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Date: Wed, 14 Dec 2022 21:25:45 +0000 From: Robin Murphy <robin.murphy@....com> To: Vladimir Oltean <vladimir.oltean@....com> Cc: iommu@...ts.linux.dev, Will Deacon <will@...nel.org>, Joerg Roedel <joro@...tes.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, Michael Walle <michael@...le.cc>, Laurentiu Tudor <laurentiu.tudor@....com>, Claudiu Manoil <claudiu.manoil@....com>, netdev@...r.kernel.org Subject: Re: [PATCH] iommu/arm-smmu: don't unregister on shutdown On 2022-12-14 17:34, Vladimir Oltean wrote: > On Fri, Dec 09, 2022 at 11:24:32AM +0000, Robin Murphy wrote: >>> Fixes: b06c076ea962 ("Revert "iommu/arm-smmu: Make arm-smmu explicitly non-modular"") >> >> I think that's semantically correct, but I'm pretty sure at that point it >> would have been benign in practice - the observable splat will be a much >> more recent fallout from me changing the iommu_device_unregister() behaviour >> in 57365a04c921 ("iommu: Move bus setup to IOMMU device registration"). The >> assumption therein is that unregister would only happen on probe failure, >> before the IOMMU instance is in use, or on module unload, which would not be >> allowed while active devices still hold module references. I overlooked that >> the SMMU drivers were doing what they do, sorry about that. > > Ok, I'll change the Fixes: tag, I didn't notice that iommu_device_unregister() > changed in behavior only later, I just looked at current trees and tried > to infer what went wrong. > >> The change itself looks sensible. The point of this shutdown hook is simply >> not to leave active translations in place that might confuse future software >> after reboot/kexec; any housekeeping in the current kernel state is a waste >> of time anyway. Fancy doing the same for SMMUv3 as well? > > I can try, but I won't have hardware to test. > > Basically the only thing truly relevant for shutdown from arm_smmu_device_remove() > is arm_smmu_device_disable(), would you agree to a patch which changes > things as below? > > diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > index 6d5df91c5c46..d4d8bfee9feb 100644 > --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > @@ -3854,7 +3854,9 @@ static int arm_smmu_device_remove(struct platform_device *pdev) > > static void arm_smmu_device_shutdown(struct platform_device *pdev) > { > - arm_smmu_device_remove(pdev); > + struct arm_smmu_device *smmu = platform_get_drvdata(pdev); > + > + arm_smmu_device_disable(smmu); > } > > static const struct of_device_id arm_smmu_of_match[] = { Looks fine to me! I'll let Will decide if he'd still prefer to do the full remove-calls-shutdown reversal here as well for complete consistency, but I reckon the minimal diff is no bad thing :) Cheers, Robin.
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