page_pool: devmem support

Convert netmem to be a union of struct page and struct netmem. Overload
the LSB of struct netmem* to indicate that it's a net_iov, otherwise
it's a page.

Currently these entries in struct page are rented by the page_pool and
used exclusively by the net stack:

struct {
	unsigned long pp_magic;
	struct page_pool *pp;
	unsigned long _pp_mapping_pad;
	unsigned long dma_addr;
	atomic_long_t pp_ref_count;
};

Mirror these (and only these) entries into struct net_iov and implement
netmem helpers that can access these common fields regardless of
whether the underlying type is page or net_iov.

Implement checks for net_iov in netmem helpers which delegate to mm
APIs, to ensure net_iov are never passed to the mm stack.

Signed-off-by: Mina Almasry <almasrymina@google.com>
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Link: https://patch.msgid.link/20240910171458.219195-6-almasrymina@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 26 insertions, 0 deletions

diff --git a/net/core/page_pool_priv.h b/net/core/page_pool_priv.h
index 90665d40f1eb..d602c1e728c2 100644
--- a/net/core/page_pool_priv.h
+++ b/net/core/page_pool_priv.h
@@ -3,10 +3,36 @@
 #ifndef __PAGE_POOL_PRIV_H
 #define __PAGE_POOL_PRIV_H
 
+#include <net/page_pool/helpers.h>
+
+#include "netmem_priv.h"
+
 s32 page_pool_inflight(const struct page_pool *pool, bool strict);
 
 int page_pool_list(struct page_pool *pool);
 void page_pool_detached(struct page_pool *pool);
 void page_pool_unlist(struct page_pool *pool);
 
+static inline bool
+page_pool_set_dma_addr_netmem(netmem_ref netmem, dma_addr_t addr)
+{
+	if (PAGE_POOL_32BIT_ARCH_WITH_64BIT_DMA) {
+		netmem_set_dma_addr(netmem, addr >> PAGE_SHIFT);
+
+		/* We assume page alignment to shave off bottom bits,
+		 * if this "compression" doesn't work we need to drop.
+		 */
+		return addr != (dma_addr_t)netmem_get_dma_addr(netmem)
+				       << PAGE_SHIFT;
+	}
+
+	netmem_set_dma_addr(netmem, addr);
+	return false;
+}
+
+static inline bool page_pool_set_dma_addr(struct page *page, dma_addr_t addr)
+{
+	return page_pool_set_dma_addr_netmem(page_to_netmem(page), addr);
+}
+
 #endif