Re: [PATCH v2 06/27] ocxl: Tally up the LPC memory on a link & allow it to be mapped

[Frederic Barrat]

Le 03/12/2019 Ã 04:46, Alastair D'Silva a ÃcritÂ:
> From: Alastair D'Silva <alastair@xxxxxxxxxxx>
>
> Tally up the LPC memory on an OpenCAPI link & allow it to be mapped
>
> Signed-off-by: Alastair D'Silva <alastair@xxxxxxxxxxx>
> ---
>   drivers/misc/ocxl/core.c          | 10 ++++++
>   drivers/misc/ocxl/link.c          | 60 +++++++++++++++++++++++++++++++
>   drivers/misc/ocxl/ocxl_internal.h | 33 +++++++++++++++++
>   3 files changed, 103 insertions(+)
>
> diff --git a/drivers/misc/ocxl/core.c b/drivers/misc/ocxl/core.c
> index b7a09b21ab36..2531c6cf19a0 100644
> --- a/drivers/misc/ocxl/core.c
> +++ b/drivers/misc/ocxl/core.c
> @@ -230,8 +230,18 @@ static int configure_afu(struct ocxl_afu *afu, u8 afu_idx, struct pci_dev *dev)
>   	if (rc)
>   		goto err_free_pasid;
>   
> +	if (afu->config.lpc_mem_size || afu->config.special_purpose_mem_size) {
> +		rc = ocxl_link_add_lpc_mem(afu->fn->link, afu->config.lpc_mem_offset,
> +					   afu->config.lpc_mem_size +
> +					   afu->config.special_purpose_mem_size);
> +		if (rc)
> +			goto err_free_mmio;
> +	}
> +
>   	return 0;
>   
> +err_free_mmio:
> +	unmap_mmio_areas(afu);
>   err_free_pasid:
>   	reclaim_afu_pasid(afu);
>   err_free_actag:
> diff --git a/drivers/misc/ocxl/link.c b/drivers/misc/ocxl/link.c
> index 58d111afd9f6..d8503f0dc6ec 100644
> --- a/drivers/misc/ocxl/link.c
> +++ b/drivers/misc/ocxl/link.c
> @@ -84,6 +84,11 @@ struct ocxl_link {
>   	int dev;
>   	atomic_t irq_available;
>   	struct spa *spa;
> +	struct mutex lpc_mem_lock;
> +	u64 lpc_mem_sz; /* Total amount of LPC memory presented on the link */
> +	u64 lpc_mem;
> +	int lpc_consumers;
> +
>   	void *platform_data;
>   };
>   static struct list_head links_list = LIST_HEAD_INIT(links_list);
> @@ -396,6 +401,8 @@ static int alloc_link(struct pci_dev *dev, int PE_mask, struct ocxl_link **out_l
>   	if (rc)
>   		goto err_spa;
>   
> +	mutex_init(&link->lpc_mem_lock);
> +
>   	/* platform specific hook */
>   	rc = pnv_ocxl_spa_setup(dev, link->spa->spa_mem, PE_mask,
>   				&link->platform_data);
> @@ -711,3 +718,56 @@ void ocxl_link_free_irq(void *link_handle, int hw_irq)
>   	atomic_inc(&link->irq_available);
>   }
>   EXPORT_SYMBOL_GPL(ocxl_link_free_irq);
> +
> +int ocxl_link_add_lpc_mem(void *link_handle, u64 offset, u64 size)
> +{
> +	struct ocxl_link *link = (struct ocxl_link *) link_handle;
> +
> +	// Check for overflow
> +	if (offset > (offset + size))
> +		return -EINVAL;
> +
> +	mutex_lock(&link->lpc_mem_lock);
> +	link->lpc_mem_sz = max(link->lpc_mem_sz, offset + size);
> +
> +	mutex_unlock(&link->lpc_mem_lock);
> +
> +	return 0;
> +}
> +
> +u64 ocxl_link_lpc_map(void *link_handle, struct pci_dev *pdev)
> +{
> +	struct ocxl_link *link = (struct ocxl_link *) link_handle;
> +	u64 lpc_mem;
> +
> +	mutex_lock(&link->lpc_mem_lock);
> +	if (link->lpc_mem) {
> +		lpc_mem = link->lpc_mem;
> +
> +		link->lpc_consumers++;
> +		mutex_unlock(&link->lpc_mem_lock);
> +		return lpc_mem;
> +	}
> +
> +	link->lpc_mem = pnv_ocxl_platform_lpc_setup(pdev, link->lpc_mem_sz);
> +	if (link->lpc_mem)
> +		link->lpc_consumers++;


So if we fail to setup the lpc access in opal, we don't increment 
link->lpc_consumers and we shouldn't call ocxl_link_lpc_release(). Is 
that always true? Risk is to trigger the warning in 
ocxl_link_lpc_release(). So maybe we should check link->lpc_mem first in 
ocxl_link_lpc_release() and exit early if no memory is mapped. It would 
probably avoid hitting the WARN on an error path for example.

   Fred


> +	lpc_mem = link->lpc_mem;
> +	mutex_unlock(&link->lpc_mem_lock);
> +
> +	return lpc_mem;
> +}
> +
> +void ocxl_link_lpc_release(void *link_handle, struct pci_dev *pdev)
> +{
> +	struct ocxl_link *link = (struct ocxl_link *) link_handle;
> +
> +	mutex_lock(&link->lpc_mem_lock);
> +	WARN_ON(--link->lpc_consumers < 0);
> +	if (link->lpc_consumers == 0) {
> +		pnv_ocxl_platform_lpc_release(pdev);
> +		link->lpc_mem = 0;
> +	}
> +
> +	mutex_unlock(&link->lpc_mem_lock);
> +}
> diff --git a/drivers/misc/ocxl/ocxl_internal.h b/drivers/misc/ocxl/ocxl_internal.h
> index 97415afd79f3..20b417e00949 100644
> --- a/drivers/misc/ocxl/ocxl_internal.h
> +++ b/drivers/misc/ocxl/ocxl_internal.h
> @@ -141,4 +141,37 @@ int ocxl_irq_offset_to_id(struct ocxl_context *ctx, u64 offset);
>   u64 ocxl_irq_id_to_offset(struct ocxl_context *ctx, int irq_id);
>   void ocxl_afu_irq_free_all(struct ocxl_context *ctx);
>   
> +/**
> + * ocxl_link_add_lpc_mem() - Increment the amount of memory required by an OpenCAPI link
> + *
> + * @link_handle: The OpenCAPI link handle
> + * @offset: The offset of the memory to add
> + * @size: The amount of memory to increment by
> + *
> + * Return 0 on success, negative on overflow
> + */
> +int ocxl_link_add_lpc_mem(void *link_handle, u64 offset, u64 size);
> +
> +/**
> + * ocxl_link_lpc_map() - Map the LPC memory for an OpenCAPI device
> + *
> + * Since LPC memory belongs to a link, the whole LPC memory available
> + * on the link bust be mapped in order to make it accessible to a device.
> + *
> + * @link_handle: The OpenCAPI link handle
> + * @pdev: A device that is on the link
> + */
> +u64 ocxl_link_lpc_map(void *link_handle, struct pci_dev *pdev);
> +
> +/**
> + * ocxl_link_lpc_release() - Release the LPC memory device for an OpenCAPI device
> + *
> + * Offlines LPC memory on an OpenCAPI link for a device. If this is the
> + * last device on the link to release the memory, unmap it from the link.
> + *
> + * @link_handle: The OpenCAPI link handle
> + * @pdev: A device that is on the link
> + */
> +void ocxl_link_lpc_release(void *link_handle, struct pci_dev *pdev);
> +
>   #endif /* _OCXL_INTERNAL_H_ */