* Re: [PATCH] dma-mapping: don't clear GFP_ZERO in dma_alloc_attrs
2018-03-28 13:35 ` [PATCH] dma-mapping: don't clear GFP_ZERO in dma_alloc_attrs Christoph Hellwig
@ 2018-03-28 15:12 ` Evgeniy Didin
2018-04-09 10:52 ` dma-mapping: clear harmful GFP_* flags in common code Alexey Brodkin
2018-03-28 15:40 ` [tip:x86/dma] dma-mapping: Don't clear GFP_ZERO in dma_alloc_attrs tip-bot for Christoph Hellwig
1 sibling, 1 reply; 5+ messages in thread
From: Evgeniy Didin @ 2018-03-28 15:12 UTC (permalink / raw)
To: hch@lst.de, x86@kernel.org
Cc: linux-kernel@vger.kernel.org, sebott@linux.vnet.ibm.com,
linux-arch@vger.kernel.org, iommu@lists.linux-foundation.org,
Evgeniy.Didin@synopsys.com, linux-snps-arc@lists.infradead.org
Adding linux-snps and linux-arch mailing lists.
> Revert the clearing of __GFP_ZERO in dma_alloc_attrs and move it to
> dma_direct_alloc for now. While most common architectures always zero dma
> cohereny allocations (and x86 did so since day one) this is not documented
> and at least arc and s390 do not zero without the explicit __GFP_ZERO
> argument.
This patch fixed Ethernet issues on ARC HSDK.
https://www.spinics.net/lists/kernel/msg2762054.html
Tested-by: Evgeniy Didin <Evgeniy.Didin@synopsys.com>
> Fixes: 57bf5a8963f8 ("dma-mapping: clear harmful GFP_* flags in common code")
> Reported-by: Evgeniy Didin <Evgeniy.Didin@synopsys.com>
> Reported-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> include/linux/dma-mapping.h | 8 ++------
> lib/dma-direct.c | 3 +++
> 2 files changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> index eb9eab4ecd6d..12fedcba9a9a 100644
> --- a/include/linux/dma-mapping.h
> +++ b/include/linux/dma-mapping.h
> @@ -518,12 +518,8 @@ static inline void *dma_alloc_attrs(struct device *dev, size_t size,
> if (dma_alloc_from_dev_coherent(dev, size, dma_handle, &cpu_addr))
> return cpu_addr;
>
> - /*
> - * Let the implementation decide on the zone to allocate from, and
> - * decide on the way of zeroing the memory given that the memory
> - * returned should always be zeroed.
> - */
> - flag &= ~(__GFP_DMA | __GFP_DMA32 | __GFP_HIGHMEM | __GFP_ZERO);
> + /* let the implementation decide on the zone to allocate from: */
> + flag &= ~(__GFP_DMA | __GFP_DMA32 | __GFP_HIGHMEM);
>
> if (!arch_dma_alloc_attrs(&dev, &flag))
> return NULL;
> diff --git a/lib/dma-direct.c b/lib/dma-direct.c
> index 1277d293d4da..c0bba30fef0a 100644
> --- a/lib/dma-direct.c
> +++ b/lib/dma-direct.c
> @@ -59,6 +59,9 @@ void *dma_direct_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
> struct page *page = NULL;
> void *ret;
>
> + /* we always manually zero the memory once we are done: */
> + gfp &= ~__GFP_ZERO;
> +
> /* GFP_DMA32 and GFP_DMA are no ops without the corresponding zones: */
> if (dev->coherent_dma_mask <= DMA_BIT_MASK(ARCH_ZONE_DMA_BITS))
> gfp |= GFP_DMA;
^ permalink raw reply [flat|nested] 5+ messages in thread* [tip:x86/dma] dma-mapping: Don't clear GFP_ZERO in dma_alloc_attrs
2018-03-28 13:35 ` [PATCH] dma-mapping: don't clear GFP_ZERO in dma_alloc_attrs Christoph Hellwig
2018-03-28 15:12 ` Evgeniy Didin
@ 2018-03-28 15:40 ` tip-bot for Christoph Hellwig
1 sibling, 0 replies; 5+ messages in thread
From: tip-bot for Christoph Hellwig @ 2018-03-28 15:40 UTC (permalink / raw)
To: linux-tip-commits
Cc: sebott, tglx, hch, mingo, Evgeniy.Didin, linux-kernel, hpa
Commit-ID: e89f5b37015309a8bdf0b21d08007580b92f92a4
Gitweb: https://git.kernel.org/tip/e89f5b37015309a8bdf0b21d08007580b92f92a4
Author: Christoph Hellwig <hch@lst.de>
AuthorDate: Wed, 28 Mar 2018 15:35:35 +0200
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Wed, 28 Mar 2018 17:34:23 +0200
dma-mapping: Don't clear GFP_ZERO in dma_alloc_attrs
Revert the clearing of __GFP_ZERO in dma_alloc_attrs and move it to
dma_direct_alloc for now. While most common architectures always zero dma
cohereny allocations (and x86 did so since day one) this is not documented
and at least arc and s390 do not zero without the explicit __GFP_ZERO
argument.
Fixes: 57bf5a8963f8 ("dma-mapping: clear harmful GFP_* flags in common code")
Reported-by: Evgeniy Didin <Evgeniy.Didin@synopsys.com>
Reported-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Evgeniy Didin <Evgeniy.Didin@synopsys.com>
Cc: iommu@lists.linux-foundation.org
Link: https://lkml.kernel.org/r/20180328133535.17302-2-hch@lst.de
---
include/linux/dma-mapping.h | 8 ++------
lib/dma-direct.c | 3 +++
2 files changed, 5 insertions(+), 6 deletions(-)
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index eb9eab4ecd6d..12fedcba9a9a 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -518,12 +518,8 @@ static inline void *dma_alloc_attrs(struct device *dev, size_t size,
if (dma_alloc_from_dev_coherent(dev, size, dma_handle, &cpu_addr))
return cpu_addr;
- /*
- * Let the implementation decide on the zone to allocate from, and
- * decide on the way of zeroing the memory given that the memory
- * returned should always be zeroed.
- */
- flag &= ~(__GFP_DMA | __GFP_DMA32 | __GFP_HIGHMEM | __GFP_ZERO);
+ /* let the implementation decide on the zone to allocate from: */
+ flag &= ~(__GFP_DMA | __GFP_DMA32 | __GFP_HIGHMEM);
if (!arch_dma_alloc_attrs(&dev, &flag))
return NULL;
diff --git a/lib/dma-direct.c b/lib/dma-direct.c
index 1277d293d4da..c0bba30fef0a 100644
--- a/lib/dma-direct.c
+++ b/lib/dma-direct.c
@@ -59,6 +59,9 @@ void *dma_direct_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
struct page *page = NULL;
void *ret;
+ /* we always manually zero the memory once we are done: */
+ gfp &= ~__GFP_ZERO;
+
/* GFP_DMA32 and GFP_DMA are no ops without the corresponding zones: */
if (dev->coherent_dma_mask <= DMA_BIT_MASK(ARCH_ZONE_DMA_BITS))
gfp |= GFP_DMA;
^ permalink raw reply related [flat|nested] 5+ messages in thread