linux-kernel - Re: [PATCH v4 2/2] block-dma: properly take MMIO path

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aRTnS1NZ0yEL0pJl@kbusch-mbp>
Date: Wed, 12 Nov 2025 15:00:11 -0500
From: Keith Busch <kbusch@...nel.org>
To: Leon Romanovsky <leon@...nel.org>
Cc: Jens Axboe <axboe@...nel.dk>, Christoph Hellwig <hch@....de>,
	Sagi Grimberg <sagi@...mberg.me>, linux-block@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-nvme@...ts.infradead.org
Subject: Re: [PATCH v4 2/2] block-dma: properly take MMIO path

On Wed, Nov 12, 2025 at 09:48:05PM +0200, Leon Romanovsky wrote:
> From: Leon Romanovsky <leonro@...dia.com>
> 
> In commit eadaa8b255f3 ("dma-mapping: introduce new DMA attribute to
> indicate MMIO memory"), DMA_ATTR_MMIO attribute was added to describe
> MMIO addresses, which require to avoid any memory cache flushing, as
> an outcome of the discussion pointed in Link tag below.
> 
> In case of PCI_P2PDMA_MAP_THRU_HOST_BRIDGE transfer, blk-mq-dm logic
> treated this as regular page and relied on "struct page" DMA flow.
> That flow performs CPU cache flushing, which shouldn't be done here,
> and doesn't set IOMMU_MMIO flag in DMA-IOMMU case.
> 
> As a solution, let's encode peer-to-peer transaction type in NVMe IOD
> flags variable and provide it to blk-mq-dma API.

Looks good.

Reviewed-by: Keith Busch <kbusch@...nel.org>