linux-kernel - Re: [PATCH net v1] net: stmmac: TSO: Fix unbalanced DMA map/unmap for non-paged SKB data

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Message-ID: <44e7ae05-2eea-4602-b192-dbd01631169c@nvidia.com>
Date: Wed, 4 Dec 2024 17:03:14 +0000
From: Jon Hunter <jonathanh@...dia.com>
To: Furong Xu <0x1207@...il.com>, Jakub Kicinski <kuba@...nel.org>
Cc: netdev@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 Alexandre Torgue <alexandre.torgue@...s.st.com>,
 Jose Abreu <joabreu@...opsys.com>, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
 Maxime Coquelin <mcoquelin.stm32@...il.com>, xfr@...look.com,
 Suraj Jaiswal <quic_jsuraj@...cinc.com>, Thierry Reding
 <treding@...dia.com>,
 "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH net v1] net: stmmac: TSO: Fix unbalanced DMA map/unmap for
 non-paged SKB data

On 03/12/2024 03:16, Furong Xu wrote:
> On Mon, 2 Dec 2024 18:34:25 -0800, Jakub Kicinski <kuba@...nel.org> wrote:
> 
>> On Tue, 3 Dec 2024 10:03:31 +0800 Furong Xu wrote:
>>> I requested Jon to provide more info about "Tx DMA map failed" in previous
>>> reply, and he does not respond yet.
>>
>> What does it mean to provide "more info" about a print statement from
>> the driver? Is there a Kconfig which he needs to set to get more info?
>> Perhaps you should provide a debug patch he can apply on his tree, that
>> will print info about (1) which buffer mapping failed (head or frags);
>> (2) what the physical address was of the buffer that couldn't be mapped.
> 
> A debug patch to print info about buffer makes no sense here.
> Both Tegra186 Jetson TX2(tegra186-p2771-0000) and Tegra194 Jetson AGX Xavier
> (tegra194-p2972-0000) enable IOMMU/SMMU for stmmac in its device-tree node,
> buffer info should be investigated with detailed IOMMU/SMMU debug info from
> drivers/iommu/arm/arm-smmu/arm-smmu-nvidia.c together.
> 
> I am not an expert in IOMMU, so I cannot help more.
> 
> Without the help from Jon, our only choice is revert as you said.

Sorry Thierry and I were digging into this offline but yes I can provide 
any more info that is needed.

Jon

-- 
nvpublic