netdev - [PATCH RFC net-next 15/34] page_pool: add inline helper to sync VA for device (for XDP

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Date: Sat, 23 Dec 2023 03:55:35 +0100
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>
Cc: Alexander Lobakin <aleksander.lobakin@...el.com>,
	Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
	Michal Kubiak <michal.kubiak@...el.com>,
	Larysa Zaremba <larysa.zaremba@...el.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Willem de Bruijn <willemdebruijn.kernel@...il.com>,
	intel-wired-lan@...ts.osuosl.org,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH RFC net-next 15/34] page_pool: add inline helper to sync VA for device (for XDP_TX)

Drivers using Page Pool for Rx buffers do the same pattern on XDP_TX:
syncing-DMA-for-device and obtaining DMA address for &xdp_buff they
are sending.
Add a helper for that to be able to do that in one call in the drivers.
I explicitly added `bool compound` argument and set it to false by
default: only a few drivers, if any, uses high-order pages with Page
Pool, so losing cycles on compound_head() looks suboptimal. Drivers
can always call the underscored version if needed (for example, pass
pool->p.order as the last argument -- will always work).

Signed-off-by: Alexander Lobakin <aleksander.lobakin@...el.com>
---
 include/net/page_pool/helpers.h | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h
index 873631c79ab1..99dc825b03a5 100644
--- a/include/net/page_pool/helpers.h
+++ b/include/net/page_pool/helpers.h
@@ -397,6 +397,38 @@ static inline bool page_pool_set_dma_addr(struct page *page, dma_addr_t addr)
 	return false;
 }
 
+static inline dma_addr_t __page_pool_dma_sync_va_for_device(const void *va,
+							    u32 dma_sync_size,
+							    bool compound)
+{
+	const struct page_pool *pool;
+	const struct page *page;
+	dma_addr_t addr;
+	u32 offset;
+
+	if (unlikely(compound)) {
+		page = virt_to_head_page(va);
+		offset = va - page_address(page);
+	} else {
+		page = virt_to_page(va);
+		offset = offset_in_page(va);
+	}
+
+	addr = page_pool_get_dma_addr(page) + offset;
+	pool = page->pp;
+
+	dma_sync_single_for_device(pool->p.dev, addr, dma_sync_size,
+				   page_pool_get_dma_dir(pool));
+
+	return addr;
+}
+
+static inline dma_addr_t page_pool_dma_sync_va_for_device(const void *va,
+							  u32 dma_sync_size)
+{
+	return __page_pool_dma_sync_va_for_device(va, dma_sync_size, false);
+}
+
 /**
  * page_pool_dma_sync_for_cpu - sync Rx page for CPU after it's written by HW
  * @pool: &page_pool the @page belongs to
-- 
2.43.0