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Date: Thu, 28 Aug 2025 09:19:20 -0600
From: Keith Busch <kbusch@kernel.org>
To: Leon Romanovsky <leon@kernel.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>,
	Leon Romanovsky <leonro@nvidia.com>,
	Jason Gunthorpe <jgg@nvidia.com>,
	Abdiel Janulgue <abdiel.janulgue@gmail.com>,
	Alexander Potapenko <glider@google.com>,
	Alex Gaynor <alex.gaynor@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Christoph Hellwig <hch@lst.de>, Danilo Krummrich <dakr@kernel.org>,
	iommu@lists.linux.dev, Jason Wang <jasowang@redhat.com>,
	Jens Axboe <axboe@kernel.dk>, Joerg Roedel <joro@8bytes.org>,
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	kasan-dev@googlegroups.com, linux-block@vger.kernel.org,
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	Madhavan Srinivasan <maddy@linux.ibm.com>,
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	xen-devel@lists.xenproject.org
Subject: Re: [PATCH v4 15/16] block-dma: properly take MMIO path
Message-ID: <aLBzeMNT3WOrjprC@kbusch-mbp>
References: <cover.1755624249.git.leon@kernel.org>
 <642dbeb7aa94257eaea71ec63c06e3f939270023.1755624249.git.leon@kernel.org>
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In-Reply-To: <642dbeb7aa94257eaea71ec63c06e3f939270023.1755624249.git.leon@kernel.org>

On Tue, Aug 19, 2025 at 08:36:59PM +0300, Leon Romanovsky wrote:
> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> index 09b99d52fd36..283058bcb5b1 100644
> --- a/include/linux/blk_types.h
> +++ b/include/linux/blk_types.h
> @@ -387,6 +387,7 @@ enum req_flag_bits {
>  	__REQ_FS_PRIVATE,	/* for file system (submitter) use */
>  	__REQ_ATOMIC,		/* for atomic write operations */
>  	__REQ_P2PDMA,		/* contains P2P DMA pages */
> +	__REQ_MMIO,		/* contains MMIO memory */
>  	/*
>  	 * Command specific flags, keep last:
>  	 */
> @@ -420,6 +421,7 @@ enum req_flag_bits {
>  #define REQ_FS_PRIVATE	(__force blk_opf_t)(1ULL << __REQ_FS_PRIVATE)
>  #define REQ_ATOMIC	(__force blk_opf_t)(1ULL << __REQ_ATOMIC)
>  #define REQ_P2PDMA	(__force blk_opf_t)(1ULL << __REQ_P2PDMA)
> +#define REQ_MMIO	(__force blk_opf_t)(1ULL << __REQ_MMIO)

Now that my integrity metadata DMA series is staged, I don't think we
can use REQ flags like this because data and metadata may have different
mapping types. I think we should add a flags field to the dma_iova_state
instead.