linux-kernel - Re: [PATCH 6/9] dma-remap: support DMA_ATTR_NO_KERNEL

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Message-ID: <20181201170506.GE20912@lst.de>
Date:   Sat, 1 Dec 2018 18:05:06 +0100
From:   Christoph Hellwig <hch@....de>
To:     Robin Murphy <robin.murphy@....com>
Cc:     Christoph Hellwig <hch@....de>, iommu@...ts.linux-foundation.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>, Guo Ren <ren_guo@...ky.com>,
        Laura Abbott <labbott@...hat.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/9] dma-remap: support DMA_ATTR_NO_KERNEL_MAPPING

On Fri, Nov 30, 2018 at 07:05:40PM +0000, Robin Murphy wrote:
> On 05/11/2018 12:19, Christoph Hellwig wrote:
>> Do not waste vmalloc space on allocations that do not require a mapping
>> into the kernel address space.
>>
>> Signed-off-by: Christoph Hellwig <hch@....de>
>> ---
>>   kernel/dma/remap.c | 11 +++++++++--
>>   1 file changed, 9 insertions(+), 2 deletions(-)
>>
>> diff --git a/kernel/dma/remap.c b/kernel/dma/remap.c
>> index 8f1fca34b894..10a545126b0b 100644
>> --- a/kernel/dma/remap.c
>> +++ b/kernel/dma/remap.c
>> @@ -200,7 +200,8 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
>>     	size = PAGE_ALIGN(size);
>>   -	if (!gfpflags_allow_blocking(flags)) {
>> +	if (!gfpflags_allow_blocking(flags) &&
>> +	    !(attrs & DMA_ATTR_NO_KERNEL_MAPPING)) {
>>   		ret = dma_alloc_from_pool(size, &page, flags);
>>   		if (!ret)
>>   			return NULL;
>> @@ -215,6 +216,9 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
>>   	/* remove any dirty cache lines on the kernel alias */
>>   	arch_dma_prep_coherent(page, size);
>>   +	if (attrs & DMA_ATTR_NO_KERNEL_MAPPING)
>> +		return page; /* opaqueue cookie */
>
> Best to preempt the inevitable patch fixing that typo in 3 months' time. 
> Otherwise,

Thanks,

fixed.