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Message-ID: <20221214173418.iwovyxlbogkspjxy@skbuf> Date: Wed, 14 Dec 2022 19:34:18 +0200 From: Vladimir Oltean <vladimir.oltean@....com> To: Robin Murphy <robin.murphy@....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 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[] = {
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