[xen master] xen/arm: Don't use copy_from_paddr for DTB relocation

[patchbot@xxxxxxx]

commit 2bcbcedaf9475757b3bb5104982edb2acbdd1eee
Author:     Luca Fancellu <luca.fancellu@xxxxxxx>
AuthorDate: Wed Feb 26 21:52:56 2025 +0000
Commit:     Michal Orzel <michal.orzel@xxxxxxx>
CommitDate: Tue Mar 4 08:54:45 2025 +0100

    xen/arm: Don't use copy_from_paddr for DTB relocation
    
    Currently the early stage of the Arm boot maps the DTB using
    early_fdt_map() using PAGE_HYPERVISOR_RO which is cacheable
    read-only memory, later during DTB relocation the function
    copy_from_paddr() is used to map pages in the same range on
    the fixmap but using PAGE_HYPERVISOR_WC which is non-cacheable
    read-write memory.
    
    The Arm specifications, ARM DDI0487L.a, section B2.11 "Mismatched
    memory attributes" discourage using mismatched attributes for
    aliases of the same location.
    
    Given that there is nothing preventing the relocation since the region
    is already mapped, fix that by open-coding copy_from_paddr inside
    relocate_fdt, without mapping on the fixmap.
    
    Signed-off-by: Luca Fancellu <luca.fancellu@xxxxxxx>
    Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>
---
 xen/arch/arm/setup.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
index c1f2d1b89d..ffcae900d7 100644
--- a/xen/arch/arm/setup.c
+++ b/xen/arch/arm/setup.c
@@ -237,16 +237,17 @@ void __init discard_initial_modules(void)
 }
 
 /* Relocate the FDT in Xen heap */
-static void * __init relocate_fdt(paddr_t dtb_paddr, size_t dtb_size)
+static void __init relocate_fdt(const void **dtb_vaddr, size_t dtb_size)
 {
     void *fdt = xmalloc_bytes(dtb_size);
 
     if ( !fdt )
         panic("Unable to allocate memory for relocating the Device-Tree.\n");
 
-    copy_from_paddr(fdt, dtb_paddr, dtb_size);
+    memcpy(fdt, *dtb_vaddr, dtb_size);
+    clean_dcache_va_range(fdt, dtb_size);
 
-    return fdt;
+    *dtb_vaddr = fdt;
 }
 
 void __init init_pdx(void)
@@ -362,7 +363,7 @@ void asmlinkage __init start_xen(unsigned long fdt_paddr)
     if ( acpi_disabled )
     {
         printk("Booting using Device Tree\n");
-        device_tree_flattened = relocate_fdt(fdt_paddr, fdt_size);
+        relocate_fdt(&device_tree_flattened, fdt_size);
         dt_unflatten_host_device_tree();
     }
     else
--
generated by git-patchbot for /home/xen/git/xen.git#master