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References: <20220627190120.176470-1-ivan.malov@oktetlabs.ru> <20220628091848.534803-1-ivan.malov@oktetlabs.ru>
In-Reply-To: <20220628091848.534803-1-ivan.malov@oktetlabs.ru>
From:   Magnus Karlsson <magnus.karlsson@gmail.com>
Date:   Tue, 28 Jun 2022 11:29:18 +0200
Message-ID: <CAJ8uoz1Ha=aOfF8+ttJLcU3nyCJBpUUyKk27rzKbPGx10oD6qQ@mail.gmail.com>
Subject: Re: [PATCH net v3 1/1] xsk: clear page contiguity bit when unmapping pool
To:     Ivan Malov <ivan.malov@oktetlabs.ru>
Cc:     Magnus Karlsson <magnus.karlsson@intel.com>,
        =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn.topel@intel.com>,
        Network Development <netdev@vger.kernel.org>,
        Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>,
        bpf <bpf@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
        =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn@kernel.org>,
        Maciej Fijalkowski <maciej.fijalkowski@intel.com>,
        Jonathan Lemon <jonathan.lemon@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Jesper Dangaard Brouer <hawk@kernel.org>,
        John Fastabend <john.fastabend@gmail.com>,
        Maxim Mikityanskiy <maximmi@mellanox.com>
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On Tue, Jun 28, 2022 at 11:25 AM Ivan Malov <ivan.malov@oktetlabs.ru> wrote:
>
> When a XSK pool gets mapped, xp_check_dma_contiguity() adds bit 0x1
> to pages' DMA addresses that go in ascending order and at 4K stride.
> The problem is that the bit does not get cleared before doing unmap.
> As a result, a lot of warnings from iommu_dma_unmap_page() are seen
> in dmesg, which indicates that lookups by iommu_iova_to_phys() fail.
>
> Fixes: 2b43470add8c ("xsk: Introduce AF_XDP buffer allocation API")
> Signed-off-by: Ivan Malov <ivan.malov@oktetlabs.ru>

Thanks Ivan.

Acked-by: Magnus Karlsson <magnus.karlsson@intel.com>

> ---
>  v1 -> v2: minor adjustments to dispose of the "Fixes:" tag warning
>  v2 -> v3: extra refinements to apply notes from Magnus Karlsson
>
>  net/xdp/xsk_buff_pool.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c
> index 87bdd71c7bb6..f70112176b7c 100644
> --- a/net/xdp/xsk_buff_pool.c
> +++ b/net/xdp/xsk_buff_pool.c
> @@ -332,6 +332,7 @@ static void __xp_dma_unmap(struct xsk_dma_map *dma_map, unsigned long attrs)
>         for (i = 0; i < dma_map->dma_pages_cnt; i++) {
>                 dma = &dma_map->dma_pages[i];
>                 if (*dma) {
> +                       *dma &= ~XSK_NEXT_PG_CONTIG_MASK;
>                         dma_unmap_page_attrs(dma_map->dev, *dma, PAGE_SIZE,
>                                              DMA_BIDIRECTIONAL, attrs);
>                         *dma = 0;
> --
> 2.30.2
>