Re: [RFC PATCH Dovetail 7.1] x86: irq_pipeline: Allow X86_FRED to be enabled

On Mon, 2026-06-01 at 19:58 +0200, Florian Bezdeka wrote:
> Some low level entry functions, fred_##func were not defined when
> FRED has been enabled:
> 
> ld: vmlinux.o:(.data..ro_after_init+0x6100): undefined reference to `fred_sysvec_apic_timer_interrupt'
> ld: vmlinux.o:(.data..ro_after_init+0x6120): undefined reference to `fred_sysvec_kvm_posted_intr_nested_ipi'
> ld: vmlinux.o:(.data..ro_after_init+0x6128): undefined reference to `fred_sysvec_kvm_posted_intr_wakeup_ipi'
> ld: vmlinux.o:(.data..ro_after_init+0x6130): undefined reference to `fred_sysvec_kvm_posted_intr_ipi'
> ld: vmlinux.o:(.data..ro_after_init+0x6150): undefined reference to `fred_sysvec_irq_work'
> ld: vmlinux.o:(.data..ro_after_init+0x6158): undefined reference to `fred_sysvec_x86_platform_ipi'
> ld: vmlinux.o:(.data..ro_after_init+0x6160): undefined reference to `fred_sysvec_reboot'
> ld: vmlinux.o:(.data..ro_after_init+0x6178): undefined reference to `fred_sysvec_call_function_single'
> ld: vmlinux.o:(.data..ro_after_init+0x6180): undefined reference to `fred_sysvec_call_function'
> ld: vmlinux.o:(.data..ro_after_init+0x6188): undefined reference to `fred_sysvec_reschedule_ipi'
> ld: vmlinux.o:(.data..ro_after_init+0x6198): undefined reference to `fred_sysvec_spurious_apic_interrupt'
> 
> Updating the DEFINE_IDTENTRY_SYSVEC_PIPELINED() and
> DEFINE_IDTENTRY_SYSVEC_PIPELINED_NORETURN() macros to define those
> functions.
> 
> FRED entry points for sysvecs will no go through the IRQ pipeline as
> we do it for the IDT.
> 
> Signed-off-by: Florian Bezdeka <[email protected]>
> ---
> 
> Hi Philippe,
> 
> input highly welcome. This allows to build x86 with FRED enabled, which
> fixes a compile time issue introduced with 7.1-rc5.
> 
> On first glance that seems to do the right thing, but as always I might
> miss something.

Forgot to mention: The most important file to review is most likely
arch/x86/entry/entry_fred.c.

> 
>  arch/x86/Kconfig                |  2 +-
>  arch/x86/include/asm/idtentry.h | 11 +++++++++++
>  2 files changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 4d40fbb58b1c..fc6500301ff9 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -554,7 +554,7 @@ config X86_CPU_RESCTRL_INTEL_AET
>  
>  config X86_FRED
>  	bool "Flexible Return and Event Delivery"
> -	depends on X86_64 && !IRQ_PIPELINE
> +	depends on X86_64
>  	help
>  	  When enabled, use Flexible Return and Event Delivery
>  	  instead of the legacy SYSCALL/SYSENTER/IDT architecture for
> diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
> index 0b517059ae9d..bb1df662dc56 100644
> --- a/arch/x86/include/asm/idtentry.h
> +++ b/arch/x86/include/asm/idtentry.h
> @@ -222,6 +222,11 @@ static __always_inline void __##func(struct pt_regs *regs, u8 vector)
>   */
>  #define DEFINE_IDTENTRY_SYSVEC_PIPELINED(vector, func)			\
>  __visible noinstr void func(struct pt_regs *regs)			\
> +{									\
> +	arch_pipeline_entry(regs, vector);				\
> +}									\
> +									\
> +void fred_##func(struct pt_regs *regs)					\
>  {									\
>  	arch_pipeline_entry(regs, vector);				\
>  }									\
> @@ -233,6 +238,12 @@ __visible noinstr void func(struct pt_regs *regs)			\
>  {									\
>  	arch_pipeline_entry(regs, vector);				\
>  }									\
> +									\
> +void fred_##func(struct pt_regs *regs)					\
> +{									\
> +	arch_pipeline_entry(regs, vector);				\
> +}									\
> +									\
>  __visible __noreturn void __##func(struct pt_regs *regs)
>  
>  #define DEFINE_IDTENTRY_SYSVEC_SIMPLE_PIPELINED(vector, func)		\