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

[Steven Sistare <steven.sistare@oracle.com>]

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

- Steve

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(-)
>