[PATCH 2/3] PCI/P2PMEM: introduce pci_p2pdma_align_size API

[Max Gurtovoy <mgurtovoy@nvidia.com>]

The mhp layer has alignment restrictions that may cause a failure in
adding a large P2PMEM that has non-aligned number of pages. The new API
pci_p2pdma_align_size will align the P2PMEM size to be inline with the
mhp restrictions.

Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
---
 drivers/pci/p2pdma.c       | 23 +++++++++++++++++++++++
 include/linux/pci-p2pdma.h |  5 +++++
 2 files changed, 28 insertions(+)

diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index 196382630363..d232bc4ada2b 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -220,6 +220,29 @@ int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, size_t size,
 }
 EXPORT_SYMBOL_GPL(pci_p2pdma_add_resource);
 
+/**
+ * pci_p2pdma_align_size - align p2p memory size
+ * @size: size of the initial memory to align before adding.
+ *
+ * The size will be aligned according to mph alignment rules. This function
+ * should be called before adding new p2pdma resource since non-aligned memory
+ * will not be added.
+ */
+size_t pci_p2pdma_align_size(size_t size)
+{
+	unsigned int min_align, nr_pages;
+
+	min_align = mhp_get_min_align();
+	nr_pages = size >> PAGE_SHIFT;
+	if (!IS_ALIGNED(nr_pages, min_align)) {
+		nr_pages = ALIGN_DOWN(nr_pages, min_align);
+		size = nr_pages << PAGE_SHIFT;
+	}
+
+	return size;
+}
+EXPORT_SYMBOL_GPL(pci_p2pdma_align_size);
+
 /*
  * Note this function returns the parent PCI device with a
  * reference taken. It is the caller's responsibility to drop
diff --git a/include/linux/pci-p2pdma.h b/include/linux/pci-p2pdma.h
index 8318a97c9c61..33a8fce52bec 100644
--- a/include/linux/pci-p2pdma.h
+++ b/include/linux/pci-p2pdma.h
@@ -38,6 +38,7 @@ int pci_p2pdma_enable_store(const char *page, struct pci_dev **p2p_dev,
 			    bool *use_p2pdma);
 ssize_t pci_p2pdma_enable_show(char *page, struct pci_dev *p2p_dev,
 			       bool use_p2pdma);
+size_t pci_p2pdma_align_size(size_t size);
 #else /* CONFIG_PCI_P2PDMA */
 static inline int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar,
 		size_t size, u64 offset)
@@ -105,6 +106,10 @@ static inline ssize_t pci_p2pdma_enable_show(char *page,
 {
 	return sprintf(page, "none\n");
 }
+static inline size_t pci_p2pdma_align_size(size_t size)
+{
+	return 0;
+}
 #endif /* CONFIG_PCI_P2PDMA */
 
 
-- 
2.18.1