On Tue, Apr 22, 2025 at 04:54:19PM +0200, Jerome Brunet wrote:
> When trying to allocate space for an endpoint function on a BAR with a
> fixed size, the size saved in the 'struct pci_epf_bar' should be the fixed
> size. This is expected by pci_epc_set_bar().
>
> However, if the fixed_size is smaller that the alignment, the size saved
> in the 'struct pci_epf_bar' matches the alignment and it is a problem for
> pci_epc_set_bar().
>
> To solve this, continue to allocate space that match the iATU alignment
> requirement, saving it as .aligned_size, then save the size that matches
> what is present in the BAR.
>
> Fixes: 2a9a801620ef ("PCI: endpoint: Add support to specify alignment for buffers allocated to BARs")
> Signed-off-by: Jerome Brunet <jbrunet@xxxxxxxxxxxx>
> ---
> drivers/pci/endpoint/pci-epf-core.c | 21 ++++++++++++++-------
> include/linux/pci-epf.h | 3 +++
> 2 files changed, 17 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/pci/endpoint/pci-epf-core.c b/drivers/pci/endpoint/pci-epf-core.c
> index 394395c7f8decfa2010469655a4bd58a002993fd..982db6c1fbe77653f6a74a31df5c4e997507d2d8 100644
> --- a/drivers/pci/endpoint/pci-epf-core.c
> +++ b/drivers/pci/endpoint/pci-epf-core.c
> @@ -236,12 +236,13 @@ void pci_epf_free_space(struct pci_epf *epf, void *addr, enum pci_barno bar,
> }
>
> dev = epc->dev.parent;
> - dma_free_coherent(dev, epf_bar[bar].size, addr,
> + dma_free_coherent(dev, epf_bar[bar].aligned_size, addr,
> epf_bar[bar].phys_addr);
>
> epf_bar[bar].phys_addr = 0;
> epf_bar[bar].addr = NULL;
> epf_bar[bar].size = 0;
> + epf_bar[bar].aligned_size = 0;
> epf_bar[bar].barno = 0;
> epf_bar[bar].flags = 0;
> }
> @@ -264,7 +265,7 @@ void *pci_epf_alloc_space(struct pci_epf *epf, size_t size, enum pci_barno bar,
> enum pci_epc_interface_type type)
> {
> u64 bar_fixed_size = epc_features->bar[bar].fixed_size;
> - size_t align = epc_features->align;
> + size_t aligned_size, align = epc_features->align;
> struct pci_epf_bar *epf_bar;
> dma_addr_t phys_addr;
> struct pci_epc *epc;
> @@ -285,12 +286,17 @@ void *pci_epf_alloc_space(struct pci_epf *epf, size_t size, enum pci_barno bar,
> return NULL;
> }
> size = bar_fixed_size;
> + } else {
> + /* BAR size must be power of two */
> + size = roundup_pow_of_two(size);
> }
>
> - if (align)
> - size = ALIGN(size, align);
> - else
> - size = roundup_pow_of_two(size);
> + /*
> + * Allocate enough memory to accommodate the iATU alignment requirement.
> + * In most cases, this will be the same as .size but it might be different
> + * if, for example, the fixed size of a BAR is smaller than align.
> + */
> + aligned_size = align ? ALIGN(size, align) : size;
>
> if (type == PRIMARY_INTERFACE) {
> epc = epf->epc;
> @@ -301,7 +307,7 @@ void *pci_epf_alloc_space(struct pci_epf *epf, size_t size, enum pci_barno bar,
> }
>
> dev = epc->dev.parent;
> - space = dma_alloc_coherent(dev, size, &phys_addr, GFP_KERNEL);
> + space = dma_alloc_coherent(dev, aligned_size, &phys_addr, GFP_KERNEL);
> if (!space) {
> dev_err(dev, "failed to allocate mem space\n");
> return NULL;
> @@ -310,6 +316,7 @@ void *pci_epf_alloc_space(struct pci_epf *epf, size_t size, enum pci_barno bar,
> epf_bar[bar].phys_addr = phys_addr;
> epf_bar[bar].addr = space;
> epf_bar[bar].size = size;
> + epf_bar[bar].aligned_size = aligned_size;
> epf_bar[bar].barno = bar;
> if (upper_32_bits(size) || epc_features->bar[bar].only_64bit)
> epf_bar[bar].flags |= PCI_BASE_ADDRESS_MEM_TYPE_64;
> diff --git a/include/linux/pci-epf.h b/include/linux/pci-epf.h
> index 879d19cebd4fc6d8df9d724e3a52fa7fbd61e535..23b0878c2665db1c21e6e83543c33149ab1e0009 100644
> --- a/include/linux/pci-epf.h
> +++ b/include/linux/pci-epf.h
> @@ -114,6 +114,8 @@ struct pci_epf_driver {
> * @phys_addr: physical address that should be mapped to the BAR
> * @addr: virtual address corresponding to the @phys_addr
> * @size: the size of the address space present in BAR
> + * @aligned_size: the size actually allocated to accommodate the iATU alignment
> + * requirement.
Nit: Since none of the other lines end with a full stop.
Perhaps add one for all lines, or continue not having it for all lines.
Regardless:
Reviewed-by: Niklas Cassel <cassel@xxxxxxxxxx>
