[PATCH v2 1/8] dma-debug: Allow multiple invocations of overlapping entries

Leon Romanovsky
2026-03-11T19:09:05Z

From: Leon Romanovsky <leonro@nvidia.com>

Repeated DMA mappings with DMA_ATTR_CPU_CACHE_CLEAN trigger the
following splat. This prevents using the attribute in cases where a DMA
region is shared and reused more than seven times.

------------[ cut here ]------------
DMA-API: exceeded 7 overlapping mappings of cacheline 0x000000000438c440
WARNING: kernel/dma/debug.c:467 at add_dma_entry+0x219/0x280, CPU#4: ibv_rc_pingpong/1644
Modules linked in: xt_conntrack xt_MASQUERADE nf_conntrack_netlink nfnetlink iptable_nat nf_nat xt_addrtype br_netfilter rpcsec_gss_krb5 auth_rpcgss oid_registry overlay mlx5_fwctl zram zsmalloc mlx5_ib fuse rpcrdma rdma_ucm ib_uverbs ib_iser libiscsi scsi_transport_iscsi ib_umad rdma_cm ib_ipoib iw_cm ib_cm mlx5_core ib_core
CPU: 4 UID: 2733 PID: 1644 Comm: ibv_rc_pingpong Not tainted 6.19.0+ #129 PREEMPT
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
RIP: 0010:add_dma_entry+0x221/0x280
Code: c0 0f 84 f2 fe ff ff 83 e8 01 89 05 6d 99 11 01 e9 e4 fe ff ff 0f 8e 1f ff ff ff 48 8d 3d 07 ef 2d 01 be 07 00 00 00 48 89 e2 <67> 48 0f b9 3a e9 06 ff ff ff 48 c7 c7 98 05 2b 82 c6 05 72 92 28
RSP: 0018:ff1100010e657970 EFLAGS: 00010002
RAX: 0000000000000007 RBX: ff1100010234eb00 RCX: 0000000000000000
RDX: ff1100010e657970 RSI: 0000000000000007 RDI: ffffffff82678660
RBP: 000000000438c440 R08: 0000000000000228 R09: 0000000000000000
R10: 00000000000001be R11: 000000000000089d R12: 0000000000000800
R13: 00000000ffffffef R14: 0000000000000202 R15: ff1100010234eb00
FS: 00007fb15f3f6740(0000) GS:ff110008dcc19000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb15f32d3a0 CR3: 0000000116f59001 CR4: 0000000000373eb0
Call Trace:
<TASK>
debug_dma_map_sg+0x1b4/0x390
__dma_map_sg_attrs+0x6d/0x1a0
dma_map_sgtable+0x19/0x30
ib_umem_get+0x284/0x3b0 [ib_uverbs]
mlx5_ib_reg_user_mr+0x68/0x2a0 [mlx5_ib]
ib_uverbs_reg_mr+0x17f/0x2a0 [ib_uverbs]
ib_uverbs_handler_UVERBS_METHOD_INVOKE_WRITE+0xc2/0x130 [ib_uverbs]
ib_uverbs_cmd_verbs+0xa0b/0xae0 [ib_uverbs]
? ib_uverbs_handler_UVERBS_METHOD_QUERY_PORT_SPEED+0xe0/0xe0 [ib_uverbs]
? mmap_region+0x7a/0xb0
? do_mmap+0x3b8/0x5c0
ib_uverbs_ioctl+0xa7/0x110 [ib_uverbs]
__x64_sys_ioctl+0x14f/0x8b0
? ksys_mmap_pgoff+0xc5/0x190
do_syscall_64+0x8c/0xbf0
entry_SYSCALL_64_after_hwframe+0x4b/0x53
RIP: 0033:0x7fb15f5e4eed
Code: 04 25 28 00 00 00 48 89 45 c8 31 c0 48 8d 45 10 c7 45 b0 10 00 00 00 48 89 45 b8 48 8d 45 d0 48 89 45 c0 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 1a 48 8b 45 c8 64 48 2b 04 25 28 00 00 00
RSP: 002b:00007ffe09a5c540 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ffe09a5c5d0 RCX: 00007fb15f5e4eed
RDX: 00007ffe09a5c5f0 RSI: 00000000c0181b01 RDI: 0000000000000003
RBP: 00007ffe09a5c590 R08: 0000000000000028 R09: 00007ffe09a5c794
R10: 0000000000000001 R11: 0000000000000246 R12: 00007ffe09a5c794
R13: 000000000000000c R14: 0000000025a49170 R15: 000000000000000c
</TASK>
---[ end trace 0000000000000000 ]---

Fixes: 61868dc55a11 ("dma-mapping: add DMA_ATTR_CPU_CACHE_CLEAN")
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
kernel/dma/debug.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c
index 86f87e43438c3..be207be749968 100644
--- a/kernel/dma/debug.c
+++ b/kernel/dma/debug.c
@@ -453,7 +453,7 @@ static int active_cacheline_set_overlap(phys_addr_t cln, int overlap)
return overlap;
}

-static void active_cacheline_inc_overlap(phys_addr_t cln)
+static void active_cacheline_inc_overlap(phys_addr_t cln, bool is_cache_clean)
{
int overlap = active_cacheline_read_overlap(cln);

@@ -462,7 +462,7 @@ static void active_cacheline_inc_overlap(phys_addr_t cln)
/* If we overflowed the overlap counter then we're potentially
* leaking dma-mappings.
*/
- WARN_ONCE(overlap > ACTIVE_CACHELINE_MAX_OVERLAP,
+ WARN_ONCE(!is_cache_clean && overlap > ACTIVE_CACHELINE_MAX_OVERLAP,
pr_fmt("exceeded %d overlapping mappings of cacheline %pa\n"),
ACTIVE_CACHELINE_MAX_OVERLAP, &cln);
}
@@ -495,7 +495,7 @@ static int active_cacheline_insert(struct dma_debug_entry *entry,
if (rc == -EEXIST) {
struct dma_debug_entry *existing;

- active_cacheline_inc_overlap(cln);
+ active_cacheline_inc_overlap(cln, entry->is_cache_clean);
existing = radix_tree_lookup(&dma_active_cacheline, cln);
/* A lookup failure here after we got -EEXIST is unexpected. */
WARN_ON(!existing);

--
2.53.0