From: Alexey Kardashevskiy <aik@ozlabs.ru>
To: Christoph Hellwig <hch@lst.de>
Cc: Michael Ellerman <mpe@ellerman.id.au>,
iommu@lists.linux-foundation.org, linuxppc-dev@lists.ozlabs.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH kernel v2 1/2] dma: Allow mixing bypass and normal IOMMU operation
Date: Thu, 29 Oct 2020 10:11:45 +1100 [thread overview]
Message-ID: <f4420b19-05cd-5817-9ba4-8f6f166a7e5c@ozlabs.ru> (raw)
In-Reply-To: <20201028172106.GA10015@lst.de>
On 29/10/2020 04:21, Christoph Hellwig wrote:
> On Wed, Oct 28, 2020 at 05:55:23PM +1100, Alexey Kardashevskiy wrote:
>>
>> It is passing an address of the end of the mapped area so passing a page
>> struct means passing page and offset which is an extra parameter and we do
>> not want to do anything with the page in those hooks anyway so I'd keep it
>> as is.
>>
>>
>>> and
>>> maybe even hide the dma_map_direct inside it.
>>
>> Call dma_map_direct() from arch_dma_map_page_direct() if
>> arch_dma_map_page_direct() is defined? Seems suboptimal as it is going to
>> be bypass=true in most cases and we save one call by avoiding calling
>> arch_dma_map_page_direct(). Unless I missed something?
>
> C does not even evaluate the right hand side of a || expression if the
> left hand evaluates to true.
Right, this is what I meant. dma_map_direct() is inline and fast so I
did not want it inside the arch hook which is not inline.
--
Alexey
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next prev parent reply other threads:[~2020-10-28 23:19 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-27 10:18 [PATCH kernel v2 0/2] DMA, powerpc/dma: Fallback to dma_ops when persistent memory present Alexey Kardashevskiy
2020-10-27 10:18 ` [PATCH kernel v2 1/2] dma: Allow mixing bypass and normal IOMMU operation Alexey Kardashevskiy
2020-10-27 16:48 ` Christoph Hellwig
2020-10-28 6:55 ` Alexey Kardashevskiy
2020-10-28 17:21 ` Christoph Hellwig
2020-10-28 23:11 ` Alexey Kardashevskiy [this message]
2020-10-27 10:18 ` [PATCH kernel v2 2/2] powerpc/dma: Fallback to dma_ops when persistent memory present Alexey Kardashevskiy
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