linux-kernel - Re: [PATCH v2 2/2] dma: add IOMMU static calls with clear default ops

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Message-ID: <20240729171518.GB31388@lst.de>
Date: Mon, 29 Jul 2024 19:15:18 +0200
From: Christoph Hellwig <hch@....de>
To: Mostafa Saleh <smostafa@...gle.com>
Cc: Leon Romanovsky <leon@...nel.org>, Christoph Hellwig <hch@....de>,
	Robin Murphy <robin.murphy@....com>, Joerg Roedel <joro@...tes.org>,
	Will Deacon <will@...nel.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Leon Romanovsky <leonro@...dia.com>,
	Easwar Hariharan <eahariha@...ux.microsoft.com>,
	linux-kernel@...r.kernel.org, iommu@...ts.linux.dev,
	Jason Gunthorpe <jgg@...dia.com>
Subject: Re: [PATCH v2 2/2] dma: add IOMMU static calls with clear default
 ops

On Mon, Jul 29, 2024 at 12:41:12PM +0000, Mostafa Saleh wrote:
> Just out of curiosity, is there any observed improvement from that?
> As from my experience the DMA-IOMMU path is quite dense so it won't
> be senstive to such micro-optimizations.

We are trying to gradually fix this.   Part of that is adding not even
more indirect calls for the next generation map API.  But another totally
unrelated part is that we can compile out the dma ops entirely for
common configs, which I really want because people are badly abusing it.