Re: [PATCH] KVM: fix kvm_mmu_memory_cache allocation warning

Marc Zyngier
2024-02-12T11:51:46Z

On Mon, 12 Feb 2024 11:24:10 +0000,
Arnd Bergmann <arnd@kernel.org> wrote:
>
> From: Arnd Bergmann <arnd@arndb.de>
>
> gcc-14 notices that the arguments to kvmalloc_array() are mixed up:
>
> arch/x86/kvm/../../../virt/kvm/kvm_main.c: In function '__kvm_mmu_topup_memory_cache':
> arch/x86/kvm/../../../virt/kvm/kvm_main.c:424:53: error: 'kvmalloc_array' sizes specified with 'sizeof' in the earlier argument and not in the later argument [-Werror=calloc-transposed-args]
> 424 | mc->objects = kvmalloc_array(sizeof(void *), capacity, gfp);
> | ^~~~
> arch/x86/kvm/../../../virt/kvm/kvm_main.c:424:53: note: earlier argument should specify number of elements, later size of each element
>
> The code still works correctly, but the incorrect order prevents the compiler
> from properly tracking the object sizes.
>
> Fixes: 837f66c71207 ("KVM: Allow for different capacities in kvm_mmu_memory_cache structs")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> virt/kvm/kvm_main.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 8f03b56dafbd..4c48f61cae35 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -421,7 +421,7 @@ int __kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int capacity,
> if (WARN_ON_ONCE(!capacity))
> return -EIO;
>
> - mc->objects = kvmalloc_array(sizeof(void *), capacity, gfp);
> + mc->objects = kvmalloc_array(capacity, sizeof(void *), gfp);
> if (!mc->objects)
> return -ENOMEM;
>

Huh, well spotted GCC. And thanks Arnd for the fix.

Reviewed-by: Marc Zyngier <maz@kernel.org>

M.

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