[PATCH 4/5] virtio: Introduce virtio_max_dma_size()

2019-01-31 Thread Joerg Roedel 
From: Joerg Roedel 

This function returns the maximum segment size for a single
dma transaction of a virtio device. The possible limit comes
from the SWIOTLB implementation in the Linux kernel, that
has an upper limit of (currently) 256kb of contiguous
memory it can map. Other DMA-API implementations might also
have limits.

Use the new dma_max_mapping_size() function to determine the
maximum mapping size when DMA-API is in use for virtio.

Reviewed-by: Konrad Rzeszutek Wilk 
Reviewed-by: Christoph Hellwig 
Signed-off-by: Joerg Roedel 
---
 drivers/virtio/virtio_ring.c | 11 +++
 include/linux/virtio.h   |  2 ++
 2 files changed, 13 insertions(+)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index cd7e755484e3..8a31c6862b2b 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -266,6 +266,17 @@ static bool vring_use_dma_api(struct virtio_device *vdev)
return false;
 }
 
+size_t virtio_max_dma_size(struct virtio_device *vdev)
+{
+   size_t max_segment_size = SIZE_MAX;
+
+   if (vring_use_dma_api(vdev))
+   max_segment_size = dma_max_mapping_size(>dev);
+
+   return max_segment_size;
+}
+EXPORT_SYMBOL_GPL(virtio_max_dma_size);
+
 static void *vring_alloc_queue(struct virtio_device *vdev, size_t size,
  dma_addr_t *dma_handle, gfp_t flag)
 {
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index fa1b5da2804e..673fe3ef3607 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -157,6 +157,8 @@ int virtio_device_freeze(struct virtio_device *dev);
 int virtio_device_restore(struct virtio_device *dev);
 #endif
 
+size_t virtio_max_dma_size(struct virtio_device *vdev);
+
 #define virtio_device_for_each_vq(vdev, vq) \
list_for_each_entry(vq, >vqs, list)
 
-- 
2.17.1

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Re: [PATCH 4/5] virtio: Introduce virtio_max_dma_size()

2019-01-30 Thread Joerg Roedel 
Hi Tom,

On Wed, Jan 30, 2019 at 03:10:29PM +, Lendacky, Thomas wrote:
> On 1/29/19 2:43 AM, Joerg Roedel wrote:

> > +size_t virtio_max_dma_size(struct virtio_device *vdev)
> > +{
> > +   size_t max_segment_size = SIZE_MAX;
> > +
> > +   if (vring_use_dma_api(vdev))
> > +   max_segment_size = dma_max_mapping_size(>dev);
> > +
> > +   return max_segment_size;
> > +}
> 
> When I build with these patches and with the virtio devices as modules I
> get a build failure. Looks like this needs an EXPORT_SYMBOL_GPL().

Thanks for pointing that out, I added the missing EXPORTs and will send
a new version shortly.

Regards,

Joerg
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Re: [PATCH 4/5] virtio: Introduce virtio_max_dma_size()

2019-01-30 Thread Lendacky, Thomas 
On 1/29/19 2:43 AM, Joerg Roedel wrote:
> From: Joerg Roedel 
> 
> This function returns the maximum segment size for a single
> dma transaction of a virtio device. The possible limit comes
> from the SWIOTLB implementation in the Linux kernel, that
> has an upper limit of (currently) 256kb of contiguous
> memory it can map. Other DMA-API implementations might also
> have limits.
> 
> Use the new dma_max_mapping_size() function to determine the
> maximum mapping size when DMA-API is in use for virtio.
> 
> Reviewed-by: Konrad Rzeszutek Wilk 
> Signed-off-by: Joerg Roedel 
> ---
>  drivers/virtio/virtio_ring.c | 10 ++
>  include/linux/virtio.h   |  2 ++
>  2 files changed, 12 insertions(+)
> 
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index cd7e755484e3..9ca3fe6af9fa 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -266,6 +266,16 @@ static bool vring_use_dma_api(struct virtio_device *vdev)
>   return false;
>  }
>  
> +size_t virtio_max_dma_size(struct virtio_device *vdev)
> +{
> + size_t max_segment_size = SIZE_MAX;
> +
> + if (vring_use_dma_api(vdev))
> + max_segment_size = dma_max_mapping_size(>dev);
> +
> + return max_segment_size;
> +}

When I build with these patches and with the virtio devices as modules I
get a build failure. Looks like this needs an EXPORT_SYMBOL_GPL().

Thanks,
Tom

> +
>  static void *vring_alloc_queue(struct virtio_device *vdev, size_t size,
> dma_addr_t *dma_handle, gfp_t flag)
>  {
> diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> index fa1b5da2804e..673fe3ef3607 100644
> --- a/include/linux/virtio.h
> +++ b/include/linux/virtio.h
> @@ -157,6 +157,8 @@ int virtio_device_freeze(struct virtio_device *dev);
>  int virtio_device_restore(struct virtio_device *dev);
>  #endif
>  
> +size_t virtio_max_dma_size(struct virtio_device *vdev);
> +
>  #define virtio_device_for_each_vq(vdev, vq) \
>   list_for_each_entry(vq, >vqs, list)
>  
> 
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Re: [PATCH 4/5] virtio: Introduce virtio_max_dma_size()

2019-01-29 Thread Christoph Hellwig 
On Tue, Jan 29, 2019 at 09:43:41AM +0100, Joerg Roedel wrote:
> From: Joerg Roedel 
> 
> This function returns the maximum segment size for a single
> dma transaction of a virtio device. The possible limit comes
> from the SWIOTLB implementation in the Linux kernel, that
> has an upper limit of (currently) 256kb of contiguous
> memory it can map. Other DMA-API implementations might also
> have limits.
> 
> Use the new dma_max_mapping_size() function to determine the
> maximum mapping size when DMA-API is in use for virtio.
> 
> Reviewed-by: Konrad Rzeszutek Wilk 
> Signed-off-by: Joerg Roedel 

Looks good,

Reviewed-by: Christoph Hellwig 
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[PATCH 4/5] virtio: Introduce virtio_max_dma_size()

2019-01-29 Thread Joerg Roedel 
From: Joerg Roedel 

This function returns the maximum segment size for a single
dma transaction of a virtio device. The possible limit comes
from the SWIOTLB implementation in the Linux kernel, that
has an upper limit of (currently) 256kb of contiguous
memory it can map. Other DMA-API implementations might also
have limits.

Use the new dma_max_mapping_size() function to determine the
maximum mapping size when DMA-API is in use for virtio.

Reviewed-by: Konrad Rzeszutek Wilk 
Signed-off-by: Joerg Roedel 
---
 drivers/virtio/virtio_ring.c | 10 ++
 include/linux/virtio.h   |  2 ++
 2 files changed, 12 insertions(+)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index cd7e755484e3..9ca3fe6af9fa 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -266,6 +266,16 @@ static bool vring_use_dma_api(struct virtio_device *vdev)
return false;
 }
 
+size_t virtio_max_dma_size(struct virtio_device *vdev)
+{
+   size_t max_segment_size = SIZE_MAX;
+
+   if (vring_use_dma_api(vdev))
+   max_segment_size = dma_max_mapping_size(>dev);
+
+   return max_segment_size;
+}
+
 static void *vring_alloc_queue(struct virtio_device *vdev, size_t size,
  dma_addr_t *dma_handle, gfp_t flag)
 {
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index fa1b5da2804e..673fe3ef3607 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -157,6 +157,8 @@ int virtio_device_freeze(struct virtio_device *dev);
 int virtio_device_restore(struct virtio_device *dev);
 #endif
 
+size_t virtio_max_dma_size(struct virtio_device *vdev);
+
 #define virtio_device_for_each_vq(vdev, vq) \
list_for_each_entry(vq, >vqs, list)
 
-- 
2.17.1

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[PATCH 4/5] virtio: Introduce virtio_max_dma_size()

2019-01-23 Thread Joerg Roedel 
From: Joerg Roedel 

This function returns the maximum segment size for a single
dma transaction of a virtio device. The possible limit comes
from the SWIOTLB implementation in the Linux kernel, that
has an upper limit of (currently) 256kb of contiguous
memory it can map. Other DMA-API implementations might also
have limits.

Use the new dma_max_mapping_size() function to determine the
maximum mapping size when DMA-API is in use for virtio.

Signed-off-by: Joerg Roedel 
---
 drivers/virtio/virtio_ring.c | 10 ++
 include/linux/virtio.h   |  2 ++
 2 files changed, 12 insertions(+)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index cd7e755484e3..9ca3fe6af9fa 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -266,6 +266,16 @@ static bool vring_use_dma_api(struct virtio_device *vdev)
return false;
 }
 
+size_t virtio_max_dma_size(struct virtio_device *vdev)
+{
+   size_t max_segment_size = SIZE_MAX;
+
+   if (vring_use_dma_api(vdev))
+   max_segment_size = dma_max_mapping_size(>dev);
+
+   return max_segment_size;
+}
+
 static void *vring_alloc_queue(struct virtio_device *vdev, size_t size,
  dma_addr_t *dma_handle, gfp_t flag)
 {
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index fa1b5da2804e..673fe3ef3607 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -157,6 +157,8 @@ int virtio_device_freeze(struct virtio_device *dev);
 int virtio_device_restore(struct virtio_device *dev);
 #endif
 
+size_t virtio_max_dma_size(struct virtio_device *vdev);
+
 #define virtio_device_for_each_vq(vdev, vq) \
list_for_each_entry(vq, >vqs, list)
 
-- 
2.17.1

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