From f5b36e23ec452cec8b748e24c6e381ff8aeb6b95 Mon Sep 17 00:00:00 2001 From: Andrew Cooper Date: Wed, 3 Dec 2025 11:44:12 +0100 Subject: [PATCH] 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 Acked-by: Jan Beulich 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 */