linux-kernel - Re: [PATCH v1 07/16] dma-mapping: convert dma_direct_*map_page to be phys_addr

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Message-ID: <20250807121327.GG184255@nvidia.com>
Date: Thu, 7 Aug 2025 09:13:27 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Leon Romanovsky <leon@...nel.org>
Cc: Marek Szyprowski <m.szyprowski@...sung.com>,
	Leon Romanovsky <leonro@...dia.com>,
	Abdiel Janulgue <abdiel.janulgue@...il.com>,
	Alexander Potapenko <glider@...gle.com>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Hellwig <hch@....de>, Danilo Krummrich <dakr@...nel.org>,
	iommu@...ts.linux.dev, Jason Wang <jasowang@...hat.com>,
	Jens Axboe <axboe@...nel.dk>, Joerg Roedel <joro@...tes.org>,
	Jonathan Corbet <corbet@....net>, Juergen Gross <jgross@...e.com>,
	kasan-dev@...glegroups.com, Keith Busch <kbusch@...nel.org>,
	linux-block@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-nvme@...ts.infradead.org, linuxppc-dev@...ts.ozlabs.org,
	linux-trace-kernel@...r.kernel.org,
	Madhavan Srinivasan <maddy@...ux.ibm.com>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Miguel Ojeda <ojeda@...nel.org>,
	Robin Murphy <robin.murphy@....com>, rust-for-linux@...r.kernel.org,
	Sagi Grimberg <sagi@...mberg.me>,
	Stefano Stabellini <sstabellini@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	virtualization@...ts.linux.dev, Will Deacon <will@...nel.org>,
	xen-devel@...ts.xenproject.org
Subject: Re: [PATCH v1 07/16] dma-mapping: convert dma_direct_*map_page to be
 phys_addr_t based

On Mon, Aug 04, 2025 at 03:42:41PM +0300, Leon Romanovsky wrote:
> --- a/kernel/dma/direct.h
> +++ b/kernel/dma/direct.h
> @@ -80,42 +80,54 @@ static inline void dma_direct_sync_single_for_cpu(struct device *dev,
>  		arch_dma_mark_clean(paddr, size);
>  }
>  
> -static inline dma_addr_t dma_direct_map_page(struct device *dev,
> -		struct page *page, unsigned long offset, size_t size,
> -		enum dma_data_direction dir, unsigned long attrs)
> +static inline dma_addr_t dma_direct_map_phys(struct device *dev,
> +		phys_addr_t phys, size_t size, enum dma_data_direction dir,
> +		unsigned long attrs)
>  {
> -	phys_addr_t phys = page_to_phys(page) + offset;
> -	dma_addr_t dma_addr = phys_to_dma(dev, phys);
> +	bool is_mmio = attrs & DMA_ATTR_MMIO;
> +	dma_addr_t dma_addr;
> +	bool capable;
> +
> +	dma_addr = (is_mmio) ? phys : phys_to_dma(dev, phys);
> +	capable = dma_capable(dev, dma_addr, size, is_mmio);
> +	if (is_mmio) {
> +	       if (unlikely(!capable))
> +		       goto err_overflow;
> +	       return dma_addr;

Similar remark here, shouldn't we be checking swiotlb things for
ATTR_MMIO and failing if swiotlb is needed?

> -	if (is_swiotlb_force_bounce(dev)) {
> -		if (is_pci_p2pdma_page(page))
> -			return DMA_MAPPING_ERROR;

This

> -	if (unlikely(!dma_capable(dev, dma_addr, size, true)) ||
> -	    dma_kmalloc_needs_bounce(dev, size, dir)) {
> -		if (is_pci_p2pdma_page(page))
> -			return DMA_MAPPING_ERROR;

And this

Jason