[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] Question about MMIO Region Alignment for PCI Pass-through
Hi there, I have a question about the mmio region access of PCI pass-trough devices. When assigning a PCI device to a guest, pages that contain the device mmio regions are mapped to the guest. Then the guest can directly issue mmio instructions. However, there is a problem that, if a single page has mmio regions of multiple devices, we cannot expose it to the guest. So we need to align PCI memory regions to page size (4K) in dom0 kernel and make sure that each page has only one device's mmio region. I found that this problem was discussed a bit in the following thread. http://lists.xensource.com/archives/html/xen-devel/2007-10/msg01012.html (linux-2.6.18-xen.hg: changest 296) Dom0 parameter "pci-mem-align" seems to help aligning mmio regions. But, at a quick look, mmio regions appear to be aligned not to PAGE_SIZE but to PAGE_SIZE-1. I also have a concern that re-mapping all the PCI resources might do harm to some devices unrelated to PCI pass-through. Does anyone have an idea about this mmio re-mapping issue ? (or is anyone already working on this ?) Regards, ------------------- Yosuke Iwamatsu NEC Corporation _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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