Re: [PATCH V6 0/7] fixes for virtual address update

[Alex Williamson <alex.williamson@redhat.com>]

On Mon, 19 Dec 2022 13:42:06 -0500
Steven Sistare <steven.sistare@oracle.com> wrote:

> Alex, Jason, any comments before I post the (hopefully final) version?

I like Kevin's comments, nothing additional from me.  Thanks,

Alex

> On 12/16/2022 1:50 PM, Steve Sistare wrote:
> > Fix bugs in the interfaces that allow the underlying memory object of an
> > iova range to be mapped in a new address space.  They allow userland to
> > indefinitely block vfio mediated device kernel threads, and do not
> > propagate the locked_vm count to a new mm.  Also fix a pre-existing bug
> > that allows locked_vm underflow.
> > 
> > The fixes impose restrictions that eliminate waiting conditions, so
> > revert the dead code:
> >   commit 898b9eaeb3fe ("vfio/type1: block on invalid vaddr")
> >   commit 487ace134053 ("vfio/type1: implement notify callback")
> >   commit ec5e32940cc9 ("vfio: iommu driver notify callback")
> > 
> > Changes in V2 (thanks Alex):
> >   * do not allow group attach while vaddrs are invalid
> >   * add patches to delete dead code
> >   * add WARN_ON for never-should-happen conditions
> >   * check for changed mm in unmap.
> >   * check for vfio_lock_acct failure in remap
> > 
> > Changes in V3 (ditto!):
> >   * return errno at WARN_ON sites, and make it unique
> >   * correctly check for dma task mm change
> >   * change dma owner to current when vaddr is updated
> >   * add Fixes to commit messages
> >   * refactored new code in vfio_dma_do_map
> > 
> > Changes in V4:
> >   * misc cosmetic changes
> > 
> > Changes in V5 (thanks Jason and Kevin):
> >   * grab mm and use it for locked_vm accounting
> >   * separate patches for underflow and restoring locked_vm
> >   * account for reserved pages
> >   * improve error messages
> > 
> > Changes in V6:
> >   * drop "count reserved pages" patch
> >   * add "track locked_vm" patch
> >   * grab current->mm not group_leader->mm
> >   * simplify vfio_change_dma_owner
> >   * fix commit messages
> > 
> > Steve Sistare (7):
> >   vfio/type1: exclude mdevs from VFIO_UPDATE_VADDR
> >   vfio/type1: prevent underflow of locked_vm via exec()
> >   vfio/type1: track locked_vm per dma
> >   vfio/type1: restore locked_vm
> >   vfio/type1: revert "block on invalid vaddr"
> >   vfio/type1: revert "implement notify callback"
> >   vfio: revert "iommu driver notify callback"
> > 
> >  drivers/vfio/container.c        |   5 -
> >  drivers/vfio/vfio.h             |   7 --
> >  drivers/vfio/vfio_iommu_type1.c | 226 ++++++++++++++++++----------------------
> >  include/uapi/linux/vfio.h       |  15 +--
> >  4 files changed, 111 insertions(+), 142 deletions(-)
> >   
>