From: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
To: Christoph Hellwig <hch@lst.de>
Cc: Amit Pundir <amit.pundir@linaro.org>,
lkml <linux-kernel@vger.kernel.org>,
jeremy.linton@arm.com, iommu@lists.linux-foundation.org,
John Stultz <john.stultz@linaro.org>,
linux-rpi-kernel@lists.infradead.org,
David Rientjes <rientjes@google.com>,
Robin Murphy <robin.murphy@arm.com>,
Sumit Semwal <sumit.semwal@linaro.org>
Subject: Re: [PATCH] dma-pool: Do not allocate pool memory from CMA
Date: Tue, 28 Jul 2020 11:30:32 +0200 [thread overview]
Message-ID: <e39e8f87ed5b4e9da2f08a0651801954e61f4b4e.camel@suse.de> (raw)
In-Reply-To: <20200728091335.GA23744@lst.de>
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On Tue, 2020-07-28 at 11:13 +0200, Christoph Hellwig wrote:
> On Mon, Jul 27, 2020 at 07:56:56PM +0200, Nicolas Saenz Julienne wrote:
> > Hi Christoph,
> > thanks for having a look at this!
> >
> > On Fri, 2020-07-24 at 15:41 +0200, Christoph Hellwig wrote:
> > > Yes, the iommu is an interesting case, and the current code is
> > > wrong for that.
> >
> > Care to expand on this? I do get that checking dma_coherent_ok() on memory
> > that'll later on be mapped into an iommu is kind of silly, although I think
> > harmless in Amir's specific case, since devices have wide enough dma-
ranges.
> > Is
> > there more to it?
>
> I think the problem is that it can lead to not finding suitable memory.
>
> > > Can you try the patch below? It contains a modified version of Nicolas'
> > > patch to try CMA again for the expansion and a new (for now hackish) way
> > > to
> > > not apply the addressability check for dma-iommu allocations.
> > >
> > > diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c
> > > index 6bc74a2d51273e..ec5e525d2b9309 100644
> > > --- a/kernel/dma/pool.c
> > > +++ b/kernel/dma/pool.c
> > > @@ -3,7 +3,9 @@
> > > * Copyright (C) 2012 ARM Ltd.
> > > * Copyright (C) 2020 Google LLC
> > > */
> > > +#include <linux/cma.h>
> > > #include <linux/debugfs.h>
> > > +#include <linux/dma-contiguous.h>
> > > #include <linux/dma-direct.h>
> > > #include <linux/dma-noncoherent.h>
> > > #include <linux/init.h>
> > > @@ -55,6 +57,31 @@ static void dma_atomic_pool_size_add(gfp_t gfp, size_t
> > > size)
> > > pool_size_kernel += size;
> > > }
> > >
> > > +static bool cma_in_zone(gfp_t gfp)
> > > +{
> > > + phys_addr_t end;
> > > + unsigned long size;
> > > + struct cma *cma;
> > > +
> > > + cma = dev_get_cma_area(NULL);
> > > + if (!cma)
> > > + return false;
> > > +
> > > + size = cma_get_size(cma);
> > > + if (!size)
> > > + return false;
> > > + end = cma_get_base(cma) - memblock_start_of_DRAM() + size - 1;
> > > +
> > > + /* CMA can't cross zone boundaries, see cma_activate_area() */
> > > + if (IS_ENABLED(CONFIG_ZONE_DMA) && (gfp & GFP_DMA) &&
> > > + end <= DMA_BIT_MASK(zone_dma_bits))
> > > + return true;
> > > + if (IS_ENABLED(CONFIG_ZONE_DMA32) && (gfp & GFP_DMA32) &&
> > > + end <= DMA_BIT_MASK(32))
> > > + return true;
> > > + return true;
> >
> > IIUC this will always return true given a CMA is present. Which reverts to
> > the
> > previous behaviour (previous as in breaking some rpi4 setups), isn't it?
>
> Was that really what broke the PI? I'll try to get the split out series
> today, which might have a few more tweaks, and then we'll need to test it
> both on these rpi4 setups and Amits phone.
There was two issues with RPi:
- Not validating that pool allocated memory was OK for the device
- Locating all atomic pools in CMA, which doesn't work for all RPi4 devices*,
and IMO misses the point of having multiple pools.
* With ACPI RPi4 we have CMA located in ZONE_DMA32, yet have an atomic pool
consumer, PCIe, that only wants memory in the [0 3GB] area, effectively needing
ZONE_DMA memory.
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next prev parent reply other threads:[~2020-07-28 9:30 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-08 16:49 [PATCH] dma-pool: Do not allocate pool memory from CMA Nicolas Saenz Julienne
2020-07-08 16:58 ` Christoph Hellwig
2020-07-08 23:14 ` Jeremy Linton
2020-07-09 21:47 ` David Rientjes via iommu
2020-07-21 7:21 ` Amit Pundir
2020-07-21 8:39 ` Nicolas Saenz Julienne
2020-07-21 8:54 ` Amit Pundir
2020-07-21 11:15 ` Nicolas Saenz Julienne
2020-07-21 11:28 ` Christoph Hellwig
2020-07-21 11:37 ` Nicolas Saenz Julienne
2020-07-21 12:16 ` Amit Pundir
2020-07-21 12:15 ` Amit Pundir
2020-07-21 12:45 ` Nicolas Saenz Julienne
2020-07-21 15:22 ` Amit Pundir
2020-07-21 16:27 ` Nicolas Saenz Julienne
2020-07-23 5:14 ` Amit Pundir
2020-07-24 9:36 ` Nicolas Saenz Julienne
2020-07-24 11:06 ` Amit Pundir
2020-07-24 13:41 ` Christoph Hellwig
2020-07-24 16:19 ` Amit Pundir
2020-07-24 16:27 ` Christoph Hellwig
2020-07-27 17:56 ` Nicolas Saenz Julienne
2020-07-28 9:13 ` Christoph Hellwig
2020-07-28 9:30 ` Nicolas Saenz Julienne [this message]
2020-07-28 10:09 ` Christoph Hellwig
2020-07-31 1:10 ` Nathan Chancellor
2020-07-31 7:19 ` Amit Pundir
2020-07-31 10:09 ` Nicolas Saenz Julienne
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