Re: [PATCH] powerpc/pseries/iommu: enable_ddw incorrectly returns direct mapping for SR-IOV device.

[Madhavan Srinivasan <maddy@linux.ibm.com>]

On 10/3/23 3:16 AM, Gaurav Batra wrote:
> When a device is initialized, the driver invokes dma_supported() twice - first
> for streaming mappings followed by coherent mappings. For an SR-IOV device,
> default window is deleted and DDW created. With vPMEM enabled, TCE mappings
> are dynamically created for both vPMEM and SR-IOV device. There are no direct
> mappings.
>
> First time when dma_supported() is called with 64 bit mask, DDW is created and
> marked as dynamic window. The second time dma_supported() is called, enable_ddw()
> finds existing window for the device and incorrectly returns it as "direct mapping".
>
> This only happens when size of DDW is capable of mapping max LPAR memory.
>
> This results in streaming TCEs to not get dynamically mapped, since code incorrently
> assumes these are already pre-mapped. The adapter initially comes up but goes down
> due to EEH.

Just checked for patch submission and it is missing "Signed-off-by:"
It is good to run once with checkpatch.pl before posting to mailing list

maddy

> ---
>   arch/powerpc/platforms/pseries/iommu.c | 7 ++++---
>   1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
> index 16d93b580f61..d8b4adcef1ad 100644
> --- a/arch/powerpc/platforms/pseries/iommu.c
> +++ b/arch/powerpc/platforms/pseries/iommu.c
> @@ -914,7 +914,8 @@ static int remove_ddw(struct device_node *np, bool remove_prop, const char *win_
>   	return 0;
>   }
>
> -static bool find_existing_ddw(struct device_node *pdn, u64 *dma_addr, int *window_shift)
> +static bool find_existing_ddw(struct device_node *pdn, u64 *dma_addr, int *window_shift,
> +			      bool *direct_mapping)
>   {
>   	struct dma_win *window;
>   	const struct dynamic_dma_window_prop *dma64;
> @@ -927,6 +928,7 @@ static bool find_existing_ddw(struct device_node *pdn, u64 *dma_addr, int *windo
>   			dma64 = window->prop;
>   			*dma_addr = be64_to_cpu(dma64->dma_base);
>   			*window_shift = be32_to_cpu(dma64->window_shift);
> +			*direct_mapping = window->direct;
>   			found = true;
>   			break;
>   		}
> @@ -1270,8 +1272,7 @@ static bool enable_ddw(struct pci_dev *dev, struct device_node *pdn)
>
>   	mutex_lock(&dma_win_init_mutex);
>
> -	if (find_existing_ddw(pdn, &dev->dev.archdata.dma_offset, &len)) {
> -		direct_mapping = (len >= max_ram_len);
> +	if (find_existing_ddw(pdn, &dev->dev.archdata.dma_offset, &len, &direct_mapping)) {
>   		goto out_unlock;
>   	}
>