[PATCH v5 2/6] dma: swiotlb: Track whether the pool size was explicitly set

["Aneesh Kumar K.V (Arm)" <aneesh.kumar@kernel.org>]

swiotlb_adjust_size() must not override a pool size supplied through the
swiotlb= command-line parameter.

Currently, it determines whether a size was supplied by comparing
default_nslabs with IO_TLB_DEFAULT_SIZE. This fails when the user
explicitly requests the compiled-in default size, allowing the request
to be overwritten by automatic pool sizing.

Record whether swiotlb= supplied a numeric size and add
swiotlb_default_size_changed() to query that state.

Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>
---
 kernel/dma/swiotlb.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index aa19e81ae544..8f86deb25be2 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -107,6 +107,7 @@ static struct io_tlb_mem io_tlb_default_mem;
 
 static unsigned long default_nslabs = IO_TLB_DEFAULT_SIZE >> IO_TLB_SHIFT;
 static unsigned long default_nareas;
+static bool swiotlb_size_set __initdata;
 
 /**
  * struct io_tlb_area - IO TLB memory area descriptor
@@ -269,6 +270,7 @@ setup_io_tlb_npages(char *str)
 		/* avoid tail segment of size < IO_TLB_SEGSIZE */
 		default_nslabs =
 			ALIGN(simple_strtoul(str, &str, 0), IO_TLB_SEGSIZE);
+		swiotlb_size_set = true;
 	}
 	if (*str == ',')
 		++str;
@@ -304,6 +306,11 @@ unsigned long swiotlb_size_or_default(void)
 	return default_nslabs << IO_TLB_SHIFT;
 }
 
+static bool __init swiotlb_default_size_changed(void)
+{
+	return swiotlb_size_set;
+}
+
 void __init swiotlb_adjust_size(unsigned long size)
 {
 	/*
@@ -311,7 +318,7 @@ void __init swiotlb_adjust_size(unsigned long size)
 	 * architectures such as those supporting memory encryption to
 	 * adjust/expand SWIOTLB size for their use.
 	 */
-	if (default_nslabs != IO_TLB_DEFAULT_SIZE >> IO_TLB_SHIFT)
+	if (swiotlb_default_size_changed())
 		return;
 
 	default_nslabs = swiotlb_aligned_nslabs(size);
-- 
2.43.0