linux-kernel - Re: [PATCH] arch/x86/entry_fred: don't set up KVM IRQs if KVM is disabled

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Date: Thu, 15 Feb 2024 18:10:18 -0800
From: Xin Li <xin@...or.com>
To: Sean Christopherson <seanjc@...gle.com>,
        Max Kellermann <max.kellermann@...os.com>
Cc: hpa@...or.com, x86@...nel.org, linux-kernel@...r.kernel.org,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Paolo Bonzini
 <pbonzini@...hat.com>, kvm@...r.kernel.org
Subject: Re: [PATCH] arch/x86/entry_fred: don't set up KVM IRQs if KVM is
 disabled

On 2/15/2024 11:55 AM, Sean Christopherson wrote:
> +Paolo and Stephen
> 
> FYI, there's a build failure in -next due to a collision between kvm/next and
> tip/x86/fred.  The above makes everything happy.
> 
> On Thu, Feb 15, 2024, Max Kellermann wrote:
>> When KVM is disabled, the POSTED_INTR_* macros do not exist, and the
>> build fails.
>>
>> Fixes: 14619d912b65 ("x86/fred: FRED entry/exit and dispatch code")
>> Signed-off-by: Max Kellermann <max.kellermann@...os.com>
>> ---
>>   arch/x86/entry/entry_fred.c | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/arch/x86/entry/entry_fred.c b/arch/x86/entry/entry_fred.c
>> index ac120cbdaaf2..660b7f7f9a79 100644
>> --- a/arch/x86/entry/entry_fred.c
>> +++ b/arch/x86/entry/entry_fred.c
>> @@ -114,9 +114,11 @@ static idtentry_t sysvec_table[NR_SYSTEM_VECTORS] __ro_after_init = {
>>   
>>   	SYSVEC(IRQ_WORK_VECTOR,			irq_work),
>>   
>> +#if IS_ENABLED(CONFIG_KVM)
>>   	SYSVEC(POSTED_INTR_VECTOR,		kvm_posted_intr_ipi),
>>   	SYSVEC(POSTED_INTR_WAKEUP_VECTOR,	kvm_posted_intr_wakeup_ipi),
>>   	SYSVEC(POSTED_INTR_NESTED_VECTOR,	kvm_posted_intr_nested_ipi),
>> +#endif
>>   };
>>   
>>   static bool fred_setup_done __initdata;
>> -- 
>> 2.39.2
> 

We want to minimize #ifdeffery (which is why we didn't add any to
sysvec_table[]), would it be better to simply remove "#if 
IS_ENABLED(CONFIG_KVM)" around the the POSTED_INTR_* macros from the
Linux-next tree?

BTW, kvm_posted_intr_*() are defined to NULL if !IS_ENABLED(CONFIG_KVM).

diff --git a/arch/x86/include/asm/irq_vectors.h 
b/arch/x86/include/asm/irq_vectors.h
index 3a19904c2db6..d18bfb238f66 100644
--- a/arch/x86/include/asm/irq_vectors.h
+++ b/arch/x86/include/asm/irq_vectors.h
@@ -84,11 +84,9 @@
  #define HYPERVISOR_CALLBACK_VECTOR	0xf3

  /* Vector for KVM to deliver posted interrupt IPI */
-#if IS_ENABLED(CONFIG_KVM)
  #define POSTED_INTR_VECTOR		0xf2
  #define POSTED_INTR_WAKEUP_VECTOR	0xf1
  #define POSTED_INTR_NESTED_VECTOR	0xf0
-#endif

  #define MANAGED_IRQ_SHUTDOWN_VECTOR	0xef