Messages in this thread | | | Date | Sat, 17 Jul 2021 21:41:26 -0400 | From | Sasha Levin <> | Subject | Re: [PATCH AUTOSEL 5.12 42/43] virtio: fix up virtio_disable_cb |
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On Sun, Jul 11, 2021 at 12:23:59AM -0400, Michael S. Tsirkin wrote: >On Sat, Jul 10, 2021 at 07:49:14PM -0400, Sasha Levin wrote: >> From: "Michael S. Tsirkin" <mst@redhat.com> >> >> [ Upstream commit 8d622d21d24803408b256d96463eac4574dcf067 ] >> >> virtio_disable_cb is currently a nop for split ring with event index. >> This is because it used to be always called from a callback when we know >> device won't trigger more events until we update the index. However, >> now that we run with interrupts enabled a lot we also poll without a >> callback so that is different: disabling callbacks will help reduce the >> number of spurious interrupts. >> Further, if using event index with a packed ring, and if being called >> from a callback, we actually do disable interrupts which is unnecessary. >> >> Fix both issues by tracking whenever we get a callback. If that is >> the case disabling interrupts with event index can be a nop. >> If not the case disable interrupts. Note: with a split ring >> there's no explicit "no interrupts" value. For now we write >> a fixed value so our chance of triggering an interupt >> is 1/ring size. It's probably better to write something >> related to the last used index there to reduce the chance >> even further. For now I'm keeping it simple. >> >> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> >> Signed-off-by: Sasha Levin <sashal@kernel.org> > >I am not sure we want this in stable yet. It should in theory >fix the reported interrupt storms but the reporter is on vacation.
Sure, I'll drop it for now. Let me know when you want it re-added. Thanks!
-- Thanks, Sasha
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