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  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]
Date:   Mon, 28 Mar 2022 08:37:23 +0200
From:   Christoph Hellwig <>
To:     Linus Torvalds <>
Cc:     Robin Murphy <>,
        Toke Høiland-Jørgensen <>,
        Christoph Hellwig <>,
        Halil Pasic <>,
        Oleksandr Natalenko <>,
        Marek Szyprowski <>,
        Kalle Valo <>,
        "David S. Miller" <>,
        Jakub Kicinski <>,
        Paolo Abeni <>,
        Olha Cherevyk <>,
        iommu <>,
        linux-wireless <>,
        Netdev <>,
        Linux Kernel Mailing List <>,
        Greg Kroah-Hartman <>,
        stable <>
Subject: Re: [REGRESSION] Recent swiotlb DMA_FROM_DEVICE fixes break
 ath9k-based AP

On Fri, Mar 25, 2022 at 11:46:09AM -0700, Linus Torvalds wrote:
> I think my list of three different sync cases (not just two! It's not
> just about whether to sync for the CPU or the device, it's also about
> what direction the data itself is taking) is correct.
> But maybe I'm wrong.

At the high level you are correct.  It is all about which direction
the data is taking.  That is the direction argument that all the
map/unmap/sync call take.  The sync calls then just toggle the ownership.
You seem to hate that ownership concept, but I don't see how things
could work without that ownership concept as we're going to be in
trouble without having that.  And yes, a peek operation could work in
some cases, but it would have to be at the cache line granularity.

arch/arc/mm/dma.c has a really good comment how these transfers relate
to actual cache operations btw>

 *          |   map          ==  for_device     |   unmap     ==  for_cpu
 *          |----------------------------------------------------------------
 * TO_DEV   |   writeback        writeback      |   none          none
 * FROM_DEV |   invalidate       invalidate     |   invalidate*	  invalidate*
 * BIDIR    |   writeback+inv    writeback+inv  |   invalidate    invalidate
 *     [*] needed for CPU speculative prefetches

Powered by blists - more mailing lists