linux-kernel - Re: [PATCH v2 3/3] iommu: dart: Add DART iommu driver

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Date:   Fri, 09 Apr 2021 18:50:12 +0200
From:   "Sven Peter" <sven@...npeter.dev>
To:     "Will Deacon" <will@...nel.org>
Cc:     "Robin Murphy" <robin.murphy@....com>,
        "Joerg Roedel" <joro@...tes.org>,
        "Rob Herring" <robh+dt@...nel.org>,
        "Arnd Bergmann" <arnd@...nel.org>, devicetree@...r.kernel.org,
        "Hector Martin" <marcan@...can.st>, linux-kernel@...r.kernel.org,
        "Marc Zyngier" <maz@...nel.org>,
        "Mohamed Mediouni" <mohamed.mediouni@...amail.com>,
        "Stan Skowronek" <stan@...ellium.com>,
        linux-arm-kernel@...ts.infradead.org,
        "Mark Kettenis" <mark.kettenis@...all.nl>,
        "Petr Mladek via iommu" <iommu@...ts.linux-foundation.org>
Subject: Re: [PATCH v2 3/3] iommu: dart: Add DART iommu driver



On Wed, Apr 7, 2021, at 12:42, Will Deacon wrote:
> On Sun, Mar 28, 2021 at 09:40:09AM +0200, Sven Peter wrote:
> > Apple's new SoCs use iommus for almost all peripherals. These Device
> > Address Resolution Tables must be setup before these peripherals can
> > act as DMA masters.
> > 
> > Signed-off-by: Sven Peter <sven@...npeter.dev>
> > ---
> >  MAINTAINERS                      |   1 +
> >  drivers/iommu/Kconfig            |  14 +
> >  drivers/iommu/Makefile           |   1 +
> >  drivers/iommu/apple-dart-iommu.c | 858 +++++++++++++++++++++++++++++++
> >  4 files changed, 874 insertions(+)
> >  create mode 100644 drivers/iommu/apple-dart-iommu.c
> 
> [...]
> 
> > +/* must be called with held domain->lock */
> > +static int apple_dart_attach_stream(struct apple_dart_domain *domain,
> > +				    struct apple_dart *dart, u32 sid)
> > +{
> > +	unsigned long flags;
> > +	struct apple_dart_stream *stream;
> > +	struct io_pgtable_cfg *pgtbl_cfg;
> > +	int ret;
> > +
> > +	list_for_each_entry(stream, &domain->streams, stream_head) {
> > +		if (stream->dart == dart && stream->sid == sid) {
> > +			stream->num_devices++;
> > +			return 0;
> > +		}
> > +	}
> > +
> > +	spin_lock_irqsave(&dart->lock, flags);
> > +
> > +	if (WARN_ON(dart->used_sids & BIT(sid))) {
> > +		ret = -EINVAL;
> > +		goto error;
> > +	}
> > +
> > +	stream = kzalloc(sizeof(*stream), GFP_KERNEL);
> > +	if (!stream) {
> > +		ret = -ENOMEM;
> > +		goto error;
> > +	}
> 
> Just in case you missed it, a cocci bot noticed that you're using GFP_KERNEL
> to allocate while holding a spinlock here:
> 
> https://lore.kernel.org/r/alpine.DEB.2.22.394.2104041724340.2958@hadrien
> 

Thanks for the reminder!
I haven't replied yet because that one was found later when the bot picked up
a (slightly earlier) version that Marc was using to bring up pcie I believe.
I'll fix it for the next version.


Sven