linux-kernel - [PATCH 1/1] swiotlb: Fix debugfs reporting of reserved memory pools

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Date:   Thu, 13 Apr 2023 08:37:30 -0700
From:   Michael Kelley <mikelley@...rosoft.com>
To:     hch@....de, m.szyprowski@...sung.com, robin.murphy@....com,
        decui@...rosoft.com, tiala@...rosoft.com,
        petr.tesarik.ext@...wei.com, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Cc:     mikelley@...rosoft.com
Subject: [PATCH 1/1] swiotlb: Fix debugfs reporting of reserved memory pools

For io_tlb_nslabs, the debugfs code reports the correct value for a
specific reserved memory pool.  But for io_tlb_used, the value reported
is always for the default pool, not the specific reserved pool. Fix this.

Fixes: 5c850d31880e ("swiotlb: fix passing local variable to debugfs_create_ulong()")
Signed-off-by: Michael Kelley <mikelley@...rosoft.com>
---

I don't have a way to test this directly with OF reserved memory, but I
cobbled together a hack to call rmem_swiotlb_device_init() multiple times
for different size reserved pools. I verified that reserved pool debugfs entries
are created as expected and that the value of io_tlb_used is *not* the value
from the default pool.

 kernel/dma/swiotlb.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index dac42a2..db43de82 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -930,7 +930,9 @@ bool is_swiotlb_active(struct device *dev)
 
 static int io_tlb_used_get(void *data, u64 *val)
 {
-	*val = mem_used(&io_tlb_default_mem);
+	struct io_tlb_mem *mem = data;
+
+	*val = mem_used(mem);
 	return 0;
 }
 DEFINE_DEBUGFS_ATTRIBUTE(fops_io_tlb_used, io_tlb_used_get, NULL, "%llu\n");
@@ -943,7 +945,7 @@ static void swiotlb_create_debugfs_files(struct io_tlb_mem *mem,
 		return;
 
 	debugfs_create_ulong("io_tlb_nslabs", 0400, mem->debugfs, &mem->nslabs);
-	debugfs_create_file("io_tlb_used", 0400, mem->debugfs, NULL,
+	debugfs_create_file("io_tlb_used", 0400, mem->debugfs, mem,
 			&fops_io_tlb_used);
 }
 
-- 
1.8.3.1