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

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Date: Sun, 30 Jun 2024 14:02:52 +0000
From: Michael Kelley <mhklinux@...look.com>
To: "hch@....de" <hch@....de>
CC: 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()

From: hch@....de <hch@....de> Sent: Saturday, June 29, 2024 10:56 PM
> 
> On Sat, Jun 29, 2024 at 03:55:58PM +0000, Michael Kelley wrote:
> > Unless there is further discussion on this point, I'll just keep the original
> > "is_swiotlb_buffer()" in v2.
> 
> That is the wrong name for something that returns the pool as pointed
> out before.

OK. Since any new name could cause confusion with the existing
swiotlb_find_pool(), here's my proposal:

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().

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?

Thanks,

Michael