Re: [Xen-devel] [PATCH 2/2 v2] x86/acpi: Improve suspend and resume process for Zhaoxin CPU

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 25.04.19 at 15:25, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 25/04/2019 14:21, Jan Beulich wrote:
>>>>> On 19.04.19 at 10:50, <fionali-oc@xxxxxxxxxxx> wrote:
>>> --- a/xen/arch/x86/x86_64/traps.c
>>> +++ b/xen/arch/x86/x86_64/traps.c
>>> @@ -334,7 +334,8 @@ void subarch_percpu_traps_init(void)
>>>                                     (unsigned long)lstar_enter);
>>>      stub_va += offset;
>>>  
>>> -    if ( boot_cpu_data.x86_vendor & (X86_VENDOR_INTEL | 
>>> X86_VENDOR_CENTAUR) 
> )
>>> +    if ( boot_cpu_data.x86_vendor &
>>> +        (X86_VENDOR_INTEL | X86_VENDOR_CENTAUR | X86_VENDOR_SHANGHAI) )
>>>      {
>>>          /* SYSENTER entry. */
>>>          wrmsrl(MSR_IA32_SYSENTER_ESP, stack_bottom);
>> How is this hunk related to the title of the change? I think the
>> title wants to be adjusted.
>>
>> Furthermore for all of the changes done, wouldn't we better
>> switch to use cpu_has_sep? init_amd() as well as default_init()
>> already clear this flag. Andrew, thoughts?
> 
> I wondered exactly that after queuing this patch, but didn't get around
> to experimenting.
> 
> We have to be a little careful with the ordering of operations. 
> cpu_has_sep is visible in CPUID but needs clobbering in AMD/Hygon before
> cpu_has_sep is safe to use (although for the MSRs, it should be safe).

trap_init() (and hence percpu_traps_init()) runs after, in
particular, init_speculation_mitigations(), which means all
feature collection and massaging must have happened. So
unless you explicitly say otherwise, I'd like to ask FionaLi
to submit a v2 with that change (and with the other cosmetic
adjustments carried out).

Jan



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