Re: [Xen-devel] [PATCH for-4.12 v2 2/2] xen/arm: Stop relocating Xen

[Andrii Anisov <andrii.anisov@xxxxxxxxx>]

On 17.12.18 19:02, Julien Grall wrote:
> I didn't get you wrong. We are saying the same things :).
Great!

> Similarly, some version on Linux (i.e prior to 4.2) requires the DTB to within 
> 512MB from the kernel.
I've seen that restriction in the Linux for ARM64 documentation.

> > in `allocate_memory_11()` prone to end up with a wrong RAM start alignment.
> Patches are welcomed.
I see something like following as a quick WA (not even build tested):

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index d2c63a8..bf72ba9 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -223,8 +223,9 @@ fail:
  * meet these requirements directly. So instead of proceed as follows:
  *
  * We first allocate the largest allocation we can as low as we
- * can. This then becomes the first bank. This bank must be at least
- * 128MB (or dom0_mem if that is smaller).
+ * can. This then becomes the first bank. This bank is at least 128MB even if
+ * dom0 is configured for less. It is the way to get that bank 128MB aligned,
+ * what is required for 32-bit zImage.
  *
  * Then we start allocating more memory, trying to allocate the
  * largest possible size and trying smaller sizes until we
@@ -253,7 +254,7 @@ static void __init allocate_memory_11(struct domain *d,
                                       struct kernel_info *kinfo)
 {
     const unsigned int min_low_order =
-        get_order_from_bytes(min_t(paddr_t, dom0_mem, MB(128)));
+        get_order_from_bytes(MB(128));
     const unsigned int min_order = get_order_from_bytes(MB(4));
     struct page_info *pg;
     unsigned int order = get_allocation_size(kinfo->unassigned_mem);
@@ -268,6 +269,10 @@ static void __init allocate_memory_11(struct domain *d,
      */
     BUG_ON(!is_domain_direct_mapped(d));
 
+    if ( dom0_mem < MB(128))
+        printk(XENLOG_WARNING "Allocating 128MB for Domain0 with 
%"PRIu64"MB\n",
+               dom0_mem/MB(1));
+
     printk("Allocating 1:1 mappings totalling %ldMB for dom0:\n",
            /* Don't want format this as PRIpaddr (16 digit hex) */
            (unsigned long)(kinfo->unassigned_mem >> 20));


But I'm not sure if it worth to be sent, because I'm going to rewrite it soon.

--
Sincerely,
Andrii Anisov.

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