1 files changed, 18 insertions, 3 deletions

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 90d8cc930f5e..12349202cae7 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -521,19 +521,34 @@ static void __init reserve_crashkernel_low(void)
         unsigned long long low_base = 0, low_size = 0;
         unsigned long total_low_mem;
         unsigned long long base;
+        bool auto_set = false;
         int ret;
 
         total_low_mem = memblock_mem_size(1UL<<(32-PAGE_SHIFT));
         ret = parse_crashkernel_low(boot_command_line, total_low_mem,
                                                 &low_size, &base);
-        if (ret != 0 || low_size <= 0)
-                return;
+        if (ret != 0) {
+                /*
+                 * two parts from lib/swiotlb.c:
+                 *      swiotlb size: user specified with swiotlb= or default.
+                 *      swiotlb overflow buffer: now is hardcoded to 32k.
+                 *              We round it to 8M for other buffers that
+                 *              may need to stay low too.
+                 */
+                low_size = swiotlb_size_or_default() + (8UL<<20);
+                auto_set = true;
+        } else {
+                /* passed with crashkernel_low=0 ? */
+                if (!low_size)
+                        return;
+        }
 
         low_base = memblock_find_in_range(low_size, (1ULL<<32),
                                         low_size, alignment);
 
         if (!low_base) {
-                pr_info("crashkernel low reservation failed - No suitable area found.\n");
+                if (!auto_set)
+                        pr_info("crashkernel low reservation failed - No suitable area found.\n");
 
                 return;
         }