linux-kernel - Re: [PATCH net-next v4 6/8] gve: Add rx hardware timestamp expansion

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Message-ID: <5857c5e4-ebdd-49ee-b4c5-05df1a27e6ce@linux.dev>
Date: Tue, 10 Jun 2025 10:49:06 +0100
From: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
To: Harshitha Ramamurthy <hramamurthy@...gle.com>, netdev@...r.kernel.org
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
 pabeni@...hat.com, jeroendb@...gle.com, andrew+netdev@...n.ch,
 willemb@...gle.com, ziweixiao@...gle.com, pkaligineedi@...gle.com,
 yyd@...gle.com, joshwash@...gle.com, shailend@...gle.com, linux@...blig.org,
 thostet@...gle.com, jfraker@...gle.com, richardcochran@...il.com,
 jdamato@...tly.com, horms@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v4 6/8] gve: Add rx hardware timestamp expansion

On 09/06/2025 19:40, Harshitha Ramamurthy wrote:
> From: John Fraker <jfraker@...gle.com>
> 
> Allow the rx path to recover the high 32 bits of the full 64 bit rx
> timestamp.
> 
> Use the low 32 bits of the last synced nic time and the 32 bits of the
> timestamp provided in the rx descriptor to generate a difference, which
> is then applied to the last synced nic time to reconstruct the complete
> 64-bit timestamp.
> 
> This scheme remains accurate as long as no more than ~2 seconds have
> passed between the last read of the nic clock and the timestamping
> application of the received packet.
> 
> Signed-off-by: John Fraker <jfraker@...gle.com>
> Signed-off-by: Ziwei Xiao <ziweixiao@...gle.com>
> Reviewed-by: Willem de Bruijn <willemb@...gle.com>
> Signed-off-by: Harshitha Ramamurthy <hramamurthy@...gle.com>
> ---
>   Changes in v3:
>   - Change the last_read to be u64 (Vadim Fedorenko)
> 
>   Changes in v2:
>   - Add the missing READ_ONCE (Joe Damato)
> ---

Reviewed-by: Vadim Fedorenko <vadim.fedorenko@...ux.dev>