[kernel,RFC,1/3] powerpc/pseries/iommu: Allow dynamic window to start from zero

Message ID 20180725095032.2196-2-aik@ozlabs.ru
State RFC
Headers show
Series
  • powerpc/pseries/iommu: GPU coherent memory pass through
Related show

Commit Message

Alexey Kardashevskiy July 25, 2018, 9:50 a.m.
At the moment the kernel does not expect dynamic windows to ever start
at zero on a PCI bus as PAPR requires the hypervisor to create a 32bit
default window which starts from zero and the pseries kernel only
creates additional windows.

However PAPR permits removing the default window and creating another
one instead, starting from zero as well. In fact, the kernel used to
remove the default window after sha1 25ebc45b934 but this has been
reverted later.

Since there are devices capable of more than 32 bits for DMA but less than
50, and currently available hardware allows the second window only
at 1<<59, we will need to be able to create bigger windows starting from
zero. This does the initial preparation and should not cause any
behavioral changes.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
 arch/powerpc/platforms/pseries/iommu.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

Comments

David Gibson July 27, 2018, 3:42 a.m. | #1
On Wed, Jul 25, 2018 at 07:50:30PM +1000, Alexey Kardashevskiy wrote:
> At the moment the kernel does not expect dynamic windows to ever start
> at zero on a PCI bus as PAPR requires the hypervisor to create a 32bit
> default window which starts from zero and the pseries kernel only
> creates additional windows.
> 
> However PAPR permits removing the default window and creating another
> one instead, starting from zero as well. In fact, the kernel used to
> remove the default window after sha1 25ebc45b934 but this has been
> reverted later.
> 
> Since there are devices capable of more than 32 bits for DMA but less than
> 50, and currently available hardware allows the second window only
> at 1<<59, we will need to be able to create bigger windows starting from
> zero. This does the initial preparation and should not cause any
> behavioral changes.
> 
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
>  arch/powerpc/platforms/pseries/iommu.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
> index 06f0296..9ece42f 100644
> --- a/arch/powerpc/platforms/pseries/iommu.c
> +++ b/arch/powerpc/platforms/pseries/iommu.c
> @@ -53,6 +53,8 @@
>  
>  #include "pseries.h"
>  
> +#define DDW_INVALID_OFFSET	((uint64_t)-1)
> +
>  static struct iommu_table_group *iommu_pseries_alloc_group(int node)
>  {
>  	struct iommu_table_group *table_group;
> @@ -844,7 +846,7 @@ static u64 find_existing_ddw(struct device_node *pdn)
>  {
>  	struct direct_window *window;
>  	const struct dynamic_dma_window_prop *direct64;
> -	u64 dma_addr = 0;
> +	u64 dma_addr = DDW_INVALID_OFFSET;
>  
>  	spin_lock(&direct_window_list_lock);
>  	/* check if we already created a window and dupe that config if so */
> @@ -992,7 +994,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
>  	mutex_lock(&direct_window_init_mutex);
>  
>  	dma_addr = find_existing_ddw(pdn);
> -	if (dma_addr != 0)
> +	if (dma_addr != DDW_INVALID_OFFSET)
>  		goto out_unlock;
>  
>  	/*
> @@ -1228,7 +1230,7 @@ static int dma_set_mask_pSeriesLP(struct device *dev, u64 dma_mask)
>  		}
>  		if (pdn && PCI_DN(pdn)) {
>  			dma_offset = enable_ddw(pdev, pdn);
> -			if (dma_offset != 0) {
> +			if (dma_offset != DDW_INVALID_OFFSET) {
>  				dev_info(dev, "Using 64-bit direct DMA at offset %llx\n", dma_offset);
>  				set_dma_offset(dev, dma_offset);
>  				set_dma_ops(dev, &dma_nommu_ops);

Patch

diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
index 06f0296..9ece42f 100644
--- a/arch/powerpc/platforms/pseries/iommu.c
+++ b/arch/powerpc/platforms/pseries/iommu.c
@@ -53,6 +53,8 @@ 
 
 #include "pseries.h"
 
+#define DDW_INVALID_OFFSET	((uint64_t)-1)
+
 static struct iommu_table_group *iommu_pseries_alloc_group(int node)
 {
 	struct iommu_table_group *table_group;
@@ -844,7 +846,7 @@  static u64 find_existing_ddw(struct device_node *pdn)
 {
 	struct direct_window *window;
 	const struct dynamic_dma_window_prop *direct64;
-	u64 dma_addr = 0;
+	u64 dma_addr = DDW_INVALID_OFFSET;
 
 	spin_lock(&direct_window_list_lock);
 	/* check if we already created a window and dupe that config if so */
@@ -992,7 +994,7 @@  static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 	mutex_lock(&direct_window_init_mutex);
 
 	dma_addr = find_existing_ddw(pdn);
-	if (dma_addr != 0)
+	if (dma_addr != DDW_INVALID_OFFSET)
 		goto out_unlock;
 
 	/*
@@ -1228,7 +1230,7 @@  static int dma_set_mask_pSeriesLP(struct device *dev, u64 dma_mask)
 		}
 		if (pdn && PCI_DN(pdn)) {
 			dma_offset = enable_ddw(pdev, pdn);
-			if (dma_offset != 0) {
+			if (dma_offset != DDW_INVALID_OFFSET) {
 				dev_info(dev, "Using 64-bit direct DMA at offset %llx\n", dma_offset);
 				set_dma_offset(dev, dma_offset);
 				set_dma_ops(dev, &dma_nommu_ops);