On 05/20/2011 02:23 AM, Avi Kivity wrote: > On 05/19/2011 11:43 PM, Anthony Liguori wrote: >> On 05/19/2011 09:12 AM, Avi Kivity wrote: >>> The memory API separates the attributes of a memory region (its size, how >>> reads or writes are handled, dirty logging, and coalescing) from where it >>> is mapped and whether it is enabled. This allows a device to configure >>> a memory region once, then hand it off to its parent bus to map it according >>> to the bus configuration. >>> >>> Hierarchical registration also allows a device to compose a region out of >>> a number of sub-regions with different properties; for example some may be >>> RAM while others may be MMIO. >>> >>> + struct { >>> + /* If nonzero, specify bounds on access sizes beyond which a machine >>> + * check is thrown. >>> + */ >>> + unsigned min_access_size; >>> + unsigned max_access_size; >>> + /* If true, unaligned accesses are supported. Otherwise unaligned >>> + * accesses throw machine checks. >>> + */ >>> + bool unaligned; >>> + } valid; >> >> Under what circumstances would this be used? >> >> The behavior of devices that receive non-natural accesses varies wildly. >> >> For PCI devices, invalid accesses almost always return ~0. I can't think of a device where an MCE would occur. > > This was requested by Richard, so I'll let him comment. > Several alpha system chips MCE when accessed with incorrect sizes. E.g. only 64-bit accesses are allowed. Is this structure honestly any better than 4 function pointers? I can't see that it is, myself. r~ -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html