linux-kernel - [PATCH 5.10 38/55] xsk: Clear page contiguity bit when unmapping pool

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Message-Id: <20220711090542.881801977@linuxfoundation.org>
Date:   Mon, 11 Jul 2022 11:07:26 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ivan Malov <ivan.malov@...etlabs.ru>,
        Daniel Borkmann <daniel@...earbox.net>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.10 38/55] xsk: Clear page contiguity bit when unmapping pool

From: Ivan Malov <ivan.malov@...etlabs.ru>

[ Upstream commit 512d1999b8e94a5d43fba3afc73e774849674742 ]

When a XSK pool gets mapped, xp_check_dma_contiguity() adds bit 0x1
to pages' DMA addresses that go in ascending order and at 4K stride.

The problem is that the bit does not get cleared before doing unmap.
As a result, a lot of warnings from iommu_dma_unmap_page() are seen
in dmesg, which indicates that lookups by iommu_iova_to_phys() fail.

Fixes: 2b43470add8c ("xsk: Introduce AF_XDP buffer allocation API")
Signed-off-by: Ivan Malov <ivan.malov@...etlabs.ru>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Acked-by: Magnus Karlsson <magnus.karlsson@...el.com>
Link: https://lore.kernel.org/bpf/20220628091848.534803-1-ivan.malov@oktetlabs.ru
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/xdp/xsk_buff_pool.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c
index 2ef6f926610e..e63a285a9856 100644
--- a/net/xdp/xsk_buff_pool.c
+++ b/net/xdp/xsk_buff_pool.c
@@ -318,6 +318,7 @@ static void __xp_dma_unmap(struct xsk_dma_map *dma_map, unsigned long attrs)
 	for (i = 0; i < dma_map->dma_pages_cnt; i++) {
 		dma = &dma_map->dma_pages[i];
 		if (*dma) {
+			*dma &= ~XSK_NEXT_PG_CONTIG_MASK;
 			dma_unmap_page_attrs(dma_map->dev, *dma, PAGE_SIZE,
 					     DMA_BIDIRECTIONAL, attrs);
 			*dma = 0;
-- 
2.35.1