linux-kernel - Re: [PATCH v2 4/4] misc: fastrpc: Allocate entire reserved memory for Audio PD in probe

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Message-ID: <pm7lequ6lqrgu3mloytfph5opz6aynaa4ag6uedc62fprpskoz@qqvonfthnk6n>
Date: Tue, 3 Feb 2026 23:19:39 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Jianping <jianping.li@....qualcomm.com>
Cc: srini@...nel.org, amahesh@....qualcomm.com, arnd@...db.de,
        gregkh@...uxfoundation.org, linux-arm-msm@...r.kernel.org,
        thierry.escande@...aro.org, abelvesa@...nel.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        quic_chennak@...cinc.com, Ekansh Gupta <ekansh.gupta@....qualcomm.com>
Subject: Re: [PATCH v2 4/4] misc: fastrpc: Allocate entire reserved memory
 for Audio PD in probe

On Mon, Feb 02, 2026 at 03:06:59PM +0800, Jianping wrote:
> 
> 
> On 1/16/2026 4:49 AM, Dmitry Baryshkov wrote:
> > On Thu, Jan 15, 2026 at 04:28:51PM +0800, Jianping Li wrote:
> > > The entire reserved-memory region is now assigned to DSP VMIDs during
> > > channel setup and stored in cctx->remote_heap. Memory is reclaimed in
> > > rpmsg_remove by revoking DSP permissions and freeing the buffer, tying
> > > heap lifecycle to the rpmsg channel.
> > 
> > > @@ -1370,8 +1346,15 @@ static int fastrpc_init_create_static_process(struct fastrpc_user *fl,
> > >   	args[1].length = inbuf.namelen;
> > >   	args[1].fd = -1;
> > > -	pages[0].addr = fl->cctx->remote_heap->dma_addr;
> > > -	pages[0].size = fl->cctx->remote_heap->size;
> > > +	if (!fl->cctx->audio_init_mem) {
> > > +		pages[0].addr = fl->cctx->remote_heap->dma_addr;
> > > +		pages[0].size = fl->cctx->remote_heap->size;
> > 
> > Do we need a flag? Can't we assume that remote_heap is always to be
> > allocated to the PD?
> We do need the audio_init_mem flag.
> Once the PD starts and daemon takes the memory for the first time, PD will
> start using the memory,
> meanwhile, the daemon can be killed and restarted. In this case, the memory
> is still with the PD and the next
> daemon connection should not take any memory for the next request. This flag
> is maintained to ensure that.
> The memory needs to be resent only if Audio PD on DSP restarts(due to
> PD-restart or Subsystem-restart)

This needs to be explained in the changelog.

> 
> > 
> > > +		fl->cctx->audio_init_mem = true;

What if there are two racing IOCTLs, trying to init AudioPD process?

> > > +		inbuf.pageslen = 1;
> > > +	} else {
> > > +		pages[0].addr = 0;
> > > +		pages[0].size = 0;
> > > +	}
> > >   	args[2].ptr = (u64)(uintptr_t) pages;
> > >   	args[2].length = sizeof(*pages);

-- 
With best wishes
Dmitry