linux-kernel - Re: [PATCH bpf-next 1/4] bpf: tailcall: Introduce bpf_arch_tail_call_prologue

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Message-Id: <45f1e1978b7dc28e522dcc0a72954d892b37a85220749bd027c7395edb01d991@mail.kernel.org>
Date: Fri,  2 Jan 2026 15:21:09 +0000 (UTC)
From: bot+bpf-ci@...nel.org
To: leon.hwang@...ux.dev,bpf@...r.kernel.org
Cc: ast@...nel.org,daniel@...earbox.net,andrii@...nel.org,martin.lau@...ux.dev,eddyz87@...il.com,song@...nel.org,yonghong.song@...ux.dev,john.fastabend@...il.com,kpsingh@...nel.org,sdf@...ichev.me,haoluo@...gle.com,jolsa@...nel.org,puranjay@...nel.org,xukuohai@...weicloud.com,catalin.marinas@....com,will@...nel.org,davem@...emloft.net,dsahern@...nel.org,tglx@...utronix.de,mingo@...hat.com,bp@...en8.de,dave.hansen@...ux.intel.com,x86@...nel.org,hpa@...or.com,akpm@...ux-foundation.org,linux-arm-kernel@...ts.infradead.org,linux-kernel@...r.kernel.org,netdev@...r.kernel.org,kernel-patches-bot@...com,leon.hwang@...ux.dev,ast@...nel.org,andrii@...nel.org,daniel@...earbox.net,martin.lau@...nel.org,eddyz87@...il.com,yonghong.song@...ux.dev,clm@...a.com,ihor.solodrai@...ux.dev
Subject: Re: [PATCH bpf-next 1/4] bpf: tailcall: Introduce bpf_arch_tail_call_prologue_offset

> diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
> index 1eeb31c5b317..beedd1281c22 100644
> --- a/kernel/bpf/arraymap.c
> +++ b/kernel/bpf/arraymap.c
> @@ -127,6 +127,9 @@ static struct bpf_map *array_map_alloc(union bpf_attr *attr)
>  			array_size += (u64) max_entries * elem_size;
>  		}
>  	}
> +	if (attr->map_type == BPF_MAP_TYPE_PROG_ARRAY && bpf_arch_tail_call_prologue_offset())
> +		/* Store tailcall targets */
> +		array_size += (u64) max_entries * sizeof(void *);

Should array_map_mem_usage() also account for this additional space?
Currently array_map_mem_usage() handles special cases for percpu arrays
and mmapable arrays, but has no corresponding check for PROG_ARRAY maps
when bpf_arch_tail_call_prologue_offset() is non-zero. This would cause
the reported memory usage to be lower than the actual allocation when
an architecture implements this function (e.g., x86_64 and arm64 in the
subsequent patches of this series).

[ ... ]


---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/20660615603