linux-kernel - Re: [PATCH net-next v10 4/4] page_pool: skip dma sync operation for inflight pages

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 for Android: free password hash cracker in your pocket

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

Message-ID: <20250305172906.GG5011@ziepe.ca>
Date: Wed, 5 Mar 2025 13:29:06 -0400
From: Jason Gunthorpe <jgg@...pe.ca>
To: Yunsheng Lin <linyunsheng@...wei.com>
Cc: davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
	zhangkun09@...wei.com, liuyonglong@...wei.com,
	fanghaiqing@...wei.com, Robin Murphy <robin.murphy@....com>,
	Alexander Duyck <alexander.duyck@...il.com>,
	IOMMU <iommu@...ts.linux.dev>,
	Jesper Dangaard Brouer <hawk@...nel.org>,
	Ilias Apalodimas <ilias.apalodimas@...aro.org>,
	Eric Dumazet <edumazet@...gle.com>, Simon Horman <horms@...nel.org>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v10 4/4] page_pool: skip dma sync operation for
 inflight pages

On Wed, Feb 26, 2025 at 07:03:39PM +0800, Yunsheng Lin wrote:
> Skip dma sync operation for inflight pages before the
> sync operation in page_pool_item_unmap() as DMA API
> expects to be called with a valid device bound to a
> driver as mentioned in [1].
> 
> After page_pool_destroy() is called, the page is not
> expected to be recycled back to pool->alloc cache and
> dma sync operation is not needed when the page is not
> recyclable or pool->ring is full, so only skip the dma
> sync operation for the infilght pages by clearing the
> pool->dma_sync, as rcu sync operation in
> page_pool_destroy() is paired with rcu lock in
> page_pool_recycle_in_ring() to ensure that there is no
> dma sync operation called after rcu sync operation.

Are you guaranteeing that the cache is made consistent before freeing
the page back to the mm? That is required..

Jason