linux-kernel - Re: [PATCH] usbip: Fix the error limitation on max_hw

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Message-ID: <c49917d2-5157-4878-9866-be6053b5124d@linuxfoundation.org>
Date: Tue, 4 Mar 2025 12:45:28 -0700
From: Shuah Khan <skhan@...uxfoundation.org>
To: Zongmin Zhou <min_halo@....com>
Cc: valentina.manea.m@...il.com, shuah@...nel.org, i@...ithal.me,
 gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
 linux-kernel@...r.kernel.org, Zongmin Zhou <zhouzongmin@...inos.cn>,
 Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH] usbip: Fix the error limitation on max_hw_sectors for
 usbip device

On 3/2/25 05:37, Zongmin Zhou wrote:
> Dear shuah,
> 
> 
> Yes, I agree with you.It would be better if there have a more simpler fixes than This patch.
> 
> I can just think of the two possible solutions that mentioned before.

What are the two possible solutions?
> 
> 
> If SWIOTLB disabled,dma_max_mapping_size() return SIZE_MAX.

Right when CONFIG_HAS_DMA, if not it returns 0. Perhaps we
can ignore CONFIG_HAS_DMA=n for this for this discussion.

> 
> Only if SWIOTLB is active and dma addressing limited will return the swiotlb max mapping size.
> 
> 
> The swiotlb config seems rely on many other config options like x86_64/IOMMU_SUPPORT and so on,
> 
> and the configuration on host and client side only use the default at all,Like the default ubuntu release version.
> 
> It seems that switlb is enabled by default on most platforms.

If understand correctly the problem happens only when SWIOTLB
is enabled on client or host?

The following combinations are possible:

SWILTLB enabled on client and disabled on host - rate limited?
SWILTLB enabled on client and enabled on host - rate limited?
SWILTLB disabled on client and enabled on host - rate limited?
SWILTLB disabled on client and disabled on host - not a problem

thanks,
-- Shuah