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

Nuno Das Neves
2025-03-01T00:38:23Z

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
>>