[PATCHv3 0/3] dma ops and virtio

[PATCHv3 0/3] dma ops and virtio

[Christian Borntraeger]

Andy,
this is the next and hopefully last version. Seems to work fine
when replacing the previous patches in your tree. I have some
reviews/acks for patch 2 and 3. patch 1 still needs one ack.
Can you replace the patches in your tree and carry them along
with your changes?

old introduction:
-----
There are some attempts to unify the dma ops (Christoph) as well
as some attempts to make virtio use the dma API (Andy).

At kernel summit we concluded that we want to use the same code on all
platforms, whereever possible, so having a dummy dma_op might be the
easiest solution to keep virtio-ccw as similar as possible to
virtio-pci.Together with a fixed up patch set from Andy Lutomirski
this seems to work.  

We will also need a fixup for powerc and QEMU changes to make virtio
work with iommu on power and x86.
----

v2->v3:
- make dma-noop depend on HAS_DMA
- do not do memset on alloc
- prefix patches with *dma*
v1->v2:
- initial testing
- always use dma_noop_ops if device has no private dma_ops
- get rid of setup in virtio_ccw,kvm_virtio
- set CONFIG_HAS_DMA(ATTRS) for virtio (fixes compile for !PCI)
- rename s390_dma_ops to s390_pci_dma_ops


Christian Borntraeger (3):
  dma: Provide simple noop dma ops
  alpha/dma: use common noop dma ops
  s390/dma: Allow per device dma ops

 arch/alpha/kernel/pci-noop.c        | 46 ++---------------------
 arch/s390/Kconfig                   |  3 +-
 arch/s390/include/asm/device.h      |  6 ++-
 arch/s390/include/asm/dma-mapping.h |  6 ++-
 arch/s390/pci/pci.c                 |  1 +
 arch/s390/pci/pci_dma.c             |  4 +-
 include/linux/dma-mapping.h         |  2 +
 lib/Makefile                        |  1 +
 lib/dma-noop.c                      | 75 +++++++++++++++++++++++++++++++++++++
 9 files changed, 96 insertions(+), 48 deletions(-)
 create mode 100644 lib/dma-noop.c

-- 
2.4.3

[PATCH 1/3] dma: Provide simple noop dma ops

[Christian Borntraeger]

We are going to require dma_ops for several common drivers, even for
systems that do have an identity mapping. Lets provide some minimal
no-op dma_ops that can be used for that purpose.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
---
 include/linux/dma-mapping.h |  2 ++
 lib/Makefile                |  1 +
 lib/dma-noop.c              | 75 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 78 insertions(+)
 create mode 100644 lib/dma-noop.c

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index ac07ff0..7912f54 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -66,6 +66,8 @@ struct dma_map_ops {
 	int is_phys;
 };
 
+extern struct dma_map_ops dma_noop_ops;
+
 #define DMA_BIT_MASK(n)	(((n) == 64) ? ~0ULL : ((1ULL<<(n))-1))
 
 #define DMA_MASK_NONE	0x0ULL
diff --git a/lib/Makefile b/lib/Makefile
index 13a7c6a..92d6135 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -18,6 +18,7 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
 obj-$(CONFIG_ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS) += usercopy.o
 lib-$(CONFIG_MMU) += ioremap.o
 lib-$(CONFIG_SMP) += cpumask.o
+lib-$(CONFIG_HAS_DMA) += dma-noop.o
 
 lib-y	+= kobject.o klist.o
 obj-y	+= lockref.o
diff --git a/lib/dma-noop.c b/lib/dma-noop.c
new file mode 100644
index 0000000..7214564
--- /dev/null
+++ b/lib/dma-noop.c
@@ -0,0 +1,75 @@
+/*
+ *	lib/dma-noop.c
+ *
+ * Simple DMA noop-ops that map 1:1 with memory
+ */
+#include <linux/export.h>
+#include <linux/mm.h>
+#include <linux/dma-mapping.h>
+#include <linux/scatterlist.h>
+
+static void *dma_noop_alloc(struct device *dev, size_t size,
+			    dma_addr_t *dma_handle, gfp_t gfp,
+			    struct dma_attrs *attrs)
+{
+	void *ret;
+
+	ret = (void *)__get_free_pages(gfp, get_order(size));
+	if (ret)
+		*dma_handle = virt_to_phys(ret);
+	return ret;
+}
+
+static void dma_noop_free(struct device *dev, size_t size,
+			  void *cpu_addr, dma_addr_t dma_addr,
+			  struct dma_attrs *attrs)
+{
+	free_pages((unsigned long)cpu_addr, get_order(size));
+}
+
+static dma_addr_t dma_noop_map_page(struct device *dev, struct page *page,
+				      unsigned long offset, size_t size,
+				      enum dma_data_direction dir,
+				      struct dma_attrs *attrs)
+{
+	return page_to_phys(page) + offset;
+}
+
+static int dma_noop_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
+			     enum dma_data_direction dir, struct dma_attrs *attrs)
+{
+	int i;
+	struct scatterlist *sg;
+
+	for_each_sg(sgl, sg, nents, i) {
+		void *va;
+
+		BUG_ON(!sg_page(sg));
+		va = sg_virt(sg);
+		sg_dma_address(sg) = (dma_addr_t)virt_to_phys(va);
+		sg_dma_len(sg) = sg->length;
+	}
+
+	return nents;
+}
+
+static int dma_noop_mapping_error(struct device *dev, dma_addr_t dma_addr)
+{
+	return 0;
+}
+
+static int dma_noop_supported(struct device *dev, u64 mask)
+{
+	return 1;
+}
+
+struct dma_map_ops dma_noop_ops = {
+	.alloc			= dma_noop_alloc,
+	.free			= dma_noop_free,
+	.map_page		= dma_noop_map_page,
+	.map_sg			= dma_noop_map_sg,
+	.mapping_error		= dma_noop_mapping_error,
+	.dma_supported		= dma_noop_supported,
+};
+
+EXPORT_SYMBOL(dma_noop_ops);
-- 
2.4.3

Re: [PATCH 1/3] dma: Provide simple noop dma ops

[Joerg Roedel]

On Tue, Nov 03, 2015 at 12:54:37PM +0100, Christian Borntraeger wrote:
> We are going to require dma_ops for several common drivers, even for
> systems that do have an identity mapping. Lets provide some minimal
> no-op dma_ops that can be used for that purpose.
> 
> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> ---
>  include/linux/dma-mapping.h |  2 ++
>  lib/Makefile                |  1 +
>  lib/dma-noop.c              | 75 +++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 78 insertions(+)
>  create mode 100644 lib/dma-noop.c

Reviewed-by: Joerg Roedel <jroedel@suse.de>

[PATCH 2/3] alpha/dma: use common noop dma ops

[Christian Borntraeger]

Some of the alpha pci noop dma ops are identical to the common ones.
Use them.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Joerg Roedel <jroedel@suse.de>
---
 arch/alpha/kernel/pci-noop.c | 46 ++++----------------------------------------
 1 file changed, 4 insertions(+), 42 deletions(-)

diff --git a/arch/alpha/kernel/pci-noop.c b/arch/alpha/kernel/pci-noop.c
index 2b1f4a1..8e735b5e 100644
--- a/arch/alpha/kernel/pci-noop.c
+++ b/arch/alpha/kernel/pci-noop.c
@@ -123,44 +123,6 @@ static void *alpha_noop_alloc_coherent(struct device *dev, size_t size,
 	return ret;
 }
 
-static void alpha_noop_free_coherent(struct device *dev, size_t size,
-				     void *cpu_addr, dma_addr_t dma_addr,
-				     struct dma_attrs *attrs)
-{
-	free_pages((unsigned long)cpu_addr, get_order(size));
-}
-
-static dma_addr_t alpha_noop_map_page(struct device *dev, struct page *page,
-				      unsigned long offset, size_t size,
-				      enum dma_data_direction dir,
-				      struct dma_attrs *attrs)
-{
-	return page_to_pa(page) + offset;
-}
-
-static int alpha_noop_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
-			     enum dma_data_direction dir, struct dma_attrs *attrs)
-{
-	int i;
-	struct scatterlist *sg;
-
-	for_each_sg(sgl, sg, nents, i) {
-		void *va;
-
-		BUG_ON(!sg_page(sg));
-		va = sg_virt(sg);
-		sg_dma_address(sg) = (dma_addr_t)virt_to_phys(va);
-		sg_dma_len(sg) = sg->length;
-	}
-
-	return nents;
-}
-
-static int alpha_noop_mapping_error(struct device *dev, dma_addr_t dma_addr)
-{
-	return 0;
-}
-
 static int alpha_noop_supported(struct device *dev, u64 mask)
 {
 	return mask < 0x00ffffffUL ? 0 : 1;
@@ -168,10 +130,10 @@ static int alpha_noop_supported(struct device *dev, u64 mask)
 
 struct dma_map_ops alpha_noop_ops = {
 	.alloc			= alpha_noop_alloc_coherent,
-	.free			= alpha_noop_free_coherent,
-	.map_page		= alpha_noop_map_page,
-	.map_sg			= alpha_noop_map_sg,
-	.mapping_error		= alpha_noop_mapping_error,
+	.free			= dma_noop_free_coherent,
+	.map_page		= dma_noop_map_page,
+	.map_sg			= dma_noop_map_sg,
+	.mapping_error		= dma_noop_mapping_error,
 	.dma_supported		= alpha_noop_supported,
 };
 
-- 
2.4.3

[PATCH 3/3] s390/dma: Allow per device dma ops

[Christian Borntraeger]

As virtio-ccw now has dma ops, we can no longer default to the PCI ones.
Make use of dev_archdata to keep the dma_ops per device. The pci devices
now use that to override the default, and the default is changed to use
the noop ops for everything that is not PCI. To compile without PCI
support we also have to enable the DMA api with virtio.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Joerg Roedel <jroedel@suse.de>
Acked-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
---
 arch/s390/Kconfig                   | 3 ++-
 arch/s390/include/asm/device.h      | 6 +++++-
 arch/s390/include/asm/dma-mapping.h | 6 ++++--
 arch/s390/pci/pci.c                 | 1 +
 arch/s390/pci/pci_dma.c             | 4 ++--
 5 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 1d57000..04f0e02 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -113,6 +113,7 @@ config S390
 	select GENERIC_FIND_FIRST_BIT
 	select GENERIC_SMP_IDLE_THREAD
 	select GENERIC_TIME_VSYSCALL
+	select HAS_DMA
 	select HAVE_ALIGNED_STRUCT_PAGE if SLUB
 	select HAVE_ARCH_AUDITSYSCALL
 	select HAVE_ARCH_EARLY_PFN_TO_NID
@@ -124,6 +125,7 @@ config S390
 	select HAVE_CMPXCHG_DOUBLE
 	select HAVE_CMPXCHG_LOCAL
 	select HAVE_DEBUG_KMEMLEAK
+	select HAVE_DMA_ATTRS
 	select HAVE_DYNAMIC_FTRACE
 	select HAVE_DYNAMIC_FTRACE_WITH_REGS
 	select HAVE_FTRACE_MCOUNT_RECORD
@@ -580,7 +582,6 @@ config QDIO
 
 menuconfig PCI
 	bool "PCI support"
-	select HAVE_DMA_ATTRS
 	select PCI_MSI
 	help
 	  Enable PCI support.
diff --git a/arch/s390/include/asm/device.h b/arch/s390/include/asm/device.h
index d8f9872..4a9f35e 100644
--- a/arch/s390/include/asm/device.h
+++ b/arch/s390/include/asm/device.h
@@ -3,5 +3,9 @@
  *
  * This file is released under the GPLv2
  */
-#include <asm-generic/device.h>
+struct dev_archdata {
+	struct dma_map_ops *dma_ops;
+};
 
+struct pdev_archdata {
+};
diff --git a/arch/s390/include/asm/dma-mapping.h b/arch/s390/include/asm/dma-mapping.h
index b3fd54d..cb05f5c 100644
--- a/arch/s390/include/asm/dma-mapping.h
+++ b/arch/s390/include/asm/dma-mapping.h
@@ -11,11 +11,13 @@
 
 #define DMA_ERROR_CODE		(~(dma_addr_t) 0x0)
 
-extern struct dma_map_ops s390_dma_ops;
+extern struct dma_map_ops s390_pci_dma_ops;
 
 static inline struct dma_map_ops *get_dma_ops(struct device *dev)
 {
-	return &s390_dma_ops;
+	if (dev && dev->archdata.dma_ops)
+		return dev->archdata.dma_ops;
+	return &dma_noop_ops;
 }
 
 static inline void dma_cache_sync(struct device *dev, void *vaddr, size_t size,
diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c
index 7ef12a3..fa41605 100644
--- a/arch/s390/pci/pci.c
+++ b/arch/s390/pci/pci.c
@@ -649,6 +649,7 @@ int pcibios_add_device(struct pci_dev *pdev)
 
 	zdev->pdev = pdev;
 	pdev->dev.groups = zpci_attr_groups;
+	pdev->dev.archdata.dma_ops = &s390_pci_dma_ops;
 	zpci_map_resources(pdev);
 
 	for (i = 0; i < PCI_BAR_COUNT; i++) {
diff --git a/arch/s390/pci/pci_dma.c b/arch/s390/pci/pci_dma.c
index 37505b8..ea39c3f 100644
--- a/arch/s390/pci/pci_dma.c
+++ b/arch/s390/pci/pci_dma.c
@@ -495,7 +495,7 @@ static int __init dma_debug_do_init(void)
 }
 fs_initcall(dma_debug_do_init);
 
-struct dma_map_ops s390_dma_ops = {
+struct dma_map_ops s390_pci_dma_ops = {
 	.alloc		= s390_dma_alloc,
 	.free		= s390_dma_free,
 	.map_sg		= s390_dma_map_sg,
@@ -506,7 +506,7 @@ struct dma_map_ops s390_dma_ops = {
 	.is_phys	= 0,
 	/* dma_supported is unconditionally true without a callback */
 };
-EXPORT_SYMBOL_GPL(s390_dma_ops);
+EXPORT_SYMBOL_GPL(s390_pci_dma_ops);
 
 static int __init s390_iommu_setup(char *str)
 {
-- 
2.4.3

Re: [PATCH 3/3] s390/dma: Allow per device dma ops

[Cornelia Huck]

On Tue,  3 Nov 2015 12:54:39 +0100
Christian Borntraeger <borntraeger@de.ibm.com> wrote:

> As virtio-ccw now has dma ops, we can no longer default to the PCI ones.
> Make use of dev_archdata to keep the dma_ops per device. The pci devices
> now use that to override the default, and the default is changed to use
> the noop ops for everything that is not PCI. To compile without PCI
> support we also have to enable the DMA api with virtio.

Not only with virtio, but generally, right?

> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> Reviewed-by: Joerg Roedel <jroedel@suse.de>
> Acked-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
> ---
>  arch/s390/Kconfig                   | 3 ++-
>  arch/s390/include/asm/device.h      | 6 +++++-
>  arch/s390/include/asm/dma-mapping.h | 6 ++++--
>  arch/s390/pci/pci.c                 | 1 +
>  arch/s390/pci/pci_dma.c             | 4 ++--
>  5 files changed, 14 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
> index 1d57000..04f0e02 100644
> --- a/arch/s390/Kconfig
> +++ b/arch/s390/Kconfig
> @@ -113,6 +113,7 @@ config S390
>  	select GENERIC_FIND_FIRST_BIT
>  	select GENERIC_SMP_IDLE_THREAD
>  	select GENERIC_TIME_VSYSCALL
> +	select HAS_DMA
>  	select HAVE_ALIGNED_STRUCT_PAGE if SLUB
>  	select HAVE_ARCH_AUDITSYSCALL
>  	select HAVE_ARCH_EARLY_PFN_TO_NID
> @@ -124,6 +125,7 @@ config S390
>  	select HAVE_CMPXCHG_DOUBLE
>  	select HAVE_CMPXCHG_LOCAL
>  	select HAVE_DEBUG_KMEMLEAK
> +	select HAVE_DMA_ATTRS
>  	select HAVE_DYNAMIC_FTRACE
>  	select HAVE_DYNAMIC_FTRACE_WITH_REGS
>  	select HAVE_FTRACE_MCOUNT_RECORD
> @@ -580,7 +582,6 @@ config QDIO
> 
>  menuconfig PCI
>  	bool "PCI support"
> -	select HAVE_DMA_ATTRS
>  	select PCI_MSI
>  	help
>  	  Enable PCI support.

Hm. Further down in this file, there's

config HAS_DMA                                                                  
        def_bool PCI                                                            
        select HAVE_DMA_API_DEBUG

Should we maybe select HAVE_DMA_API_DEBUG above, drop the HAS_DMA
config option and rely on not defining NO_DMA instead?

Otherwise, the patch looks good to me.

Re: [PATCH 3/3] s390/dma: Allow per device dma ops

[Christian Borntraeger]

Am 03.11.2015 um 13:26 schrieb Cornelia Huck:
> On Tue,  3 Nov 2015 12:54:39 +0100
> Christian Borntraeger <borntraeger@de.ibm.com> wrote:
> 
>> As virtio-ccw now has dma ops, we can no longer default to the PCI ones.
>> Make use of dev_archdata to keep the dma_ops per device. The pci devices
>> now use that to override the default, and the default is changed to use
>> the noop ops for everything that is not PCI. To compile without PCI
>> support we also have to enable the DMA api with virtio.
> 
> Not only with virtio, but generally, right?

Yes, will update the patch description.
> 
>> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
>> Reviewed-by: Joerg Roedel <jroedel@suse.de>
>> Acked-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
>> ---
>>  arch/s390/Kconfig                   | 3 ++-
>>  arch/s390/include/asm/device.h      | 6 +++++-
>>  arch/s390/include/asm/dma-mapping.h | 6 ++++--
>>  arch/s390/pci/pci.c                 | 1 +
>>  arch/s390/pci/pci_dma.c             | 4 ++--
>>  5 files changed, 14 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
>> index 1d57000..04f0e02 100644
>> --- a/arch/s390/Kconfig
>> +++ b/arch/s390/Kconfig
>> @@ -113,6 +113,7 @@ config S390
>>  	select GENERIC_FIND_FIRST_BIT
>>  	select GENERIC_SMP_IDLE_THREAD
>>  	select GENERIC_TIME_VSYSCALL
>> +	select HAS_DMA
>>  	select HAVE_ALIGNED_STRUCT_PAGE if SLUB
>>  	select HAVE_ARCH_AUDITSYSCALL
>>  	select HAVE_ARCH_EARLY_PFN_TO_NID
>> @@ -124,6 +125,7 @@ config S390
>>  	select HAVE_CMPXCHG_DOUBLE
>>  	select HAVE_CMPXCHG_LOCAL
>>  	select HAVE_DEBUG_KMEMLEAK
>> +	select HAVE_DMA_ATTRS
>>  	select HAVE_DYNAMIC_FTRACE
>>  	select HAVE_DYNAMIC_FTRACE_WITH_REGS
>>  	select HAVE_FTRACE_MCOUNT_RECORD
>> @@ -580,7 +582,6 @@ config QDIO
>>
>>  menuconfig PCI
>>  	bool "PCI support"
>> -	select HAVE_DMA_ATTRS
>>  	select PCI_MSI
>>  	help
>>  	  Enable PCI support.
> 
> Hm. Further down in this file, there's
> 
> config HAS_DMA                                                                  
>         def_bool PCI                                                            
>         select HAVE_DMA_API_DEBUG
> 
> Should we maybe select HAVE_DMA_API_DEBUG above, drop the HAS_DMA
> config option and rely on not defining NO_DMA instead?

Hmm, yes. That would simplify things a lot.  Right now we include
lib/Kconfig (which defines HAS_DMA) and define it ourselfes in 
arch/s390/Kconfig. WHoever comes first wins. Adding a select statement
would make this even more complicated.

Andy, I will simply send you a respin of this patch.

Re: [PATCH 3/3] s390/dma: Allow per device dma ops

[Andy Lutomirski]

On 11/05/2015 01:33 AM, Christian Borntraeger wrote:
> Am 03.11.2015 um 13:26 schrieb Cornelia Huck:
>> On Tue,  3 Nov 2015 12:54:39 +0100
>> Christian Borntraeger <borntraeger@de.ibm.com> wrote:
>>
>>> As virtio-ccw now has dma ops, we can no longer default to the PCI ones.
>>> Make use of dev_archdata to keep the dma_ops per device. The pci devices
>>> now use that to override the default, and the default is changed to use
>>> the noop ops for everything that is not PCI. To compile without PCI
>>> support we also have to enable the DMA api with virtio.
>>
>> Not only with virtio, but generally, right?
>
> Yes, will update the patch description.
>>
>>> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
>>> Reviewed-by: Joerg Roedel <jroedel@suse.de>
>>> Acked-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
>>> ---
>>>   arch/s390/Kconfig                   | 3 ++-
>>>   arch/s390/include/asm/device.h      | 6 +++++-
>>>   arch/s390/include/asm/dma-mapping.h | 6 ++++--
>>>   arch/s390/pci/pci.c                 | 1 +
>>>   arch/s390/pci/pci_dma.c             | 4 ++--
>>>   5 files changed, 14 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
>>> index 1d57000..04f0e02 100644
>>> --- a/arch/s390/Kconfig
>>> +++ b/arch/s390/Kconfig
>>> @@ -113,6 +113,7 @@ config S390
>>>   	select GENERIC_FIND_FIRST_BIT
>>>   	select GENERIC_SMP_IDLE_THREAD
>>>   	select GENERIC_TIME_VSYSCALL
>>> +	select HAS_DMA
>>>   	select HAVE_ALIGNED_STRUCT_PAGE if SLUB
>>>   	select HAVE_ARCH_AUDITSYSCALL
>>>   	select HAVE_ARCH_EARLY_PFN_TO_NID
>>> @@ -124,6 +125,7 @@ config S390
>>>   	select HAVE_CMPXCHG_DOUBLE
>>>   	select HAVE_CMPXCHG_LOCAL
>>>   	select HAVE_DEBUG_KMEMLEAK
>>> +	select HAVE_DMA_ATTRS
>>>   	select HAVE_DYNAMIC_FTRACE
>>>   	select HAVE_DYNAMIC_FTRACE_WITH_REGS
>>>   	select HAVE_FTRACE_MCOUNT_RECORD
>>> @@ -580,7 +582,6 @@ config QDIO
>>>
>>>   menuconfig PCI
>>>   	bool "PCI support"
>>> -	select HAVE_DMA_ATTRS
>>>   	select PCI_MSI
>>>   	help
>>>   	  Enable PCI support.
>>
>> Hm. Further down in this file, there's
>>
>> config HAS_DMA
>>          def_bool PCI
>>          select HAVE_DMA_API_DEBUG
>>
>> Should we maybe select HAVE_DMA_API_DEBUG above, drop the HAS_DMA
>> config option and rely on not defining NO_DMA instead?
>
> Hmm, yes. That would simplify things a lot.  Right now we include
> lib/Kconfig (which defines HAS_DMA) and define it ourselfes in
> arch/s390/Kconfig. WHoever comes first wins. Adding a select statement
> would make this even more complicated.
>
> Andy, I will simply send you a respin of this patch.
>

I'm slightly concerned that I'm going to screw this all up and apply the 
wrong version.  Could you resend the whole series with git format-patch 
-vN for some appropriate N (or similar)?

Thanks,
Andy

[PATCHv2 0/3] dma ops and virtio

[Christian Borntraeger]

here is the 2nd version of providing an DMA API for s390.

There are some attempts to unify the dma ops (Christoph) as well
as some attempts to make virtio use the dma API (Andy).

At kernel summit we concluded that we want to use the same code on all
platforms, whereever possible, so having a dummy dma_op might be the
easiest solution to keep virtio-ccw as similar as possible to
virtio-pci.Together with a fixed up patch set from Andy Lutomirski
this seems to work.  

We will also need a fixup for powerc and QEMU changes to make virtio
work with iommu on power and x86.

TODO:
- future add-on patches to also fold in x86 no iommu
	- dma_mask
	- checking?
- make compilation of dma-noop dependent on something

v1->v2:
- initial testing
- always use dma_noop_ops if device has no private dma_ops
- get rid of setup in virtio_ccw,kvm_virtio
- set CONFIG_HAS_DMA(ATTRS) for virtio (fixes compile for !PCI)
- rename s390_dma_ops to s390_pci_dma_ops

Christian Borntraeger (3):
  Provide simple noop dma ops
  alpha: use common noop dma ops
  s390/dma: Allow per device dma ops

 arch/alpha/kernel/pci-noop.c        | 46 ++--------------------
 arch/s390/Kconfig                   |  3 +-
 arch/s390/include/asm/device.h      |  6 ++-
 arch/s390/include/asm/dma-mapping.h |  6 ++-
 arch/s390/pci/pci.c                 |  1 +
 arch/s390/pci/pci_dma.c             |  4 +-
 include/linux/dma-mapping.h         |  2 +
 lib/Makefile                        |  2 +-
 lib/dma-noop.c                      | 77 +++++++++++++++++++++++++++++++++++++
 9 files changed, 98 insertions(+), 49 deletions(-)
 create mode 100644 lib/dma-noop.c

-- 
2.4.3

[PATCH 3/3] s390/dma: Allow per device dma ops

[Christian Borntraeger]

As virtio-ccw now has dma ops, we can no longer default to the PCI ones.
Make use of dev_archdata to keep the dma_ops per device. The pci devices
now use that to override the default, and the default is changed to use
the noop ops for everything that is not PCI. To compile without PCI
support we also have to enable the DMA api with virtio.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
---
 arch/s390/Kconfig                   | 3 ++-
 arch/s390/include/asm/device.h      | 6 +++++-
 arch/s390/include/asm/dma-mapping.h | 6 ++++--
 arch/s390/pci/pci.c                 | 1 +
 arch/s390/pci/pci_dma.c             | 4 ++--
 5 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 1d57000..04f0e02 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -113,6 +113,7 @@ config S390
 	select GENERIC_FIND_FIRST_BIT
 	select GENERIC_SMP_IDLE_THREAD
 	select GENERIC_TIME_VSYSCALL
+	select HAS_DMA
 	select HAVE_ALIGNED_STRUCT_PAGE if SLUB
 	select HAVE_ARCH_AUDITSYSCALL
 	select HAVE_ARCH_EARLY_PFN_TO_NID
@@ -124,6 +125,7 @@ config S390
 	select HAVE_CMPXCHG_DOUBLE
 	select HAVE_CMPXCHG_LOCAL
 	select HAVE_DEBUG_KMEMLEAK
+	select HAVE_DMA_ATTRS
 	select HAVE_DYNAMIC_FTRACE
 	select HAVE_DYNAMIC_FTRACE_WITH_REGS
 	select HAVE_FTRACE_MCOUNT_RECORD
@@ -580,7 +582,6 @@ config QDIO
 
 menuconfig PCI
 	bool "PCI support"
-	select HAVE_DMA_ATTRS
 	select PCI_MSI
 	help
 	  Enable PCI support.
diff --git a/arch/s390/include/asm/device.h b/arch/s390/include/asm/device.h
index d8f9872..4a9f35e 100644
--- a/arch/s390/include/asm/device.h
+++ b/arch/s390/include/asm/device.h
@@ -3,5 +3,9 @@
  *
  * This file is released under the GPLv2
  */
-#include <asm-generic/device.h>
+struct dev_archdata {
+	struct dma_map_ops *dma_ops;
+};
 
+struct pdev_archdata {
+};
diff --git a/arch/s390/include/asm/dma-mapping.h b/arch/s390/include/asm/dma-mapping.h
index b3fd54d..cb05f5c 100644
--- a/arch/s390/include/asm/dma-mapping.h
+++ b/arch/s390/include/asm/dma-mapping.h
@@ -11,11 +11,13 @@
 
 #define DMA_ERROR_CODE		(~(dma_addr_t) 0x0)
 
-extern struct dma_map_ops s390_dma_ops;
+extern struct dma_map_ops s390_pci_dma_ops;
 
 static inline struct dma_map_ops *get_dma_ops(struct device *dev)
 {
-	return &s390_dma_ops;
+	if (dev && dev->archdata.dma_ops)
+		return dev->archdata.dma_ops;
+	return &dma_noop_ops;
 }
 
 static inline void dma_cache_sync(struct device *dev, void *vaddr, size_t size,
diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c
index 7ef12a3..fa41605 100644
--- a/arch/s390/pci/pci.c
+++ b/arch/s390/pci/pci.c
@@ -649,6 +649,7 @@ int pcibios_add_device(struct pci_dev *pdev)
 
 	zdev->pdev = pdev;
 	pdev->dev.groups = zpci_attr_groups;
+	pdev->dev.archdata.dma_ops = &s390_pci_dma_ops;
 	zpci_map_resources(pdev);
 
 	for (i = 0; i < PCI_BAR_COUNT; i++) {
diff --git a/arch/s390/pci/pci_dma.c b/arch/s390/pci/pci_dma.c
index 37505b8..ea39c3f 100644
--- a/arch/s390/pci/pci_dma.c
+++ b/arch/s390/pci/pci_dma.c
@@ -495,7 +495,7 @@ static int __init dma_debug_do_init(void)
 }
 fs_initcall(dma_debug_do_init);
 
-struct dma_map_ops s390_dma_ops = {
+struct dma_map_ops s390_pci_dma_ops = {
 	.alloc		= s390_dma_alloc,
 	.free		= s390_dma_free,
 	.map_sg		= s390_dma_map_sg,
@@ -506,7 +506,7 @@ struct dma_map_ops s390_dma_ops = {
 	.is_phys	= 0,
 	/* dma_supported is unconditionally true without a callback */
 };
-EXPORT_SYMBOL_GPL(s390_dma_ops);
+EXPORT_SYMBOL_GPL(s390_pci_dma_ops);
 
 static int __init s390_iommu_setup(char *str)
 {
-- 
2.4.3

Re: [PATCH 3/3] s390/dma: Allow per device dma ops

[Joerg Roedel]

On Fri, Oct 30, 2015 at 02:20:37PM +0100, Christian Borntraeger wrote:
> As virtio-ccw now has dma ops, we can no longer default to the PCI ones.
> Make use of dev_archdata to keep the dma_ops per device. The pci devices
> now use that to override the default, and the default is changed to use
> the noop ops for everything that is not PCI. To compile without PCI
> support we also have to enable the DMA api with virtio.
> 
> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> ---
>  arch/s390/Kconfig                   | 3 ++-
>  arch/s390/include/asm/device.h      | 6 +++++-
>  arch/s390/include/asm/dma-mapping.h | 6 ++++--
>  arch/s390/pci/pci.c                 | 1 +
>  arch/s390/pci/pci_dma.c             | 4 ++--
>  5 files changed, 14 insertions(+), 6 deletions(-)

Reviewed-by: Joerg Roedel <jroedel@suse.de>

Re: [PATCH 3/3] s390/dma: Allow per device dma ops

[Sebastian Ott]

On Fri, 30 Oct 2015, Christian Borntraeger wrote:

> As virtio-ccw now has dma ops, we can no longer default to the PCI ones.
> Make use of dev_archdata to keep the dma_ops per device. The pci devices
> now use that to override the default, and the default is changed to use
> the noop ops for everything that is not PCI. To compile without PCI
> support we also have to enable the DMA api with virtio.
> 
> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

Acked-by: Sebastian Ott <sebott@linux.vnet.ibm.com>