[xen stable-4.16] x86: also suppress use of MMX insns

[patchbot@xxxxxxx]

commit 5e3a9b45c74d51c7908f809ca3ff59f18e84ab5d
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Wed Jul 27 09:22:31 2022 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Jul 27 09:22:31 2022 +0200

    x86: also suppress use of MMX insns
    
    Passing -mno-sse alone is not enough: The compiler may still find
    (questionable) reasons to use MMX insns. In particular with gcc12 use
    of MOVD+PUNPCKLDQ+MOVQ was observed in an apparent attempt to auto-
    vectorize the storing of two adjacent zeroes, 32 bits each.
    
    Reported-by: ChrisD <chris@xxxxxxxxxxxx>
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    master commit: 6fe2e39a0243bddba60f83b77b972a5922d25eb8
    master date: 2022-07-20 15:48:49 +0200
---
 xen/arch/x86/arch.mk | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/arch.mk b/xen/arch/x86/arch.mk
index 976ac5aafe..27272f767a 100644
--- a/xen/arch/x86/arch.mk
+++ b/xen/arch/x86/arch.mk
@@ -37,9 +37,9 @@ $(call as-option-add,CFLAGS,CC,\
 
 CFLAGS += -mno-red-zone -fpic
 
-# Xen doesn't use SSE interally.  If the compiler supports it, also skip the
-# SSE setup for variadic function calls.
-CFLAGS += -mno-sse $(call cc-option,$(CC),-mskip-rax-setup)
+# Xen doesn't use MMX or SSE interally.  If the compiler supports it, also skip
+# the SSE setup for variadic function calls.
+CFLAGS += -mno-mmx -mno-sse $(call cc-option,$(CC),-mskip-rax-setup)
 
 ifeq ($(CONFIG_INDIRECT_THUNK),y)
 # Compile with gcc thunk-extern, indirect-branch-register if available.
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.16