linux-kernel - Re: [PATCH v3 5/7] x86/dma/amd-gart: Stop resizing dma_debug

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Date:   Mon, 10 Dec 2018 22:26:30 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Robin Murphy <robin.murphy@....com>
cc:     hch@....de, m.szyprowski@...sung.com,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        cai@....us, salil.mehta@...wei.com, john.garry@...wei.com,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org
Subject: Re: [PATCH v3 5/7] x86/dma/amd-gart: Stop resizing dma_debug_entry
 pool

On Mon, 10 Dec 2018, Robin Murphy wrote:

> dma-debug is now capable of adding new entries to its pool on-demand if
> the initial preallocation was insufficient, so the IOMMU_LEAK logic no
> longer needs to explicitly change the pool size. This does lose it the
> ability to save a couple of megabytes of RAM by reducing the pool size
> below its default, but it seems unlikely that that is a realistic
> concern these days (or indeed that anyone is actively debugging AGP
> drivers' DMA usage any more). Getting rid of dma_debug_resize_entries()
> will make room for further streamlining in the dma-debug code itself.
> 
> Removing the call reveals quite a lot of cruft which has been useless
> for nearly a decade since commit 19c1a6f5764d ("x86 gart: reimplement
> IOMMU_LEAK feature by using DMA_API_DEBUG"), including the entire
> 'iommu=leak' parameter, which controlled nothing except whether
> dma_debug_resize_entries() was called or not.
> 
> CC: Thomas Gleixner <tglx@...utronix.de>
> CC: Ingo Molnar <mingo@...hat.com>
> CC: Borislav Petkov <bp@...en8.de>
> CC: "H. Peter Anvin" <hpa@...or.com>
> CC: x86@...nel.org
> Reviewed-by: Christoph Hellwig <hch@....de>
> Signed-off-by: Robin Murphy <robin.murphy@....com>

Acked-by: Thomas Gleixner <tglx@...utronix.de>