PCI: endpoint: Retain fixed-size BAR size as well as aligned size

When allocating space for an endpoint function on a BAR with a fixed size,
the size saved in 'struct pci_epf_bar.size' should be the fixed size as
expected by pci_epc_set_bar().

However, if pci_epf_alloc_space() increased the allocation size to
accommodate iATU alignment requirements, it previously saved the larger
aligned size in .size, which broke pci_epc_set_bar().

To solve this, keep the fixed BAR size in .size and save the aligned size
in a new .aligned_size for use when deallocating it.

Fixes: 2a9a801 ("PCI: endpoint: Add support to specify alignment for buffers allocated to BARs")
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
[mani: commit message fixup]
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
[bhelgaas: more specific subject, commit log, wrap comment to match file]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Niklas Cassel <cassel@kernel.org>
Link: https://patch.msgid.link/20250424-pci-ep-size-alignment-v5-1-2d4ec2af23f5@baylibre.com

Author: jbrun3t

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 +286,18 @@ 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 +308,7 @@ 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 +317,7 @@ 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;

include/linux/pci-epf.h

@@ -114,13 +114,16 @@ 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
  * @barno: BAR number
  * @flags: flags that are set for the BAR
  */
 struct pci_epf_bar {
 	dma_addr_t	phys_addr;
 	void		*addr;
 	size_t		size;
+	size_t		aligned_size;
 	enum pci_barno	barno;
 	int		flags;
 };