Re: [core-for-CI] nvme-pci: don't use dma_alloc_noncontiguous with 0 merge boundary

[Jani Nikula <jani.nikula@linux.intel.com>]

On Wed, 04 Dec 2024, Luca Coelho <luca@coelho.fi> wrote:
> Hi Chaitanya,
>
> On Wed, 2024-12-04 at 11:36 +0530, Chaitanya Kumar Borah wrote:
>> From: Christoph Hellwig <hch@lst.de>
>> 
>> Only call into nvme_alloc_host_mem_single which uses
>> dma_alloc_noncontiguous when there is non-null dma merge boundary.
>> Without this we'll call into dma_alloc_noncontiguous for device using
>> dma-direct, which can work fine as long as the preferred size is below the
>> MAX_ORDER of the page allocator, but blows up with a warning if it is
>> too large.
>> 
>> Fixes: 63a5c7a4b4c4 ("nvme-pci: use dma_alloc_noncontigous if possible")
>> Reported-by: Leon Romanovsky <leon@kernel.org>
>> Reported-by: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>
>> Signed-off-by: Christoph Hellwig <hch@lst.de>
>> References: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/13227
>> Link: https://lore.kernel.org/linux-nvme/39a67024-2926-4a20-8feb-77dd64ab7c39@kernel.dk/T/#mfef47937b20e33aa3cc63a3af930f8a9f9baf8c2
>> ---
>>  drivers/nvme/host/pci.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>> 
>> diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
>> index 4c644bb7f069..778f124c2e21 100644
>> --- a/drivers/nvme/host/pci.c
>> +++ b/drivers/nvme/host/pci.c
>> @@ -2172,6 +2172,7 @@ static int nvme_alloc_host_mem_multi(struct nvme_dev *dev, u64 preferred,
>>  
>>  static int nvme_alloc_host_mem(struct nvme_dev *dev, u64 min, u64 preferred)
>>  {
>> +	unsigned long dma_merge_moundary = dma_get_merge_boundary(dev->dev);
>>  	u64 min_chunk = min_t(u64, preferred, PAGE_SIZE * MAX_ORDER_NR_PAGES);
>>  	u64 hmminds = max_t(u32, dev->ctrl.hmminds * 4096, PAGE_SIZE * 2);
>>  	u64 chunk_size;
>> @@ -2180,7 +2181,7 @@ static int nvme_alloc_host_mem(struct nvme_dev *dev, u64 min, u64 preferred)
>>  	 * If there is an IOMMU that can merge pages, try a virtually
>>  	 * non-contiguous allocation for a single segment first.
>>  	 */
>> -	if (!(PAGE_SIZE & dma_get_merge_boundary(dev->dev))) {
>> +	if (dma_merge_moundary && (PAGE_SIZE & dma_merge_moundary) == 0) {
>>  		if (!nvme_alloc_host_mem_single(dev, preferred))
>>  			return 0;
>>  	}
>
> This looks sane and has already been reviewed in the linux-nvme mailing
> list.  So, FWIW, you have my:
>
> Acked-by: Luca Coelho <luciano.coelho@intel.com>

Pushed to core-for-CI.

BR,
Jani.

-- 
Jani Nikula, Intel