• Konrad Rzeszutek Wilk's avatar
    swiotlb-xen: SWIOTLB library for Xen PV guest with PCI passthrough. · b097186f
    Konrad Rzeszutek Wilk authored
    
    
    This patchset:
    
    PV guests under Xen are running in an non-contiguous memory architecture.
    
    When PCI pass-through is utilized, this necessitates an IOMMU for
    translating bus (DMA) to virtual and vice-versa and also providing a
    mechanism to have contiguous pages for device drivers operations (say DMA
    operations).
    
    Specifically, under Xen the Linux idea of pages is an illusion. It
    assumes that pages start at zero and go up to the available memory. To
    help with that, the Linux Xen MMU provides a lookup mechanism to
    translate the page frame numbers (PFN) to machine frame numbers (MFN)
    and vice-versa. The MFN are the "real" frame numbers. Furthermore
    memory is not contiguous. Xen hypervisor stitches memory for guests
    from different pools, which means there is no guarantee that PFN==MFN
    and PFN+1==MFN+1. Lastly with Xen 4.0, pages (in debug mode) are
    allocated in descending order (high to low), meaning the guest might
    never get any MFN's under the 4GB mark.
    Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    Acked-by: default avatarJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
    Cc: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
    Cc: Albert Herranz <albert_herranz@yahoo.es>
    Cc: Ian Campbell <Ian.Campbell@citrix.com>
    b097186f