Subject: Re: linux-next: build failure after merge of the kvm-arm tree

From: Marc Zyngier <[email-masked]>
Date: Fri, 07 Mar 2025 00:00:15 +0000

On Thu, 06 Mar 2025 09:56:32 +0000,
Shameerali Kolothum Thodi <[email-masked]> wrote:
> 
> 
> 
> > -----Original Message-----
> > From: Stephen Rothwell <[email-masked]>
> > Sent: Thursday, March 6, 2025 5:46 AM
> > To: Christoffer Dall <[email-masked]>; Marc Zyngier
> > <[email-masked]>
> > Cc: Oliver Upton <[email-masked]>; Shameerali Kolothum Thodi
> > <[email-masked]>; Linux Kernel Mailing List
> > <[email-masked]>; Linux Next Mailing List <linux-
> > [email-masked]>
> > Subject: linux-next: build failure after merge of the kvm-arm tree
> > 
> > Hi all,
> > 
> > After merging the kvm-arm tree, today's linux-next build (arm
> > multi_v7_defconfig) failed like this:
> > 
> > drivers/firmware/smccc/kvm_guest.c:58:14: warning: no previous prototype
> > for 'kvm_arm_target_impl_cpu_init' [-Wmissing-prototypes]
> >    58 | void  __init kvm_arm_target_impl_cpu_init(void)
> >       |              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > drivers/firmware/smccc/kvm_guest.c: In function
> > 'kvm_arm_target_impl_cpu_init':
> > drivers/firmware/smccc/kvm_guest.c:89:39: error: invalid application of
> > 'sizeof' to incomplete type 'struct target_impl_cpu'
> >    89 |         target = memblock_alloc(sizeof(*target) * max_cpus,
> > __alignof__(*target));
> >       |                                       ^
> > drivers/firmware/smccc/kvm_guest.c:89:62: error: invalid application of
> > '__alignof__' to incomplete type 'struct target_impl_cpu'
> >    89 |         target = memblock_alloc(sizeof(*target) * max_cpus,
> > __alignof__(*target));
> >       |                                                              ^~~~~~~~~~~
> > drivers/firmware/smccc/kvm_guest.c:102:23: error: invalid use of undefined
> > type 'struct target_impl_cpu'
> >   102 |                 target[i].midr = res.a1;
> >       |                       ^
> > drivers/firmware/smccc/kvm_guest.c:102:26: error: invalid use of undefined
> > type 'struct target_impl_cpu'
> >   102 |                 target[i].midr = res.a1;
> >       |                          ^
> > drivers/firmware/smccc/kvm_guest.c:103:23: error: invalid use of undefined
> > type 'struct target_impl_cpu'
> >   103 |                 target[i].revidr = res.a2;
> >       |                       ^
> > drivers/firmware/smccc/kvm_guest.c:103:26: error: invalid use of undefined
> > type 'struct target_impl_cpu'
> >   103 |                 target[i].revidr = res.a2;
> >       |                          ^
> > drivers/firmware/smccc/kvm_guest.c:104:23: error: invalid use of undefined
> > type 'struct target_impl_cpu'
> >   104 |                 target[i].aidr = res.a3;
> >       |                       ^
> > drivers/firmware/smccc/kvm_guest.c:104:26: error: invalid use of undefined
> > type 'struct target_impl_cpu'
> >   104 |                 target[i].aidr = res.a3;
> >       |                          ^
> > drivers/firmware/smccc/kvm_guest.c:107:14: error: implicit declaration of
> > function 'cpu_errata_set_target_impl' [-Wimplicit-function-declaration]
> >   107 |         if (!cpu_errata_set_target_impl(max_cpus, target)) {
> >       |              ^~~~~~~~~~~~~~~~~~~~~~~~~~
> > drivers/firmware/smccc/kvm_guest.c:116:37: error: invalid application of
> > 'sizeof' to incomplete type 'struct target_impl_cpu'
> >   116 |         memblock_free(target, sizeof(*target) * max_cpus);
> >       |                                     ^
> > 
> > Caused by commit
> > 
> >   86edf6bdcf05 ("smccc/kvm_guest: Enable errata based on implementation
> > CPUs")
> > 
> > I have used the kvm-arm tree from next-20250305 for today.
> 
> Thanks for reporting this.
> 
> Hmm..kvm_guest.c gets build through HAVE_ARM_SMCCC_DISCOVERY 
> which is selected by ARM_GIC_V3.
> 
> We could limit the kvm_arm_target_impl_cpu_init() to ARM64 to fix this
> like below as these hypercall is only supported for KVM/ARM64.
> 
> Or is there a better way to handle this?
> 
> Thanks,
> Shameer
> 
> ---8---
> diff --git a/drivers/firmware/smccc/kvm_guest.c
> b/drivers/firmware/smccc/kvm_guest.c
> index 2f03b582c298..5767aed25cdc 100644
> --- a/drivers/firmware/smccc/kvm_guest.c
> +++ b/drivers/firmware/smccc/kvm_guest.c
> @@ -55,6 +55,7 @@ bool kvm_arm_hyp_service_available(u32 func_id)
>  }
>  EXPORT_SYMBOL_GPL(kvm_arm_hyp_service_available);
> 
> +#ifdef CONFIG_ARM64
>  void  __init kvm_arm_target_impl_cpu_init(void)
>  {
>         int i;
> @@ -115,3 +116,4 @@ void  __init kvm_arm_target_impl_cpu_init(void)
>  mem_free:
>         memblock_free(target, sizeof(*target) * max_cpus);
>  }
> +#endif

Yeah, that's probably best for now.

Oliver, do you mind stashing this on top so that -next can build
again? We can revisit this and have a better solution down the line.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.