Re: [PATCH v8 2/5] PCI: endpoint: Add BAR subrange mapping support

Frank Li
2026-01-15T14:53:48Z

On Thu, Jan 15, 2026 at 05:49:25PM +0900, Koichiro Den wrote:
> Extend the PCI endpoint core to support mapping subranges within a BAR.
> Add an optional 'submap' field in struct pci_epf_bar so an endpoint
> function driver can request inbound mappings that fully cover the BAR.
>
> Introduce a new EPC feature bit, subrange_mapping, and reject submap
> requests from pci_epc_set_bar() unless the controller advertises both
> subrange_mapping and dynamic_inbound_mapping features.
>
> The submap array describes the complete BAR layout (no overlaps and no
> gaps are allowed to avoid exposing untranslated address ranges). This
> provides the generic infrastructure needed to map multiple logical
> regions into a single BAR at different offsets, without assuming a
> controller-specific inbound address translation mechanism.
>
> Signed-off-by: Koichiro Den <den@valinux.co.jp>
> ---
> drivers/pci/endpoint/pci-epc-core.c | 8 ++++++++
> include/linux/pci-epc.h | 4 ++++
> include/linux/pci-epf.h | 27 +++++++++++++++++++++++++++
> 3 files changed, 39 insertions(+)
>
> diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c
> index ca7f19cc973a..068155819c57 100644
> --- a/drivers/pci/endpoint/pci-epc-core.c
> +++ b/drivers/pci/endpoint/pci-epc-core.c
> @@ -596,6 +596,14 @@ int pci_epc_set_bar(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> if (!epc_features)
> return -EINVAL;
>
> + if (epf_bar->num_submap && !epf_bar->submap)
> + return -EINVAL;
> +
> + if (epf_bar->num_submap &&
> + !(epc_features->dynamic_inbound_mapping &&
> + epc_features->subrange_mapping))
> + return -EINVAL;
> +
> if (epc_features->bar[bar].type == BAR_RESIZABLE &&
> (epf_bar->size < SZ_1M || (u64)epf_bar->size > (SZ_128G * 1024)))
> return -EINVAL;
> diff --git a/include/linux/pci-epc.h b/include/linux/pci-epc.h
> index 4c8516756c56..c021c7af175f 100644
> --- a/include/linux/pci-epc.h
> +++ b/include/linux/pci-epc.h
> @@ -227,6 +227,9 @@ struct pci_epc_bar_desc {
> * inbound mappings for an already configured BAR
> * (i.e. allow calling pci_epc_set_bar() again
> * without first calling pci_epc_clear_bar())
> + * @subrange_mapping: indicate if the EPC device can map inbound subranges for a
> + * BAR. This feature depends on @dynamic_inbound_mapping
> + * feature.
> * @msi_capable: indicate if the endpoint function has MSI capability
> * @msix_capable: indicate if the endpoint function has MSI-X capability
> * @intx_capable: indicate if the endpoint can raise INTx interrupts
> @@ -236,6 +239,7 @@ struct pci_epc_bar_desc {
> struct pci_epc_features {
> unsigned int linkup_notifier : 1;
> unsigned int dynamic_inbound_mapping : 1;
> + unsigned int subrange_mapping : 1;
> unsigned int msi_capable : 1;
> unsigned int msix_capable : 1;
> unsigned int intx_capable : 1;
> diff --git a/include/linux/pci-epf.h b/include/linux/pci-epf.h
> index 48f68c4dcfa5..46f817da6e24 100644
> --- a/include/linux/pci-epf.h
> +++ b/include/linux/pci-epf.h
> @@ -110,6 +110,26 @@ struct pci_epf_driver {
>
> #define to_pci_epf_driver(drv) container_of_const((drv), struct pci_epf_driver, driver)
>
> +/**
> + * struct pci_epf_bar_submap - BAR subrange for inbound mapping
> + * @phys_addr: target physical/DMA address for this subrange
> + * @size: the size of the subrange to be mapped
> + *
> + * When pci_epf_bar.num_submap is >0, pci_epf_bar.submap describes the
> + * complete BAR layout. This allows an EPC driver to program multiple
> + * inbound translation windows for a single BAR when supported by the
> + * controller. The array order defines the BAR layout (submap[0] at offset
> + * 0, and each immediately follows the previous one).
> + *
> + * Note that the subranges:
> + * - must be non-overlapping
> + * - must exactly cover the BAR (i.e. no holes)

It is impossible after use 'size'. It can be removed.

> + */
> +struct pci_epf_bar_submap {
> + dma_addr_t phys_addr;
> + size_t size;
> +};
> +
> /**
> * struct pci_epf_bar - represents the BAR of EPF device
> * @phys_addr: physical address that should be mapped to the BAR
> @@ -119,6 +139,9 @@ struct pci_epf_driver {
> * requirement
> * @barno: BAR number
> * @flags: flags that are set for the BAR
> + * @num_submap: number of entries in @submap
> + * @submap: array of subrange descriptors allocated by the caller. See
> + * struct pci_epf_bar_submap for the restrictions in detail.
> */
> struct pci_epf_bar {
> dma_addr_t phys_addr;
> @@ -127,6 +150,10 @@ struct pci_epf_bar {
> size_t mem_size;
> enum pci_barno barno;
> int flags;
> +
> + /* Optional sub-range mapping */
> + unsigned int num_submap;
> + struct pci_epf_bar_submap *submap;

struct pci_epf_bar_submap submap[] __counted_by(num_submap);

Not sure if use this simplify alloc/free.

Frank
> };
>
> /**
> --
> 2.51.0
>