Yes, it wouldn't make sense for argsz to include the size of the bitmap
> itself, that's accessed independently via a user provided pointer and
> we have a separate size field for that. Thanks,
>
> Alex
Yes, I just wanted to make it as obvious as possible to make it easier
for folks trying to interact with this interface.
[PATCH Kernel v20 5/8] vfio iommu: Implementation of ioctl for dirty pages tracking, Kirti Wankhede, 2020/05/14
[PATCH Kernel v20 6/8] vfio iommu: Update UNMAP_DMA ioctl to get dirty bitmap before unmap, Kirti Wankhede, 2020/05/14