Messages in this thread | | | Date | Thu, 21 Dec 2023 11:01:56 +0000 | Subject | Re: [PATCH 2/2] iommu/vt-d: don's issue devTLB flush request when device is disconnected | From | Robin Murphy <> |
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On 2023-12-21 10:42 am, Lukas Wunner wrote: > On Wed, Dec 13, 2023 at 11:54:05AM +0000, Robin Murphy wrote: >> I think if we want to ensure ATCs are invalidated on hot-unplug we need an >> additional pre-removal notifier to take care of that, and that step would >> then want to distinguish between an orderly removal where cleaning up is >> somewhat meaningful, and a surprise removal where it definitely isn't. > > Even if a user starts the process for orderly removal, the device may be > surprise-removed *during* that process. So we cannot assume that the > device is actually accessible if orderly removal has been initiated. > If the form factor supports surprise removal, the device may be gone > at any time.
Sure, whatever we do there's always going to be some unavoidable time-of-check-to-time-of-use race window so we can never guarantee that sending a request to the device will succeed. I was just making the point that if we *have* already detected a surprise removal, then cleaning up its leftover driver model state should still generate a BUS_NOTIFY_REMOVE_DEVICE call, but in that case we can know there's no point trying to send any requests to the device that's already gone.
Thanks, Robin.
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