[xen staging] x86/entry: Fix build with older toolchains

[patchbot@xxxxxxx]

commit a9fa82500818a8d8ce5f2843f1577bd2c29d088e
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Tue Apr 9 21:39:51 2024 +0100
Commit:     Stefano Stabellini <stefano.stabellini@xxxxxxx>
CommitDate: Tue Apr 9 14:25:01 2024 -0700

    x86/entry: Fix build with older toolchains
    
    Binutils older than 2.29 doesn't know INCSSPD.
    
    Fixes: 8e186f98ce0e ("x86: Use indirect calls in reset-stack 
infrastructure")
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
---
 xen/arch/x86/x86_64/entry.S | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S
index 461bbc3558..a4615e1ccb 100644
--- a/xen/arch/x86/x86_64/entry.S
+++ b/xen/arch/x86/x86_64/entry.S
@@ -650,7 +650,9 @@ FUNC(continue_pv_domain)
          * JMPed to.  Drop the return address.
          */
         add   $8, %rsp
+#ifdef CONFIG_XEN_SHSTK
         ALTERNATIVE "", "mov $2, %eax; incsspd %eax", X86_FEATURE_XEN_SHSTK
+#endif
 
         call  check_wakeup_from_wait
 ret_from_intr:
--
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