[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] [PATCH V2] mem_event: Allow emulating an instruction that caused a page fault

Ok, talking only about writes, we have the destination operand, plus all
the pagetables (for setting Accessed bits) plus any stacks and TSSes
needed in delivering faults; something like 32 pages for the full
double-fault scenario.

I see, but then, even setting aside Andres' argument that having all possible events sent to userspace is far from trivial, doing so would completely cripple the monitored domain speed-wise. Imagine having userspace having to decide if it allows a write 32 times per one instruction.

Even with its limitations, this patch at least gives us a shot at looking at what the domain does with memory - the existing model (releasing the page completely to allow the write) is not fit for anything like this at all.

So far, between the requirements of reasonable demands on the domU, and satisfactory levels of control provided by the received mem_events, at least as far as writes go, the patch's done it's job quite nicely.

Razvan Cojocaru

Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.