[xen stable-4.20] x86/amd: Stop updating the Zenbleed mitigation dynamically

[patchbot@xxxxxxx]

commit f5b36e23ec452cec8b748e24c6e381ff8aeb6b95
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Wed Dec 3 11:44:12 2025 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Dec 3 11:44:12 2025 +0100

    x86/amd: Stop updating the Zenbleed mitigation dynamically
    
    This was potentially helpful when the chickenbit was the only mitigation and
    microcode had not been released, but that was two years ago.
    
    Zenbleed microcode has been avaialble since December 2023, and the 
subsequent
    Entrysign signature vulnerability means that firmware updates block 
OS-loading
    and more OS-loadable microcode will be produced for Zen2.
    
    i.e. the Zenbleed fix is not going to appear at runtime these days.
    
    No practical change.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
    master commit: 5cd1ac15756ed7d9175685a3d16fc23fc86b3db4
    master date: 2025-11-27 18:22:20 +0000
---
 xen/arch/x86/cpu/amd.c               | 2 +-
 xen/arch/x86/cpu/microcode/amd.c     | 2 --
 xen/arch/x86/include/asm/processor.h | 2 --
 3 files changed, 1 insertion(+), 5 deletions(-)

diff --git a/xen/arch/x86/cpu/amd.c b/xen/arch/x86/cpu/amd.c
index 597b0f073d..32bb5792ca 100644
--- a/xen/arch/x86/cpu/amd.c
+++ b/xen/arch/x86/cpu/amd.c
@@ -913,7 +913,7 @@ void __init detect_zen2_null_seg_behaviour(void)
 
 }
 
-void amd_check_zenbleed(void)
+static void amd_check_zenbleed(void)
 {
        const struct cpu_signature *sig = &this_cpu(cpu_sig);
        unsigned int good_rev;
diff --git a/xen/arch/x86/cpu/microcode/amd.c b/xen/arch/x86/cpu/microcode/amd.c
index 0b51796791..995a050e52 100644
--- a/xen/arch/x86/cpu/microcode/amd.c
+++ b/xen/arch/x86/cpu/microcode/amd.c
@@ -373,8 +373,6 @@ static int cf_check apply_microcode(const struct 
microcode_patch *patch,
            "microcode: CPU%u updated from revision %#x to %#x, date = 
%04x-%02x-%02x\n",
            cpu, old_rev, rev, patch->year, patch->month, patch->day);
 
-    amd_check_zenbleed();
-
     return 0;
 }
 
diff --git a/xen/arch/x86/include/asm/processor.h 
b/xen/arch/x86/include/asm/processor.h
index 1aec6691c9..98734f4d3f 100644
--- a/xen/arch/x86/include/asm/processor.h
+++ b/xen/arch/x86/include/asm/processor.h
@@ -504,8 +504,6 @@ enum ap_boot_method {
 };
 extern enum ap_boot_method ap_boot_method;
 
-void amd_check_zenbleed(void);
-
 #endif /* !__ASSEMBLY__ */
 
 #endif /* __ASM_X86_PROCESSOR_H */
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.20