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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Sun, 27 Mar 2022 17:37:24 -0700
Message-ID: <CAHk-=whScWZnR_DZ12grwOcH_WnU1hJ_YXFmU5GNqrBkhiKgPQ@mail.gmail.com>
Subject: Re: [REGRESSION] Recent swiotlb DMA_FROM_DEVICE fixes break
 ath9k-based AP
To:     Halil Pasic <pasic@linux.ibm.com>
Cc:     =?UTF-8?B?VG9rZSBIw7hpbGFuZC1Kw7hyZ2Vuc2Vu?= <toke@toke.dk>,
        Robin Murphy <robin.murphy@arm.com>,
        Christoph Hellwig <hch@lst.de>,
        Maxime Bizon <mbizon@freebox.fr>,
        Oleksandr Natalenko <oleksandr@natalenko.name>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Kalle Valo <kvalo@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Olha Cherevyk <olha.cherevyk@gmail.com>,
        iommu <iommu@lists.linux-foundation.org>,
        linux-wireless <linux-wireless@vger.kernel.org>,
        Netdev <netdev@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable <stable@vger.kernel.org>
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On Sun, Mar 27, 2022 at 4:37 PM Halil Pasic <pasic@linux.ibm.com> wrote:
>
>
> For the record, I believe that the partial revert proposed here
> https://www.spinics.net/lists/linux-wireless/msg222300.html
> would have been a wiser choice, than a complete revert of commit
> aa6f8dcbab47 ("swiotlb: rework "fix info leak with DMA_FROM_DEVICE"").

Yeah, the revert is basically my standard "this doesn't work,
discussion is still ongoing" thing.

I agree that the revert then brought back that DMA_ATTR_SKIP_CPU_SYNC
complexity.

So that part of commit aa6f8dcbab47 was probably all good.

I somehow missed that Oleksandr had a tested-by for that smaller change too.

              Linus