Re: [PATCH 6/9] dma-remap: support DMA_ATTR_NO_KERNEL_MAPPING

From: Christoph Hellwig <hch@lst.de>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Christoph Hellwig <hch@lst.de>,
	iommu@lists.linux-foundation.org,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>, Guo Ren <ren_guo@c-sky.com>,
	Laura Abbott <labbott@redhat.com>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 6/9] dma-remap: support DMA_ATTR_NO_KERNEL_MAPPING
Date: Sat, 1 Dec 2018 18:05:06 +0100	[thread overview]
Message-ID: <20181201170506.GE20912@lst.de> (raw)
In-Reply-To: <e993440c-53bf-8071-b1b6-06d022d39e4e@arm.com>

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@lst.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.