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Date: Tue, 4 Oct 2016 00:26:17 +0200
From: "Edgar E. Iglesias" <edgar.iglesias@gmail.com>
Message-ID: <20161003222617.GA11832@toto>
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Subject: Re: [Qemu-devel] [PATCH] Reducing stack frame size in
 stream_process_mem2s()
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To: Rutuja Shah <rutu.shah.26@gmail.com>
Cc: qemu-devel@nongnu.org, alistair.francis@xilinx.com, qemu-arm@nongnu.org, Stefan Hajnoczi <stefanha@gmail.com>

On Mon, Oct 03, 2016 at 10:32:40PM +0530, Rutuja Shah wrote:
> ++ stefan Sorry for the typo.
> Regards
> Rutuja Shah
> 
> 
> On Mon, Oct 3, 2016 at 10:26 PM,  <rutu.shah.26@gmail.com> wrote:
> > From: Rutuja Shah <rutu.shah.26@gmail.com>
> >
> > This patch allocates memory for txbuf array on the heap rather than the stack.
> > As a result, the stack frame size is reduced.
> >
> > Signed-off-by: Rutuja Shah <rutu.shah.26@gmail.com>
> > ---
> >  hw/dma/xilinx_axidma.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/hw/dma/xilinx_axidma.c b/hw/dma/xilinx_axidma.c
> > index b135a5f..6c63575 100644
> > --- a/hw/dma/xilinx_axidma.c
> > +++ b/hw/dma/xilinx_axidma.c
> > @@ -256,13 +256,14 @@ static void stream_process_mem2s(struct Stream *s, StreamSlave *tx_data_dev,
> >                                   StreamSlave *tx_control_dev)
> >  {
> >      uint32_t prev_d;
> > -    unsigned char txbuf[16 * 1024];
> > +    unsigned char *txbuf;
> >      unsigned int txlen;
> >
> >      if (!stream_running(s) || stream_idle(s)) {
> >          return;
> >      }
> >
> > +    txbuf = g_malloc(16 * 1024);

Hi,

Two comments.

We need to move the allocation from the data-path to initialization of the DMA objects. (e.g put txbuf into the Stream struct)
We also need to fix up the use of sizeof txbuf.

Best regards,
Edgar


> >      while (1) {
> >          stream_desc_load(s, s->regs[R_CURDESC]);
> >
> > @@ -304,6 +305,7 @@ static void stream_process_mem2s(struct Stream *s, StreamSlave *tx_data_dev,
> >              break;
> >          }
> >      }
> > +    g_free(txbuf);
> >  }
> >
> >  static size_t stream_process_s2mem(struct Stream *s, unsigned char *buf,
> > --
> > 1.9.1
> >