4 files changed, 45 insertions, 10 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 4609e81dbc37..cff672da2486 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -596,9 +596,6 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                         is selected automatically. Check
                         Documentation/kdump/kdump.txt for further details.
 
-        crashkernel_low=size[KMG]
-                        [KNL, x86] parts under 4G.
-
         crashkernel=range1:size1[,range2:size2,...][@offset]
                         [KNL] Same as above, but depends on the memory
                         in the running system. The syntax of range is
@@ -606,6 +603,17 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                         a memory unit (amount[KMG]). See also
                         Documentation/kdump/kdump.txt for an example.
 
+        crashkernel_low=size[KMG]
+                        [KNL, x86_64] range under 4G. When crashkernel= is
+                        passed, kernel allocate physical memory region
+                        above 4G, that cause second kernel crash on system
+                        that require some amount of low memory, e.g. swiotlb
+                        requires at least 64M+32K low memory.  Kernel would
+                        try to allocate 72M below 4G automatically.
+                        This one let user to specify own low range under 4G
+                        for second kernel instead.
+                        0: to disable low allocation.
+
         cs89x0_dma=     [HW,NET]
                         Format: <dma>
 
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;
         }
diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index 2de42f9401d2..a5ffd32642fd 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -25,6 +25,7 @@ extern int swiotlb_force;
 extern void swiotlb_init(int verbose);
 int swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose);
 extern unsigned long swiotlb_nr_tbl(void);
+unsigned long swiotlb_size_or_default(void);
 extern int swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs);
 
 /*
diff --git a/lib/swiotlb.c b/lib/swiotlb.c
index bfe02b8fc55b..d23762e6652c 100644
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -105,9 +105,9 @@ setup_io_tlb_npages(char *str)
         if (!strcmp(str, "force"))
                 swiotlb_force = 1;
 
-        return 1;
+        return 0;
 }
-__setup("swiotlb=", setup_io_tlb_npages);
+early_param("swiotlb", setup_io_tlb_npages);
 /* make io_tlb_overflow tunable too? */
 
 unsigned long swiotlb_nr_tbl(void)
@@ -115,6 +115,18 @@ unsigned long swiotlb_nr_tbl(void)
         return io_tlb_nslabs;
 }
 EXPORT_SYMBOL_GPL(swiotlb_nr_tbl);
+
+/* default to 64MB */
+#define IO_TLB_DEFAULT_SIZE (64UL<<20)
+unsigned long swiotlb_size_or_default(void)
+{
+        unsigned long size;
+
+        size = io_tlb_nslabs << IO_TLB_SHIFT;
+
+        return size ? size : (IO_TLB_DEFAULT_SIZE);
+}
+
 /* Note that this doesn't work with highmem page */
 static dma_addr_t swiotlb_virt_to_bus(struct device *hwdev,
                                       volatile void *address)
@@ -188,8 +200,7 @@ int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
 void  __init
 swiotlb_init(int verbose)
 {
-        /* default to 64MB */
-        size_t default_size = 64UL<<20;
+        size_t default_size = IO_TLB_DEFAULT_SIZE;
         unsigned char *vstart;
         unsigned long bytes;