[Xen-devel] [PATCH V2] xen/arm: domain_build: allocate lowmem for dom0 as much as possible

[van.freenix@xxxxxxxxx]

From: Peng Fan <peng.fan@xxxxxxx>

On AArch64 SoCs, some IPs may only have the capability to access
32bits address space. The physical memory assigned for Dom0 maybe
not in 4GB address space, then the IPs will not work properly.
So need to allocate memory under 4GB for Dom0.

There is no restriction that how much lowmem needs to be allocated for
Dom0. Dom0 now use 1:1 mapping, but DomU does not use 1:1 mapping,
there is no need to reserve lowmem for DomU, so allocate lowmem as much
as possible for Dom0.

Signed-off-by: Peng Fan <peng.fan@xxxxxxx>
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Cc: Julien Grall <julien.grall@xxxxxxx>
---

This patch is to resolve the issue mentioned in
https://lists.xen.org/archives/html/xen-devel/2016-09/msg00235.html

V2:
 Remove the bootargs dom0_lowmem introduced in V1.
 Following 
"https://lists.xenproject.org/archives/html/xen-devel/2016-09/msg01459.html";
 to allocate as much as possible lowmem.

 Tested results:
 (XEN) Allocating 1:1 mappings totalling 2048MB for dom0:
 (XEN) BANK[0] 0x00000088000000-0x000000f8000000 (1792MB)
 (XEN) BANK[1] 0x000009e0000000-0x000009f0000000 (256MB)
 1792M allocated in 4GB address space.

 xen/arch/arm/domain_build.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 35ab08d..0b9b85c 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -240,11 +240,11 @@ static void allocate_memory(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)));
     const unsigned int min_order = get_order_from_bytes(MB(4));
-    struct page_info *pg;
+    struct page_info *pg = NULL;
     unsigned int order = get_11_allocation_size(kinfo->unassigned_mem);
     int i;
 
-    bool_t lowmem = is_32bit_domain(d);
+    bool_t lowmem = true;
     unsigned int bits;
 
     /*
@@ -265,22 +265,28 @@ static void allocate_memory(struct domain *d, struct 
kernel_info *kinfo)
      */
     while ( order >= min_low_order )
     {
-        for ( bits = order ; bits <= (lowmem ? 32 : PADDR_BITS); bits++ )
+        for ( bits = order ; bits <= 32 ; bits++ )
         {
             pg = alloc_domheap_pages(d, order, MEMF_bits(bits));
             if ( pg != NULL )
+            {
+                if ( !insert_11_bank(d, kinfo, pg, order) )
+                    BUG(); /* Cannot fail for first bank */
+
                 goto got_bank0;
+           }
         }
         order--;
     }
 
-    panic("Unable to allocate first memory bank");
+    if ( pg == NULL )
+    {
+        printk(XENLOG_INFO "No bank has been allocated below 4GB.\n");
+        lowmem = false;
+    }
 
  got_bank0:
 
-    if ( !insert_11_bank(d, kinfo, pg, order) )
-        BUG(); /* Cannot fail for first bank */
-
     /* Now allocate more memory and fill in additional banks */
 
     order = get_11_allocation_size(kinfo->unassigned_mem);
-- 
2.6.6


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