[Xen-devel] [PATCH for-4.13] x86/AMD: unbreak CPU hotplug on AMD systems without RstrFpErrPtrs

[Igor Druzhinin <igor.druzhinin@xxxxxxxxxx>]

If the feature is not present Xen will try to force X86_BUG_FPU_PTRS
feature at CPU identification time. This is especially noticeable in
PV-shim that usually hotplugs its vCPUs. We either need to restrict this
action for boot CPU only or allow secondary CPUs to modify
forced CPU capabilities at runtime. Choose the latter accounting
for potential microcode asymmetry between the boot and secondary CPUs.

Signed-off-by: Igor Druzhinin <igor.druzhinin@xxxxxxxxxx>
---
Justification for 4.13 - PV-shim is effectively broken on such a system.
---
 xen/arch/x86/cpu/common.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/cpu/common.c b/xen/arch/x86/cpu/common.c
index e5ad17d..4293075 100644
--- a/xen/arch/x86/cpu/common.c
+++ b/xen/arch/x86/cpu/common.c
@@ -54,7 +54,7 @@ static unsigned int forced_caps[NCAPINTS];
 
 DEFINE_PER_CPU(bool, full_gdt_loaded);
 
-void __init setup_clear_cpu_cap(unsigned int cap)
+void setup_clear_cpu_cap(unsigned int cap)
 {
        const uint32_t *dfs;
        unsigned int i;
@@ -83,7 +83,7 @@ void __init setup_clear_cpu_cap(unsigned int cap)
        }
 }
 
-void __init setup_force_cpu_cap(unsigned int cap)
+void setup_force_cpu_cap(unsigned int cap)
 {
        if (__test_and_set_bit(cap, forced_caps))
                return;
-- 
2.7.4


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