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

[Xin Li]

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@xxxxxxxxx>
> > ---
> >   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