From: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
To: Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>
Cc: thomas.lendacky-5C7GfCeVMHo@public.gmane.org,
iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org,
Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
Subject: Re: [PATCH 1/2] kernel/dma/direct: take DMA offset into account in dma_direct_supported
Date: Wed, 29 Aug 2018 18:59:56 +0200 [thread overview]
Message-ID: <20180829165956.GA6787@lst.de> (raw)
In-Reply-To: <0e95df80-38f7-7970-ef74-419567f13fdc-5wv7dgnIgG8@public.gmane.org>
On Fri, Aug 24, 2018 at 12:11:23PM +0100, Robin Murphy wrote:
> On 24/08/18 07:53, Christoph Hellwig wrote:
>> When a device has a DMA offset the dma capable result will change due
>> to the difference between the physical and DMA address. Take that into
>> account.
>
> The "phys_to_dma(..., DMA_BIT_MASK(...))" idiom always looks like a glaring
> error at first glance, but this whole function is fairly unintuitive
> anyway, and ultimately I think the change does work out to be correct.
>
> It might be nicer if we could reference max_zone_pfns[] for a bit more
> clarity, but I guess that's not arch-independent.
Not just arch specific, but also local variables. There is
arch_zone_lowest_possible_pfn in page_alloc.c, but that gets discarded
after init. That being said this is the right direction and I'll
look into it for 4.20 or later.
next prev parent reply other threads:[~2018-08-29 16:59 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-24 6:53 two dma-direct fixes for 4.18 Christoph Hellwig
[not found] ` <20180824065324.654-1-hch-jcswGhMUV9g@public.gmane.org>
2018-08-24 6:53 ` [PATCH 1/2] kernel/dma/direct: take DMA offset into account in dma_direct_supported Christoph Hellwig
[not found] ` <20180824065324.654-2-hch-jcswGhMUV9g@public.gmane.org>
2018-08-24 11:11 ` Robin Murphy
[not found] ` <0e95df80-38f7-7970-ef74-419567f13fdc-5wv7dgnIgG8@public.gmane.org>
2018-08-29 16:59 ` Christoph Hellwig [this message]
2018-08-24 6:53 ` [PATCH 2/2] kernel/dma/direct: refine dma_direct_alloc zone selection Christoph Hellwig
[not found] ` <20180824065324.654-3-hch-jcswGhMUV9g@public.gmane.org>
2018-08-24 11:38 ` Robin Murphy
[not found] ` <bfba5bae-a88c-f777-ba1f-f0db310904dc-5wv7dgnIgG8@public.gmane.org>
2018-08-24 11:49 ` Robin Murphy
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