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From: Peter Maydell <peter.maydell@linaro.org>
Date: Mon, 8 Oct 2018 13:30:20 +0100
Message-ID: <CAFEAcA9_EOFV=5i-4S1GWVgewAa89hJDTegnf9Ot3w7rfkZWYA@mail.gmail.com>
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Subject: Re: [Qemu-devel] [PATCH v1 06/12] net: cadence_gem: Add support for
 selecting the DMA MemoryRegion
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To: "Edgar E. Iglesias" <edgar.iglesias@gmail.com>
Cc: QEMU Developers <qemu-devel@nongnu.org>, qemu-arm <qemu-arm@nongnu.org>, Richard Henderson <richard.henderson@linaro.org>, KONRAD Frederic <frederic.konrad@adacore.com>, Alistair Francis <alistair@alistair23.me>, Francisco Iglesias <frasse.iglesias@gmail.com>, figlesia@xilinx.com, Stefano Stabellini <sstabellini@kernel.org>, Sai Pavan Boddu <sai.pavan.boddu@xilinx.com>, Edgar Iglesias <edgar.iglesias@xilinx.com>

On 3 October 2018 at 16:07, Edgar E. Iglesias <edgar.iglesias@gmail.com> wrote:
> From: "Edgar E. Iglesias" <edgar.iglesias@xilinx.com>
>
> Add support for selecting the Memory Region that the GEM
> will do DMA to.
>
> Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
> ---
>  hw/net/cadence_gem.c         | 63 ++++++++++++++++++++++++++++----------------
>  include/hw/net/cadence_gem.h |  2 ++
>  2 files changed, 43 insertions(+), 22 deletions(-)
>
> diff --git a/hw/net/cadence_gem.c b/hw/net/cadence_gem.c
> index 759c1d7..ab02515 100644
> --- a/hw/net/cadence_gem.c
> +++ b/hw/net/cadence_gem.c
> @@ -28,6 +28,7 @@
>  #include "hw/net/cadence_gem.h"
>  #include "qapi/error.h"
>  #include "qemu/log.h"
> +#include "sysemu/dma.h"
>  #include "net/checksum.h"
>
>  #ifdef CADENCE_GEM_ERR_DEBUG
> @@ -835,9 +836,9 @@ static void gem_get_rx_desc(CadenceGEMState *s, int q)
>  {
>      DB_PRINT("read descriptor 0x%x\n", (unsigned)s->rx_desc_addr[q]);
>      /* read current descriptor */
> -    cpu_physical_memory_read(s->rx_desc_addr[q],
> -                             (uint8_t *)s->rx_desc[q],
> -                             sizeof(uint32_t) * gem_get_desc_len(s, true));
> +    address_space_read(s->dma_as, s->rx_desc_addr[q], MEMTXATTRS_UNSPECIFIED,
> +                       (uint8_t *)s->rx_desc[q],
> +                       sizeof(uint32_t) * gem_get_desc_len(s, true));

At some point you might want to add support for handling "descriptor
read/write failed", incidentally: address_space_read/write return a
MemTxResult which you can check for != MEMTX_OK.

thanks
-- PMM