Re: [PATCH 2/9] KVM: selftests: Add __packed attribute fallback

[Sean Christopherson <seanjc@google.com>]

On Fri, Aug 29, 2025, Aqib Faruqui wrote:
> Kernel UAPI headers use __packed but don't provide the definition in
> userspace builds.
> 
> Add a fallback definition matching the kernel's implementation. This
> follows the same pattern used by BPF and SGX selftests.

Ugh.  No, this needs to be fixed in a central location, not splattered all over
random subsystem selftests.  My first choice would be to copy (and keep synchronize)
all of the include/linux/compiler*.h headers to tools/include/linux/.

If for some reason that's not a viable option, we should yank the __packed and
similar #defines out of tools/include/linux/compiler-gcc.h and place them in
tools/include/linux/compiler.h.  AFAICT, none of them are actually GCC-only.

> Signed-off-by: Aqib Faruqui <aqibaf@amazon.com>
> ---
>  tools/testing/selftests/kvm/include/kvm_util.h | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
> index 23a506d7e..7fae7f5e7 100644
> --- a/tools/testing/selftests/kvm/include/kvm_util.h
> +++ b/tools/testing/selftests/kvm/include/kvm_util.h
> @@ -5,6 +5,10 @@
>  #ifndef SELFTEST_KVM_UTIL_H
>  #define SELFTEST_KVM_UTIL_H
>  
> +#ifndef __packed
> +#define __packed __attribute__((__packed__))
> +#endif
> +
>  #include "test_util.h"
>  
>  #include <linux/compiler.h>
> -- 
> 2.47.3
>