linux-kernel - Re: [RFC 1/1] swiotlb: Reduce calls to swiotlb_find

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Date: Mon, 1 Jul 2024 06:36:15 +0200
From: "hch@....de" <hch@....de>
To: Michael Kelley <mhklinux@...look.com>
Cc: "hch@....de" <hch@....de>,
	Petr Tesařík <petr@...arici.cz>,
	"robin.murphy@....com" <robin.murphy@....com>,
	"joro@...tes.org" <joro@...tes.org>,
	"will@...nel.org" <will@...nel.org>,
	"jgross@...e.com" <jgross@...e.com>,
	"sstabellini@...nel.org" <sstabellini@...nel.org>,
	"oleksandr_tyshchenko@...m.com" <oleksandr_tyshchenko@...m.com>,
	"m.szyprowski@...sung.com" <m.szyprowski@...sung.com>,
	"iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>
Subject: Re: [RFC 1/1] swiotlb: Reduce calls to swiotlb_find_pool()

On Sun, Jun 30, 2024 at 02:02:52PM +0000, Michael Kelley wrote:
> 1) Rename is_swiotlb_buffer() to swiotlb_find_pool(), since it
> now returns a pool.  A NULL return value indicates that the
> paddr is not an swiotlb buffer.
> 
> 2) Similarly, rename is_xen_swiotlb_buffer() to
> xen_swiotlb_find_pool()
> 
> 3) The existing swiotlb_find_pool() has the same function signature,
> but it is used only where the paddr is known to be an swiotlb buffer
> and hence always succeeds. Rename it to __swiotlb_find_pool() as
> the "internal" version of swiotlb_find_pool().

Sounds good.

> 4) Do you still want is_swiotlb_buffer() as a trivial wrapper around
> the new swiotlb_find_pool(), for use solely in dma_direct_need_sync()
> where only a Boolean is needed and not the pool?

If there is really just a single caller left we can skip the wrapper,
otherwise it might be handy.