[Xen-changelog] [xen staging] x86/boot: Simplify BSS zeroing

[patchbot@xxxxxxx]

commit c6c63b6dbffcdf32a59efa1fd6e578437fba06ff
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Wed Jan 8 13:11:13 2020 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Wed Jan 8 18:48:00 2020 +0000

    x86/boot: Simplify BSS zeroing
    
    There is no need to load a non-flat %es to zero the BSS.  Use sym_esi()
    instead, which is easier to follow, faster (avoids two segment loads) and
    doesn't require use of the stack.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/boot/head.S | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S
index 8d0ffbd1b0..c730810461 100644
--- a/xen/arch/x86/boot/head.S
+++ b/xen/arch/x86/boot/head.S
@@ -617,16 +617,12 @@ trampoline_setup:
         jnz     1f
 
         /* Initialize BSS (no nasty surprises!). */
-        mov     $sym_offs(__bss_start),%edi
-        mov     $sym_offs(__bss_end),%ecx
-        push    %fs
-        pop     %es
+        lea     sym_esi(__bss_start), %edi
+        lea     sym_esi(__bss_end), %ecx
         sub     %edi,%ecx
         xor     %eax,%eax
         shr     $2,%ecx
         rep stosl
-        push    %ds
-        pop     %es
 
 1:
         /* Interrogate CPU extended features via CPUID. */
--
generated by git-patchbot for /home/xen/git/xen.git#staging

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