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Re: [Xen-devel] [PATCH v2 08/10] xen/arm: keep track of reserved-memory regions

Hi Stefano,

On 30/04/2019 22:02, Stefano Stabellini wrote:
As we parse the device tree in Xen, keep track of the reserved-memory
regions as they need special treatment (follow-up patches will make use
of the stored information.)

Reuse process_memory_node to add reserved-memory regions to the
bootinfo.reserved_mem array. Remove the warning if there is no reg in
process_memory_node because it is a normal condition for

And it is not a normal condition for /memory... So your argument here is not sufficient for me to not keep the warning here for /memory.

Rather than trying to re-purpose process_memory_node, I would prefer if you move out the parsing of "reg" and then provide 2 functions (one for /memory and one for /reserved-memory).

The parsing function will return an error if "reg" is not present, but it can be ignored by /reserved-memory and a warning is added for /memory.

Signed-off-by: Stefano Stabellini <stefanos@xxxxxxxxxx>


Not done: create an e820-like structure on ARM.

Changes in v2:
- call process_memory_node from process_reserved_memory_node to avoid
  xen/arch/arm/bootfdt.c      | 30 ++++++++++++++++++++++--------
  xen/include/asm-arm/setup.h |  1 +
  2 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/xen/arch/arm/bootfdt.c b/xen/arch/arm/bootfdt.c
index b6600ab..9355a6e 100644
--- a/xen/arch/arm/bootfdt.c
+++ b/xen/arch/arm/bootfdt.c
@@ -135,6 +135,8 @@ static int __init process_memory_node(const void *fdt, int 
      const __be32 *cell;
      paddr_t start, size;
      u32 reg_cells = address_cells + size_cells;
+    struct meminfo *mem;
+    bool reserved = (bool)data;
if ( address_cells < 1 || size_cells < 1 )
@@ -143,29 +145,39 @@ static int __init process_memory_node(const void *fdt, 
int node,
          return 0;
+ if ( reserved )
+        mem = &bootinfo.reserved_mem;
+    else
+        mem = &bootinfo.mem;
      prop = fdt_get_property(fdt, node, "reg", NULL);
      if ( !prop )
-    {
-        printk("fdt: node `%s': missing `reg' property\n", name);
          return 0;
-    }
cell = (const __be32 *)prop->data;
      banks = fdt32_to_cpu(prop->len) / (reg_cells * sizeof (u32));
- for ( i = 0; i < banks && bootinfo.mem.nr_banks < NR_MEM_BANKS; i++ )
+    for ( i = 0; i < banks && mem->nr_banks < NR_MEM_BANKS; i++ )

As I pointed out on v1, this is pretty fragile. While ignoring /memory bank is fine if we have no more space, for /reserved-region this may mean using them in Xen allocator with the consequences we all know.

If you split the function properly, then you will be able to treat reserved-regions and memory differently.


Julien Grall

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