On 6/18/2025 10:02 PM, Xin Li wrote:
>> diff --git a/arch/x86/entry/entry_64_fred.S b/arch/x86/entry/entry_64_fred.S
>> index 29c5c32c16c3..1c9c6e036233 100644
>> --- a/arch/x86/entry/entry_64_fred.S
>> +++ b/arch/x86/entry/entry_64_fred.S
>> @@ -93,7 +93,7 @@ SYM_FUNC_START(asm_fred_entry_from_kvm)
>> * +--------+-----------------+
>> */
>> push $0 /* Reserved, must be 0 */
>> - push $0 /* Event data, 0 for IRQ/NMI */
>> + push %rsi /* Event data for NMI */
>
> Maybe a bit more accurate?
>
Actually, I am wondering if it might be better to make it less precise
than it is right now. How about
/* Event data passed in by the caller */
The problem with having precise comments for a generic implementation is
that the caller might get updated, but we would forget to update this
comment since nothing in this function needs to change.
> /* Event data, NMI-source bitmap only so far */
>
>> push %rdi /* fred_ss handed in by the caller */
>> push %rbp
>> pushf
...
>> /* Must be called from noinstr code, thus __always_inline */
>> -static __always_inline void fred_nmi_from_kvm(void)
>> +static __always_inline void fred_nmi_from_kvm(unsigned long edata)
>> {
>> struct fred_ss ss = {
>> .ss = __KERNEL_DS,
>> @@ -83,7 +83,7 @@ static __always_inline void fred_nmi_from_kvm(void)
>> .lm = 1,
>> };
>>
>> - asm_fred_entry_from_kvm(ss);
>> + asm_fred_entry_from_kvm(ss, edata);
>> }
>>
>> static inline void fred_irq_from_kvm(unsigned int vector)
>> @@ -95,7 +95,8 @@ static inline void fred_irq_from_kvm(unsigned int vector)
>> .lm = 1,
>> };
>>
>> - asm_fred_entry_from_kvm(ss);
>> + /* Event data is always zero for IRQ */
>
> /* Event data not used for IRQ thus 0 */
Event data "not used" might imply that the architecture provides
something, but the kernel is choosing to not use it. There is no event
data for IRQ, right?
I want to say that the event data for IRQ has to be zero until the
architecture changes — Similar to the /* Reserved, must be 0 */ comment
in asm_fred_entry_from_kvm().
