[RFC PATCH v8 04/14] swiotlb: Map the buffer if it was unmapped by XPFO

[Khalid Aziz <khalid.aziz@oracle.com>]

From: Juerg Haefliger <juerg.haefliger@canonical.com>

v6: * guard against lookup_xpfo() returning NULL

CC: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Juerg Haefliger <juerg.haefliger@canonical.com>
Signed-off-by: Tycho Andersen <tycho@docker.com>
Reviewed-by: Khalid Aziz <khalid.aziz@oracle.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 include/linux/xpfo.h |  4 ++++
 kernel/dma/swiotlb.c |  3 ++-
 mm/xpfo.c            | 15 +++++++++++++++
 3 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/include/linux/xpfo.h b/include/linux/xpfo.h
index b15234745fb4..cba37ffb09b1 100644
--- a/include/linux/xpfo.h
+++ b/include/linux/xpfo.h
@@ -36,6 +36,8 @@ void xpfo_kunmap(void *kaddr, struct page *page);
 void xpfo_alloc_pages(struct page *page, int order, gfp_t gfp);
 void xpfo_free_pages(struct page *page, int order);
 
+bool xpfo_page_is_unmapped(struct page *page);
+
 #else /* !CONFIG_XPFO */
 
 static inline void xpfo_kmap(void *kaddr, struct page *page) { }
@@ -43,6 +45,8 @@ static inline void xpfo_kunmap(void *kaddr, struct page *page) { }
 static inline void xpfo_alloc_pages(struct page *page, int order, gfp_t gfp) { }
 static inline void xpfo_free_pages(struct page *page, int order) { }
 
+static inline bool xpfo_page_is_unmapped(struct page *page) { return false; }
+
 #endif /* CONFIG_XPFO */
 
 #endif /* _LINUX_XPFO_H */
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 045930e32c0e..820a54b57491 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -396,8 +396,9 @@ static void swiotlb_bounce(phys_addr_t orig_addr, phys_addr_t tlb_addr,
 {
 	unsigned long pfn = PFN_DOWN(orig_addr);
 	unsigned char *vaddr = phys_to_virt(tlb_addr);
+	struct page *page = pfn_to_page(pfn);
 
-	if (PageHighMem(pfn_to_page(pfn))) {
+	if (PageHighMem(page) || xpfo_page_is_unmapped(page)) {
 		/* The buffer does not have a mapping.  Map it in and copy */
 		unsigned int offset = orig_addr & ~PAGE_MASK;
 		char *buffer;
diff --git a/mm/xpfo.c b/mm/xpfo.c
index 24b33d3c20cb..67884736bebe 100644
--- a/mm/xpfo.c
+++ b/mm/xpfo.c
@@ -221,3 +221,18 @@ void xpfo_kunmap(void *kaddr, struct page *page)
 	spin_unlock(&xpfo->maplock);
 }
 EXPORT_SYMBOL(xpfo_kunmap);
+
+bool xpfo_page_is_unmapped(struct page *page)
+{
+	struct xpfo *xpfo;
+
+	if (!static_branch_unlikely(&xpfo_inited))
+		return false;
+
+	xpfo = lookup_xpfo(page);
+	if (unlikely(!xpfo) && !xpfo->inited)
+		return false;
+
+	return test_bit(XPFO_PAGE_UNMAPPED, &xpfo->flags);
+}
+EXPORT_SYMBOL(xpfo_page_is_unmapped);
-- 
2.17.1