netdev - Re: [PATCH net] eth: fbnic: don't build the driver when skb has more than 25 frags

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Message-ID: <43bc03f0-5e5a-4265-898b-8ca526d6cc75@redhat.com>
Date: Wed, 17 Jul 2024 15:44:09 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Jakub Kicinski <kuba@...nel.org>, davem@...emloft.net
Cc: netdev@...r.kernel.org, edumazet@...gle.com, alexanderduyck@...com,
 kernel-team@...a.com
Subject: Re: [PATCH net] eth: fbnic: don't build the driver when skb has more
 than 25 frags



On 7/17/24 15:37, Jakub Kicinski wrote:
> Similarly to commit 0e03c643dc93 ("eth: fbnic: fix s390 build."),
> the driver won't build if skb_shared_info has more than 25 frags.
> 
> Fixes: 0cb4c0a13723 ("eth: fbnic: Implement Rx queue alloc/start/stop/free")
> Signed-off-by: Jakub Kicinski <kuba@...nel.org>
> ---
> CC: alexanderduyck@...com
> CC: kernel-team@...a.com
> ---
>   drivers/net/ethernet/meta/Kconfig | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/net/ethernet/meta/Kconfig b/drivers/net/ethernet/meta/Kconfig
> index a9f078212c78..b599c71a2d27 100644
> --- a/drivers/net/ethernet/meta/Kconfig
> +++ b/drivers/net/ethernet/meta/Kconfig
> @@ -21,6 +21,7 @@ config FBNIC
>   	tristate "Meta Platforms Host Network Interface"
>   	depends on X86_64 || COMPILE_TEST
>   	depends on S390=n
> +	depends on MAX_SKB_FRAGS < 26

I think that with aarch MAX_SKB_FRAGS should be max 21. Aarch cacheline 
size is 128, right? The frag independent part of skb_shared_info takes 
48 bytes, and sizeof(skb_frag_t) == 16:

(512 - 128 - 48)/16 = 21

Cheers,

Paolo