Re: [RFC PATCH] KVM: optimize apic interrupt delivery

[Avi Kivity <avi@redhat.com>]

On 09/11/2012 12:57 PM, Gleb Natapov wrote:

>> > If you get -ENOMEM when allocating a page without GFP_ATOMIC (or
>> > GFP_NOIO etc) then the entire host is dead anyway.  The same thing can
>> > happen if the guest (or userspace) touches a yet-unallocated page, or if
>> > the page fault path fails to allocate mmu pages, or any of a thousand
>> > other allocations we have all over.
>> Then it is just simpler to sigkill the guest right away. What's the
>> point in returning error if you believe that userspace can't handle it
>> and will likely not run long enough to even get to userspace due to
>> memory shortage.
>> 
> And although this is not the route I will go the question remains. How
> do we return to the kernel after userspace exit in the middle of IO that
> is handled by an in-kernel device. Looks like the kernel will expect
> emulation result from userspace on next ioctl(RUN).

Option 1 is to rewind everything to before the instruction.  Option 2 is
to document that errors are not recoverable.

-- 
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