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Date: Tue, 7 Jul 2020 17:08:24 -0500
From: Jeremy Linton <jeremy.linton@....com>
To: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
Christoph Hellwig <hch@....de>,
Marek Szyprowski <m.szyprowski@...sung.com>,
Robin Murphy <robin.murphy@....com>,
David Rientjes <rientjes@...gle.com>
Cc: linux-rpi-kernel@...ts.infradead.org,
iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dma-pool: use single atomic pool for both DMA zones
Hi,
I spun this up on my 8G model using the PFTF firmware from:
https://github.com/pftf/RPi4/releases
Which allows me to switch between ACPI/DT on the machine. In DT mode it
works fine now, but with ACPI I continue to have failures unless I
disable CMA via cma=0 on the kernel command line. It think that is because
using DT:
[ 0.000000] Reserved memory: created CMA memory pool at
0x0000000037400000, size 64 MiB
using ACPI:
[ 0.000000] cma: Reserved 64 MiB at 0x00000000f8000000
Which is AFAIK because the default arm64 CMA allocation is just below
the arm64_dma32_phys_limit.
Thanks,
On 7/7/20 7:28 AM, Nicolas Saenz Julienne wrote:
> When allocating atomic DMA memory for a device, the dma-pool core
> queries __dma_direct_optimal_gfp_mask() to check which atomic pool to
> use. It turns out the GFP flag returned is only an optimistic guess.
> The pool selected might sometimes live in a zone higher than the
> device's view of memory.
>
> As there isn't a way to grantee a mapping between a device's DMA
> constraints and correct GFP flags this unifies both DMA atomic pools.
> The resulting pool is allocated in the lower DMA zone available, if any,
> so as for devices to always get accessible memory while having the
> flexibility of using dma_pool_kernel for the non constrained ones.
>
> Fixes: c84dc6e68a1d ("dma-pool: add additional coherent pools to map to gfp mask")
> Reported-by: Jeremy Linton <jeremy.linton@....com>
> Suggested-by: Robin Murphy <robin.murphy@....com>
> Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
> ---
> kernel/dma/pool.c | 47 +++++++++++++++++++----------------------------
> 1 file changed, 19 insertions(+), 28 deletions(-)
>
> diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c
> index 8cfa01243ed2..883f7a583969 100644
> --- a/kernel/dma/pool.c
> +++ b/kernel/dma/pool.c
> @@ -13,10 +13,11 @@
> #include <linux/slab.h>
> #include <linux/workqueue.h>
>
> +#define GFP_ATOMIC_POOL_DMA (IS_ENABLED(CONFIG_ZONE_DMA) ? GFP_DMA : \
> + IS_ENABLED(CONFIG_ZONE_DMA32) ? GFP_DMA32 : 0)
> +
> static struct gen_pool *atomic_pool_dma __ro_after_init;
> static unsigned long pool_size_dma;
> -static struct gen_pool *atomic_pool_dma32 __ro_after_init;
> -static unsigned long pool_size_dma32;
> static struct gen_pool *atomic_pool_kernel __ro_after_init;
> static unsigned long pool_size_kernel;
>
> @@ -42,16 +43,13 @@ static void __init dma_atomic_pool_debugfs_init(void)
> return;
>
> debugfs_create_ulong("pool_size_dma", 0400, root, &pool_size_dma);
> - debugfs_create_ulong("pool_size_dma32", 0400, root, &pool_size_dma32);
> debugfs_create_ulong("pool_size_kernel", 0400, root, &pool_size_kernel);
> }
>
> static void dma_atomic_pool_size_add(gfp_t gfp, size_t size)
> {
> - if (gfp & __GFP_DMA)
> + if (gfp & GFP_ATOMIC_POOL_DMA)
> pool_size_dma += size;
> - else if (gfp & __GFP_DMA32)
> - pool_size_dma32 += size;
> else
> pool_size_kernel += size;
> }
> @@ -132,12 +130,11 @@ static void atomic_pool_resize(struct gen_pool *pool, gfp_t gfp)
>
> static void atomic_pool_work_fn(struct work_struct *work)
> {
> - if (IS_ENABLED(CONFIG_ZONE_DMA))
> - atomic_pool_resize(atomic_pool_dma,
> - GFP_KERNEL | GFP_DMA);
> - if (IS_ENABLED(CONFIG_ZONE_DMA32))
> - atomic_pool_resize(atomic_pool_dma32,
> - GFP_KERNEL | GFP_DMA32);
> + gfp_t dma_gfp = GFP_ATOMIC_POOL_DMA;
> +
> + if (dma_gfp)
> + atomic_pool_resize(atomic_pool_dma, GFP_KERNEL | dma_gfp);
> +
> atomic_pool_resize(atomic_pool_kernel, GFP_KERNEL);
> }
>
> @@ -168,6 +165,7 @@ static __init struct gen_pool *__dma_atomic_pool_init(size_t pool_size,
>
> static int __init dma_atomic_pool_init(void)
> {
> + gfp_t dma_gfp = GFP_ATOMIC_POOL_DMA;
> int ret = 0;
>
> /*
> @@ -185,18 +183,13 @@ static int __init dma_atomic_pool_init(void)
> GFP_KERNEL);
> if (!atomic_pool_kernel)
> ret = -ENOMEM;
> - if (IS_ENABLED(CONFIG_ZONE_DMA)) {
> +
> + if (dma_gfp) {
> atomic_pool_dma = __dma_atomic_pool_init(atomic_pool_size,
> - GFP_KERNEL | GFP_DMA);
> + GFP_KERNEL | dma_gfp);
> if (!atomic_pool_dma)
> ret = -ENOMEM;
> }
> - if (IS_ENABLED(CONFIG_ZONE_DMA32)) {
> - atomic_pool_dma32 = __dma_atomic_pool_init(atomic_pool_size,
> - GFP_KERNEL | GFP_DMA32);
> - if (!atomic_pool_dma32)
> - ret = -ENOMEM;
> - }
>
> dma_atomic_pool_debugfs_init();
> return ret;
> @@ -206,14 +199,12 @@ postcore_initcall(dma_atomic_pool_init);
> static inline struct gen_pool *dev_to_pool(struct device *dev)
> {
> u64 phys_mask;
> - gfp_t gfp;
> -
> - gfp = dma_direct_optimal_gfp_mask(dev, dev->coherent_dma_mask,
> - &phys_mask);
> - if (IS_ENABLED(CONFIG_ZONE_DMA) && gfp == GFP_DMA)
> - return atomic_pool_dma;
> - if (IS_ENABLED(CONFIG_ZONE_DMA32) && gfp == GFP_DMA32)
> - return atomic_pool_dma32;
> +
> + if (atomic_pool_dma &&
> + dma_direct_optimal_gfp_mask(dev, dev->coherent_dma_mask,
> + &phys_mask))
> + return atomic_pool_dma;
> +
> return atomic_pool_kernel;
> }
>
>
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