• Ian Campbell's avatar
    xen: swiotlb: handle sizeof(dma_addr_t) != sizeof(phys_addr_t) · e17b2f11
    Ian Campbell authored
    
    
    The use of phys_to_machine and machine_to_phys in the phys<=>bus conversions
    causes us to lose the top bits of the DMA address if the size of a DMA address is not the same as the size of the phyiscal address.
    
    This can happen in practice on ARM where foreign pages can be above 4GB even
    though the local kernel does not have LPAE page tables enabled (which is
    totally reasonable if the guest does not itself have >4GB of RAM). In this
    case the kernel still maps the foreign pages at a phys addr below 4G (as it
    must) but the resulting DMA address (returned by the grant map operation) is
    much higher.
    
    This is analogous to a hardware device which has its view of RAM mapped up
    high for some reason.
    
    This patch makes I/O to foreign pages (specifically blkif) work on 32-bit ARM
    systems with more than 4GB of RAM.
    Signed-off-by: default avatarIan Campbell <ian.campbell@citrix.com>
    Signed-off-by: default avatarStefano Stabellini <stefano.stabellini@eu.citrix.com>
    e17b2f11