2018-03-28 13:37:02

by Christoph Hellwig

Subject: tip/x86/dma fix for arc and s390 (at least)

Hi all,

this restores previous __GFP_ZERO passthrough behavior for now as arc and
s390 rely on it. Needs more work to sort out the API mess in the long run.

2018-03-28 13:37:20

by Christoph Hellwig

Subject: [PATCH] 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 <[email protected]>
Reported-by: Sebastian Ott <[email protected]>
Signed-off-by: Christoph Hellwig <[email protected]>
---
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;
--
2.14.2

2018-03-28 15:14:31

by Evgeniy Didin

Subject: Re: [PATCH] dma-mapping: don't clear GFP_ZERO in dma_alloc_attrs

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 <[email protected]>
> Fixes: 57bf5a8963f8 ("dma-mapping: clear harmful GFP_* flags in common code")
> Reported-by: Evgeniy Didin <[email protected]>
> Reported-by: Sebastian Ott <[email protected]>
> Signed-off-by: Christoph Hellwig <[email protected]>
> ---
>  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;

2018-03-28 15:41:46

by tip-bot for Vasyl Gomonovych

Subject: [tip:x86/dma] dma-mapping: Don't clear GFP_ZERO in dma_alloc_attrs

Commit-ID: e89f5b37015309a8bdf0b21d08007580b92f92a4
Gitweb: https://git.kernel.org/tip/e89f5b37015309a8bdf0b21d08007580b92f92a4
Author: Christoph Hellwig <[email protected]>
AuthorDate: Wed, 28 Mar 2018 15:35:35 +0200
Committer: Thomas Gleixner <[email protected]>
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 <[email protected]>
Reported-by: Sebastian Ott <[email protected]>
Signed-off-by: Christoph Hellwig <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Tested-by: Evgeniy Didin <[email protected]>
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]

---
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;

2018-04-09 10:56:45

by Alexey Brodkin

Subject: dma-mapping: clear harmful GFP_* flags in common code

Hello,

May we have
e89f5b370153 ("dma-mapping: Don't clear GFP_ZERO in dma_alloc_attrs")
back-ported to 4.16 kernel as it fixes:

57bf5a8 ("dma-mapping: clear harmful GFP_* flags in common code").

For more info about introduced problem see this thread:
http://lists.infradead.org/pipermail/linux-snps-arc/2018-March/003652.html

-Alexey