[PATCH 4/4] powerpc/eeh: Avoid event on passed PE

[Alexander Graf]

> Am 03.06.2014 um 07:54 schrieb Paul Mackerras <paulus at samba.org>:
> 
>> On Tue, May 20, 2014 at 01:25:11PM +0200, Alexander Graf wrote:
>> 
>>> On 20.05.14 10:30, Gavin Shan wrote:
>>> If we detects frozen state on PE that has been passed to guest, we
>>> needn't handle it. Instead, we rely on the guest to detect and recover
>>> it. The patch avoid EEH event on the frozen passed PE so that the guest
>>> can have chance to handle that.
>>> 
>>> Signed-off-by: Gavin Shan <gwshan at linux.vnet.ibm.com>
>> 
>> How does the guest learn about this failure? We'd need to inject an error
>> into it, no?
>> 
>> I think what you want is an irqfd that the in-kernel eeh code notifies when
>> it sees a failure. When such an fd exists, the kernel skips its own error
>> handling.
> 
> Well... we don't have irqfd support for book3s HV upstream yet.  The
> way the current code is, we have to turn on GSI routing, which puts a
> hard and relatively small limit on the hardware IRQ numbers we can use
> as it uses a flat array indexed by hardware IRQ number.  Which is a
> problem that I need to solve somehow,

Please sync up with the ARM folks on this - they were also unhappy about the routing requirements for irqfd ;).

> but it makes using an irqfd
> unattractive in the short term.

For EEH it could as well be a dumb eventfd - really just a side channel that can tell user space that something happened asynchronously :).


Alex