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

From: Shameerali Kolothum Thodi <[email-masked]>
Date: Thu, 6 Mar 2025 09:56:32 +0000

> -----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