On 03/12/2019 10:08, Jan Beulich wrote:
> On 29.11.2019 21:01, Igor Druzhinin wrote:
>> --- 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;
> The two functions are deliberately __init, as any call to them
> post-init is not going to take system-wide effect.
Current example demonstrates the contrary. Setting X86_BUG_FPU_PTRS at
any point through the runtime of Xen will cause the safe action to start
happening.
Dropping this call on the non-boot CPUs leads to an insecure
configuration which we're perfectly capable of working around, and
therefore isn't an acceptable solution.
~Andrew
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