Re: [PATCH 1/2] kvm: fix spurious interrupt with irqfd

[Jan Kiszka <jan.kiszka@siemens.com>]

Michael S. Tsirkin wrote:
>>>> I just wonder how broad
>>>> the impact of a broken or non-existent eventfd subsystem for kvm-kmod
>>>> is. Any thoughts welcome.
>>> How do you handle kernels that don't export eventfd_ctx_fileget?
>> Now that you mention it: not yet properly. So far we pass the file
>> struct as pseudo eventfd_ctx around on < 2.6.31. But now that I peek
>> into the struct in kvm_eventfd_ctx_remove_wait_queue, this should should
>> crash. Guess I need to look up that module the same way as I acquire
>> __wake_up_locked[_key].
> 
> This won't work that well: eventfd in upstream
> sends us POLLHUP so we can close the structure,
> in old kernels it doesn't so kernel will crash
> when we try to reference the structure later.
> 

OK, so any host kernel < 2.6.31 will never work for us. Mmh, then I
could only close the gap 2.6.31..2.6.33. vhost will show up in 33...
Will that version already be worth any eventfd wrapping?

Jan

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