[PATCH net v2] eth: fbnic: don't build the driver when skb has more than 21 frags

[PATCH net v2] eth: fbnic: don't build the driver when skb has more than 21 frags

[Jakub Kicinski]

Similarly to commit 0e03c643dc93 ("eth: fbnic: fix s390 build."),
the driver won't build if skb_shared_info has more than 25 frags
assuming a 64B cache line and 21 frags assuming a 128B cache line.

  (512 - 48 -  64) / 16 = 25
  (512 - 48 - 128) / 16 = 21

Fixes: 0cb4c0a13723 ("eth: fbnic: Implement Rx queue alloc/start/stop/free")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
v2:
 - cover the 128B case as well
v1: https://lore.kernel.org/20240717133744.1239356-1-kuba@kernel.org
CC: alexanderduyck@fb.com
CC: kernel-team@meta.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..86034ea4ba5b 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 < 22
 	depends on PCI_MSI
 	select PHYLINK
 	help
-- 
2.45.2

Re: [PATCH net v2] eth: fbnic: don't build the driver when skb has more than 21 frags

[Paolo Abeni]

On 7/17/24 18:15, 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
> assuming a 64B cache line and 21 frags assuming a 128B cache line.
> 
>    (512 - 48 -  64) / 16 = 25
>    (512 - 48 - 128) / 16 = 21
> 
> Fixes: 0cb4c0a13723 ("eth: fbnic: Implement Rx queue alloc/start/stop/free")
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Acked-by: Paolo Abeni <pabeni@redhat.com>

Re: [PATCH net v2] eth: fbnic: don't build the driver when skb has more than 21 frags

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Paolo Abeni <pabeni@redhat.com>:

On Wed, 17 Jul 2024 09:15:59 -0700 you wrote:
> Similarly to commit 0e03c643dc93 ("eth: fbnic: fix s390 build."),
> the driver won't build if skb_shared_info has more than 25 frags
> assuming a 64B cache line and 21 frags assuming a 128B cache line.
> 
>   (512 - 48 -  64) / 16 = 25
>   (512 - 48 - 128) / 16 = 21
> 
> [...]

Here is the summary with links:
  - [net,v2] eth: fbnic: don't build the driver when skb has more than 21 frags
    https://git.kernel.org/netdev/net/c/4359836129d9

You are awesome, thank you!
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