[Xen-devel] identify a Xen PV domU to fix devmem_is_allowed

[Olaf Hering <olaf@xxxxxxxxx>]

What is the correct way to identify a Xen PV domU in the kenrel?
devmem_is_allowed() used to disable access to pages < 256 in domU.
With pvops this check was removed, or never ported forward.

Would this change be the correct fix?

+++ b/arch/x86/mm/init.c
@@ -637,7 +637,7 @@ void __init init_mem_mapping(void)
 int devmem_is_allowed(unsigned long pagenr)
 {
        if (pagenr < 256)
-               return 1;
+               return !xen_pv_domain();
        if (iomem_is_exclusive(pagenr << PAGE_SHIFT))
                return 0;
        if (!page_is_ram(pagenr))

Olaf

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