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

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Message-ID: <7de9b06d-9a32-48b5-beda-2e19b36ae9c9@linux.microsoft.com>
Date: Fri, 28 Feb 2025 16:38:19 -0800
From: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
To: Stanislav Kinsburskii <skinsburskii@...ux.microsoft.com>
Cc: linux-hyperv@...r.kernel.org, x86@...nel.org,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 linux-arch@...r.kernel.org, linux-acpi@...r.kernel.org, kys@...rosoft.com,
 haiyangz@...rosoft.com, wei.liu@...nel.org, mhklinux@...look.com,
 decui@...rosoft.com, catalin.marinas@....com, will@...nel.org,
 tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
 dave.hansen@...ux.intel.com, hpa@...or.com, daniel.lezcano@...aro.org,
 joro@...tes.org, robin.murphy@....com, arnd@...db.de,
 jinankjain@...ux.microsoft.com, muminulrussell@...il.com,
 mrathor@...ux.microsoft.com, ssengar@...ux.microsoft.com,
 apais@...ux.microsoft.com, Tianyu.Lan@...rosoft.com,
 stanislav.kinsburskiy@...il.com, gregkh@...uxfoundation.org,
 vkuznets@...hat.com, prapal@...ux.microsoft.com, muislam@...rosoft.com,
 anrayabh@...ux.microsoft.com, rafael@...nel.org, lenb@...nel.org,
 corbet@....net
Subject: Re: [PATCH v5 08/10] x86: hyperv: Add mshv_handler irq handler and
 setup function

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@...ux.microsoft.com>
>> Reviewed-by: Wei Liu <wei.liu@...nel.org>
>> Reviewed-by: Tianyu Lan <tiala@...rosoft.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@...ux.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
>>