• Alexey Kardashevskiy's avatar
    powerpc/iommu/powernv: Release replaced TCE · 05c6cfb9
    Alexey Kardashevskiy authored
    At the moment writing new TCE value to the IOMMU table fails with EBUSY
    if there is a valid entry already. However PAPR specification allows
    the guest to write new TCE value without clearing it first.
    
    Another problem this patch is addressing is the use of pool locks for
    external IOMMU users such as VFIO. The pool locks are to protect
    DMA page allocator rather than entries and since the host kernel does
    not control what pages are in use, there is no point in pool locks and
    exchange()+put_page(oldtce) is sufficient to avoid possible races.
    
    This adds an exchange() callback to iommu_table_ops which does the same
    thing as set() plus it returns replaced TCE and DMA direction so
    the caller can release the pages afterwards. The exchange() receives
    a physical address unlike set() which receives linear mapping address;
    and returns a physical address as the clear() does.
    
    This implements exchange() for P5IOC2/IODA/IODA2. This adds a requirement
    for a platform to have exchange() implemented in order to support VFIO.
    
    This replaces iommu_tce_build() and iommu_clear_tce() with
    a single iommu_tce_xchg().
    
    This makes sure that TCE permission bits are not set in TCE passed to
    IOMMU API as those are to be calculated by platform code from
    DMA direction.
    
    This moves SetPageDirty() to the IOMMU code to make it work for both
    VFIO ioctl interface in in-kernel TCE acceleration (when it becomes
    available later).
    Signed-off-by: default avatarAlexey Kardashevskiy <aik@ozlabs.ru>
    [aw: for the vfio related changes]
    Acked-by: default avatarAlex Williamson <alex.williamson@redhat.com>
    Reviewed-by: default avatarDavid Gibson <david@gibson.dropbear.id.au>
    Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
    05c6cfb9
pci.h 6.75 KB