xen/arm: Allocate memory for dom0 from the bottom with the 1:1 Workaround

On Linux, the option CONFIG_ARM_PATCH_PHYS_VIRT (by default enabled) allows
the Kernel to be loaded anywhere (or nearly) by patching the translation
pv<->virt at boot time.

The current solution in Linux assuming that the delta physical address -
virtual address is always negative. A positive delta will destroy all the
optimisation to modify only a part of the translation instruction (add/sub).

By default, Xen is allocating memory from the top of memory and then
goes down. To avoid booting issue with Linux, we must allocate memory
from the bottom (ie starting from 0).

Signed-off-by: Julien Grall <julien.grall@linaro.org>
Acked-by: Ian Campbell <ian.campbell@citrix.com>

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 4f9132794595d9fe51055be266b57157823915be..4e1badf3fad9eac7d80d1927b682a4dee872cc8e 100644 (file)
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -70,12 +70,19 @@ static int set_memory_reg_11(struct domain *d, struct kernel_info *kinfo,
     int reg_size = dt_cells_to_size(dt_n_addr_cells(np) + dt_n_size_cells(np));
     paddr_t start;
     paddr_t size;
-    struct page_info *pg;
+    struct page_info *pg = NULL;
     unsigned int order = get_order_from_bytes(dom0_mem);
     int res;
     paddr_t spfn;
+    unsigned int bits;
+
+    for ( bits = PAGE_SHIFT + 1; bits < PADDR_BITS; bits++ )
+    {
+        pg = alloc_domheap_pages(d, order, MEMF_bits(bits));
+        if ( pg != NULL )
+            break;
+    }
 
-    pg = alloc_domheap_pages(d, order, 0);
     if ( !pg )
         panic("Failed to allocate contiguous memory for dom0\n");