On Mon, 19 Nov 2018 18:25:25 +0100 Michael Mueller <mimu@xxxxxxxxxxxxx> wrote: > Do not call __deliver_io() for adapter interruptions already > pending in the IPM. That is a double effort. They will > be processed as soon the vcpu control is given to SIE. > > Signed-off-by: Michael Mueller <mimu@xxxxxxxxxxxxx> > --- > arch/s390/kvm/interrupt.c | 54 ++++++++++++++++++++++------------------------- > 1 file changed, 25 insertions(+), 29 deletions(-) I think this patch does what it says on the tin, but I'm a bit lost as to the why. (Might make more sense with the gib.) Currently, we are trying to process any I/O interrupts, even if we'd get them delivered via the gisa, when we're out of the SIE anyway. IIRC, while this looks a bit like a belt-and-suspenders approach, it also prevented performance problems when the vcpu did not go back into the SIE immediately (it even may exit to userspace). Also, if you're ignoring the I/O interrupts pending in the ipm, you may end up delivering interrupts with a lower priority (higher isc) first. I'm not sure that's what we want. But maybe I'm just missing another bit of the code that makes this safe. Can you elaborate a bit?
