On 01/26/2011 11:05 AM, Sheng Yang wrote:
On Tuesday 25 January 2011 20:47:38 Avi Kivity wrote: > On 01/19/2011 10:21 AM, Sheng Yang wrote: > > > > We already got an guest MMIO address for that in the exit > > > > information. I've created a chain of handler in qemu to handle it. > > > > > > But we already decoded the table and entry... > > > > But the handler is still wrapped by vcpu_mmio_write(), as a part of MMIO. > > So it's not quite handy to get the table and entry out. > > The kernel handler can create a new kvm_run exit description. > > > Also the updater in the userspace > > > > can share the most logic with ordinary userspace MMIO handler, which take > > address as parameter. So I think we don't need to pass the decoded > > table_id and entry to userspace. > > It's mixing layers, which always leads to trouble. For one, the user > handler shouldn't do anything with the write since the kernel already > wrote it into the table. For another, if two vcpus write to the same > entry simultaneously, you could see different ordering in the kernel and > userspace, and get inconsistent results. The shared logic is not about writing, but about interpret what's written. Old MMIO handler would write the data, then interpret it; and our new MMIO would only share the logic of interpretation. I think that's fair enough?
It dosn't make sense for an API point of view. You registered a table of entries, you expect an exit on that table to point to the table and entry that got changed.
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