[PATCH v2] x86/setup: call early_reserve_memory() earlier

[Juergen Gross <jgross@xxxxxxxx>]

Commit a799c2bd29d19c565 ("x86/setup: Consolidate early memory
reservations") introduced early_reserve_memory() to do all needed
initial memblock_reserve() calls in one function. Unfortunately the
call of early_reserve_memory() is done too late for Xen dom0, as in
some cases a Xen hook called by e820__memory_setup() will need those
memory reservations to have happened already.

Move the call of early_reserve_memory() before the call of
e820__memory_setup() in order to avoid such problems.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: a799c2bd29d19c565 ("x86/setup: Consolidate early memory reservations")
Reported-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
V2:
- update comment (Jan Beulich, Boris Petkov)
- move call down in setup_arch() (Mike Galbraith)
---
 arch/x86/kernel/setup.c | 26 ++++++++++++++------------
 1 file changed, 14 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 79f164141116..40ed44ead063 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -830,6 +830,20 @@ void __init setup_arch(char **cmdline_p)
 
        x86_init.oem.arch_setup();
 
+       /*
+        * Do some memory reservations *before* memory is added to memblock, so
+        * memblock allocations won't overwrite it.
+        *
+        * After this point, everything still needed from the boot loader or
+        * firmware or kernel text should be early reserved or marked not RAM in
+        * e820. All other memory is free game.
+        *
+        * This call needs to happen before e820__memory_setup() which calls the
+        * xen_memory_setup() on Xen dom0 which relies on the fact that those
+        * early reservations have happened already.
+        */
+       early_reserve_memory();
+
        iomem_resource.end = (1ULL << boot_cpu_data.x86_phys_bits) - 1;
        e820__memory_setup();
        parse_setup_data();
@@ -876,18 +890,6 @@ void __init setup_arch(char **cmdline_p)
 
        parse_early_param();
 
-       /*
-        * Do some memory reservations *before* memory is added to
-        * memblock, so memblock allocations won't overwrite it.
-        * Do it after early param, so we could get (unlikely) panic from
-        * serial.
-        *
-        * After this point everything still needed from the boot loader or
-        * firmware or kernel text should be early reserved or marked not
-        * RAM in e820. All other memory is free game.
-        */
-       early_reserve_memory();
-
 #ifdef CONFIG_MEMORY_HOTPLUG
        /*
         * Memory used by the kernel cannot be hot-removed because Linux
-- 
2.26.2