• David Gibson's avatar
    iommu: Add universal DMA helper functions · d86a77f8
    David Gibson authored
    
    
    Not that long ago, every device implementation using DMA directly
    accessed guest memory using cpu_physical_memory_*().  This meant that
    adding support for a guest visible IOMMU would require changing every
    one of these devices to go through IOMMU translation.
    
    Shortly before qemu 1.0, I made a start on fixing this by providing
    helper functions for PCI DMA.  These are currently just stubs which
    call the direct access functions, but mean that an IOMMU can be
    implemented in one place, rather than for every PCI device.
    
    Clearly, this doesn't help for non PCI devices, which could also be
    IOMMU translated on some platforms.  It is also problematic for the
    devices which have both PCI and non-PCI version (e.g. OHCI, AHCI) - we
    cannot use the the pci_dma_*() functions, because they assume the
    presence of a PCIDevice, but we don't want to have to check between
    pci_dma_*() and cpu_physical_memory_*() every time we do a DMA in the
    device code.
    
    This patch makes the first step on addressing both these problems, by
    introducing new (stub) dma helper functions which can be used for any
    DMA capable device.
    
    These dma functions take a DMAContext *, a new (currently empty)
    variable describing the DMA address space in which the operation is to
    take place.  NULL indicates untranslated DMA directly into guest
    physical address space.  The intention is that in future non-NULL
    values will given information about any necessary IOMMU translation.
    
    DMA using devices must obtain a DMAContext (or, potentially, contexts)
    from their bus or platform.  For now this patch just converts the PCI
    wrappers to be implemented in terms of the universal wrappers,
    converting other drivers can take place over time.
    
    Cc: Michael S. Tsirkin <mst@redhat.com>
    Cc: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
    Cc: Richard Henderson <rth@twiddle.net>
    Signed-off-by: default avatarDavid Gibson <david@gibson.dropbear.id.au>
    Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
    Signed-off-by: default avatarAnthony Liguori <aliguori@us.ibm.com>
    d86a77f8
dma.h 5.56 KB