[PATCH v2 03/18] PCI: endpoint: Introduce pci_epc_mem_map()/unmap()

[Niklas Cassel]

On Sat, Mar 30, 2024 at 01:19:13PM +0900, Damien Le Moal wrote:
> Introduce the function pci_epc_mem_map() to facilitate controller memory
> address allocation and mapping to a RC PCI address region in endpoint
> function drivers.
> 
> This function first uses pci_epc_map_align() to determine the controller
> memory address alignment (offset and size) constraints. The result of
> this function is used to allocate a controller physical memory region
> using pci_epc_mem_alloc_addr() and map it to the RC PCI address
> space with pci_epc_map_addr(). Since pci_epc_map_align() may indicate
> that a mapping can be smaller than the requested size, pci_epc_mem_map()
> may only partially map the RC PCI address region specified and return
> a smaller size for the effective mapping.
> 
> The counterpart of pci_epc_mem_map() to unmap and free the controller
> memory address region is pci_epc_mem_unmap().
> 
> Both functions operate using struct pci_epc_map data structure which is
> extended to contain the physical and virtual addresses of the allocated
> controller memory. Endpoint function drivers can use struct pci_epc_map
> to implement read/write accesses within the mapped RC PCI address region
> using the ->virt_addr and ->size fields.
> 
> This commit contains contributions from Rick Wertenbroek
> <rick.wertenbroek at gmail.com>.
> 
> Signed-off-by: Damien Le Moal <dlemoal at kernel.org>
> ---
>  drivers/pci/endpoint/pci-epc-core.c | 68 +++++++++++++++++++++++++++++
>  include/linux/pci-epc.h             |  6 +++
>  2 files changed, 74 insertions(+)
> 
> diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c
> index 37758ca91d7f..0095b54bdf9e 100644
> --- a/drivers/pci/endpoint/pci-epc-core.c
> +++ b/drivers/pci/endpoint/pci-epc-core.c
> @@ -530,6 +530,74 @@ int pci_epc_map_addr(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
>  }
>  EXPORT_SYMBOL_GPL(pci_epc_map_addr);
>  
> +/**
> + * pci_epc_mem_map() - allocate and map CPU address to PCI address
> + * @epc: the EPC device on which the CPU address is to be allocated and mapped
> + * @func_no: the physical endpoint function number in the EPC device
> + * @vfunc_no: the virtual endpoint function number in the physical function
> + * @pci_addr: PCI address to which the CPU address should be mapped
> + * @size: the number of bytes to map starting from @pci_addr
> + * @map: where to return the mapping information
> + *
> + * Allocate a controller physical address region and map it to a RC PCI address
> + * region, taking into account the controller physical address mapping
> + * constraints (if any). Returns the effective size of the mapping, which may
> + * be less than @size, or a negative error code in case of error.
> + */
> +ssize_t pci_epc_mem_map(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> +			u64 pci_addr, size_t size, struct pci_epc_map *map)
> +{
> +	int ret;
> +
> +	ret = pci_epc_map_align(epc, func_no, vfunc_no, pci_addr, size, map);
> +	if (ret)
> +		return ret;
> +
> +	map->virt_base = pci_epc_mem_alloc_addr(epc, &map->phys_base,
> +						map->map_size);
> +	if (!map->virt_base)
> +		return -ENOMEM;
> +
> +	map->phys_addr = map->phys_base + map->map_ofst;
> +	map->virt_addr = map->virt_base + map->map_ofst;
> +
> +	ret = pci_epc_map_addr(epc, func_no, vfunc_no, map->phys_base,
> +			       map->map_pci_addr, map->map_size);
> +	if (ret) {
> +		pci_epc_mem_free_addr(epc, map->phys_base, map->virt_base,
> +				      map->map_size);
> +		return ret;
> +	}
> +
> +	return map->pci_size;

map->pci_size is of type size_t.
pci_epc_mem_map returns a type of ssize_t.

This means that on ILP32 you will truncate the result, and will only be
able to map a region of max size 2GB.

Could we perhaps change this function to return an int instead?
(0 on success). The mapped size can still be accessed in map->pci_size.


Kind regards,
Niklas

> +}
> +EXPORT_SYMBOL_GPL(pci_epc_mem_map);
> +
> +/**
> + * pci_epc_mem_unmap() - unmap from PCI address and free a CPU address region
> + * @epc: the EPC device on which the CPU address is allocated and mapped
> + * @func_no: the physical endpoint function number in the EPC device
> + * @vfunc_no: the virtual endpoint function number in the physical function
> + * @map: the mapping information
> + *
> + * Allocate and map local CPU address to a PCI address, accounting for the
> + * controller local CPU address alignment constraints.
> + */
> +void pci_epc_mem_unmap(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> +		       struct pci_epc_map *map)
> +{
> +	if (!pci_epc_function_is_valid(epc, func_no, vfunc_no))
> +		return;
> +
> +	if (!map || !map->pci_size)
> +		return;
> +
> +	pci_epc_unmap_addr(epc, func_no, vfunc_no, map->phys_base);
> +	pci_epc_mem_free_addr(epc, map->phys_base, map->virt_base,
> +			      map->map_size);
> +}
> +EXPORT_SYMBOL_GPL(pci_epc_mem_unmap);
> +
>  /**
>   * pci_epc_clear_bar() - reset the BAR
>   * @epc: the EPC device for which the BAR has to be cleared
> diff --git a/include/linux/pci-epc.h b/include/linux/pci-epc.h
> index 8cfb4aaf2628..86397a500b54 100644
> --- a/include/linux/pci-epc.h
> +++ b/include/linux/pci-epc.h
> @@ -304,4 +304,10 @@ void __iomem *pci_epc_mem_alloc_addr(struct pci_epc *epc,
>  				     phys_addr_t *phys_addr, size_t size);
>  void pci_epc_mem_free_addr(struct pci_epc *epc, phys_addr_t phys_addr,
>  			   void __iomem *virt_addr, size_t size);
> +
> +ssize_t pci_epc_mem_map(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> +			u64 pci_addr, size_t size, struct pci_epc_map *map);
> +void pci_epc_mem_unmap(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> +		       struct pci_epc_map *map);
> +
>  #endif /* __LINUX_PCI_EPC_H */
> -- 
> 2.44.0
>