2023-10-25 09:04:19

by Petr Tesarik

Subject: [PATCH] swiotlb: Do not try to allocate a TLB bigger than MAX_ORDER pages

From: Petr Tesarik <[email protected]>

When allocating a new pool at runtime, reduce the number of slabs so that
the allocation order is at most MAX_ORDER. This avoids a kernel WARNING in
__alloc_pages().

The warning is relatively benign, because the pool size is subsequently
reduced when allocation fails, but it is silly to start with a request that
is known to fail, especially since this is the default behavior if the
kernel is built with CONFIG_SWIOTLB_DYNAMIC=y and booted without any
swiotlb= parameter.

Reported-by: Ben Greear <[email protected]>
Closes: https://lore.kernel.org/netdev/[email protected]/
Fixes: 1aaa736815eb ("swiotlb: allocate a new memory pool when existing pools are full")
Signed-off-by: Petr Tesarik <[email protected]>
---
kernel/dma/swiotlb.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 01637677736f..dff067bd56b1 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -678,6 +678,11 @@ static struct io_tlb_pool *swiotlb_alloc_pool(struct device *dev,
size_t pool_size;
size_t tlb_size;

+ if (nslabs > SLABS_PER_PAGE << MAX_ORDER) {
+ nslabs = SLABS_PER_PAGE << MAX_ORDER;
+ nareas = limit_nareas(nareas, nslabs);
+ }
+
pool_size = sizeof(*pool) + array_size(sizeof(*pool->areas), nareas);
pool = kzalloc(pool_size, gfp);
if (!pool)
--
2.42.0

2023-10-25 14:27:50

by Christoph Hellwig

Subject: Re: [PATCH] swiotlb: Do not try to allocate a TLB bigger than MAX_ORDER pages

Thanks,

applied to the dma-mapping tree for Linux 6.6.