[xen stable-4.16] x86/retpoline: split retpoline compiler support into separate option

[patchbot@xxxxxxx]

commit 0caab659704bb0944a62f7535f3c726f5db922c5
Author:     Roger Pau Monné <roger.pau@xxxxxxxxxx>
AuthorDate: Thu Mar 31 10:54:08 2022 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Mar 31 10:54:08 2022 +0200

    x86/retpoline: split retpoline compiler support into separate option
    
    Keep the previous option as a way to signal generic retpoline support
    regardless of the underlying compiler, while introducing a new
    CC_HAS_INDIRECT_THUNK that signals whether the underlying compiler
    supports retpoline.
    
    No functional change intended.
    
    Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    master commit: e245bc154300b5d0367b64e8b937c9d1da508ad3
    master date: 2022-02-21 18:17:56 +0000
---
 xen/arch/x86/Kconfig |  6 +++++-
 xen/arch/x86/arch.mk | 10 ++++++----
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig
index ef72e7821b..e20e53edfc 100644
--- a/xen/arch/x86/Kconfig
+++ b/xen/arch/x86/Kconfig
@@ -32,9 +32,13 @@ config ARCH_DEFCONFIG
        string
        default "arch/x86/configs/x86_64_defconfig"
 
-config INDIRECT_THUNK
+config CC_HAS_INDIRECT_THUNK
        def_bool $(cc-option,-mindirect-branch-register)
 
+config INDIRECT_THUNK
+       def_bool y
+       depends on CC_HAS_INDIRECT_THUNK
+
 config HAS_AS_CET_SS
        # binutils >= 2.29 or LLVM >= 6
        def_bool $(as-instr,wrssq %rax$(comma)0;setssbsy)
diff --git a/xen/arch/x86/arch.mk b/xen/arch/x86/arch.mk
index 456e5d5c1a..abb55b4408 100644
--- a/xen/arch/x86/arch.mk
+++ b/xen/arch/x86/arch.mk
@@ -41,10 +41,12 @@ CFLAGS += -mno-red-zone -fpic
 # SSE setup for variadic function calls.
 CFLAGS += -mno-sse $(call cc-option,$(CC),-mskip-rax-setup)
 
-# Compile with thunk-extern, indirect-branch-register if avaiable.
-CFLAGS-$(CONFIG_INDIRECT_THUNK) += -mindirect-branch=thunk-extern
-CFLAGS-$(CONFIG_INDIRECT_THUNK) += -mindirect-branch-register
-CFLAGS-$(CONFIG_INDIRECT_THUNK) += -fno-jump-tables
+ifeq ($(CONFIG_INDIRECT_THUNK),y)
+# Compile with gcc thunk-extern, indirect-branch-register if available.
+CFLAGS-$(CONFIG_CC_IS_GCC) += -mindirect-branch=thunk-extern
+CFLAGS-$(CONFIG_CC_IS_GCC) += -mindirect-branch-register
+CFLAGS-$(CONFIG_CC_IS_GCC) += -fno-jump-tables
+endif
 
 ifdef CONFIG_XEN_IBT
 # Force -fno-jump-tables to work around
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.16