Re: [PATCH v5 08/10] x86: hyperv: Add mshv_handler irq handler and setup function

[Nuno Das Neves <nunodasneves@linux.microsoft.com>]

On 2/26/2025 3:43 PM, Stanislav Kinsburskii wrote:
> On Wed, Feb 26, 2025 at 03:08:02PM -0800, Nuno Das Neves wrote:
>> This will handle SYNIC interrupts such as intercepts, doorbells, and
>> scheduling messages intended for the mshv driver.
>>
>> Signed-off-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
>> Reviewed-by: Wei Liu <wei.liu@kernel.org>
>> Reviewed-by: Tianyu Lan <tiala@microsoft.com>
>> ---
>>  arch/x86/kernel/cpu/mshyperv.c | 9 +++++++++
>>  drivers/hv/hv_common.c         | 5 +++++
>>  include/asm-generic/mshyperv.h | 1 +
>>  3 files changed, 15 insertions(+)
>>
>> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
>> index 0116d0e96ef9..616e9a5d77b4 100644
>> --- a/arch/x86/kernel/cpu/mshyperv.c
>> +++ b/arch/x86/kernel/cpu/mshyperv.c
>> @@ -107,6 +107,7 @@ void hv_set_msr(unsigned int reg, u64 value)
>>  }
>>  EXPORT_SYMBOL_GPL(hv_set_msr);
>>  
>> +static void (*mshv_handler)(void);
>>  static void (*vmbus_handler)(void);
>>  static void (*hv_stimer0_handler)(void);
>>  static void (*hv_kexec_handler)(void);
>> @@ -117,6 +118,9 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_hyperv_callback)
>>  	struct pt_regs *old_regs = set_irq_regs(regs);
>>  
>>  	inc_irq_stat(irq_hv_callback_count);
>> +	if (mshv_handler)
>> +		mshv_handler();
> 
> Can mshv_handler be defined as a weak symbol doing nothing instead
> of defining it a null pointer?
> This should allow to simplify this code and get rid of
> hv_setup_mshv_handler, which looks redundant.
> 
Interesting, I tested this and it does seems to work! It seems like
a good change, thanks.

> Reviewed-by: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
> 
>> +
>>  	if (vmbus_handler)
>>  		vmbus_handler();
>>  
>> @@ -126,6 +130,11 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_hyperv_callback)
>>  	set_irq_regs(old_regs);
>>  }
>>  
>> +void hv_setup_mshv_handler(void (*handler)(void))
>> +{
>> +	mshv_handler = handler;
>> +}
>> +
>>  void hv_setup_vmbus_handler(void (*handler)(void))
>>  {
>>  	vmbus_handler = handler;
>> diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
>> index 2763cb6d3678..f5a07fd9a03b 100644
>> --- a/drivers/hv/hv_common.c
>> +++ b/drivers/hv/hv_common.c
>> @@ -677,6 +677,11 @@ void __weak hv_remove_vmbus_handler(void)
>>  }
>>  EXPORT_SYMBOL_GPL(hv_remove_vmbus_handler);
>>  
>> +void __weak hv_setup_mshv_handler(void (*handler)(void))
>> +{
>> +}
>> +EXPORT_SYMBOL_GPL(hv_setup_mshv_handler);
>> +
>>  void __weak hv_setup_kexec_handler(void (*handler)(void))
>>  {
>>  }
>> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
>> index 1f46d19a16aa..a05f12e63ccd 100644
>> --- a/include/asm-generic/mshyperv.h
>> +++ b/include/asm-generic/mshyperv.h
>> @@ -208,6 +208,7 @@ void hv_setup_kexec_handler(void (*handler)(void));
>>  void hv_remove_kexec_handler(void);
>>  void hv_setup_crash_handler(void (*handler)(struct pt_regs *regs));
>>  void hv_remove_crash_handler(void);
>> +void hv_setup_mshv_handler(void (*handler)(void));
>>  
>>  extern int vmbus_interrupt;
>>  extern int vmbus_irq;
>> -- 
>> 2.34.1
>>