RE: [PATCH v2 1/1] remoteproc: correct rproc_free_vring() to avoid invalid kernel paging

[Loic PALLARDY]

Hi Suman,

> -----Original Message-----
> From: Suman Anna <s-anna@xxxxxx>
> Sent: Thursday, July 26, 2018 12:09 AM
> To: Loic PALLARDY <loic.pallardy@xxxxxx>; bjorn.andersson@xxxxxxxxxx;
> ohad@xxxxxxxxxx
> Cc: linux-remoteproc@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> Arnaud POULIQUEN <arnaud.pouliquen@xxxxxx>;
> benjamin.gaignard@xxxxxxxxxx
> Subject: Re: [PATCH v2 1/1] remoteproc: correct rproc_free_vring() to avoid
> invalid kernel paging
> 
> Hi Loic,
> 
> On 07/06/2018 02:46 AM, Loic Pallardy wrote:
> > If rproc_start() failed, rproc_resource_cleanup() is called to clean
> > debugfs entries, then associated iommu mappings, carveouts and vdev.
> > Issue occurs when rproc_free_vring() is trying to reset vring resource
> > table entry.
> > At this time, table_ptr is pointing on loaded resource table and carveouts
> > already released, so access to loaded resource table is generating a kernel
> > paging error:
> 
> Are you using a device specific CMA pool or carveout, and if so, where
> the pool is? If not, where is the default CMA pool? I am trying to
> reproduce the issue on my platform with the start failure as you
> suggested, but haven't seen it so far. That said, I have seen the exact
> same crash when using HighMEM CMA pools on my downstream kernel
> when
> stopping the processor, and the root cause is essentially the same as
> what you summarized here. The issue was present with LowMem pools as
> well, but got masked because of the kernel linear mapping.

I have a carveout declared in firmware resource table for co-processor code and data, and st driver has a specific 
reserved memory region to fit fix address space requested by co-processor.
So CPU access to code and loaded resource table area is granted thanks to allocation done by rproc_handle_carveout().

> 
> >
> > [   12.696535] Unable to handle kernel paging request at virtual address
> f0f357cc
> > [   12.696540] pgd = (ptrval)
> > [   12.696542] [f0f357cc] *pgd=6d2d0811, *pte=00000000, *ppte=00000000
> > [   12.696558] Internal error: Oops: 807 [#1] SMP ARM
> > [   12.696563] Modules linked in: rpmsg_core v4l2_mem2mem
> videobuf2_dma_contig sti_drm v4l2_common vida
> > [   12.696598] CPU: 1 PID: 48 Comm: kworker/1:1 Tainted: G        W
> 4.18.0-rc2-00018-g3170fdd-8
> > [   12.696602] Hardware name: STi SoC with Flattened Device Tree
> > [   12.696625] Workqueue: events request_firmware_work_func
> > [   12.696659] PC is at rproc_free_vring+0x84/0xbc [remoteproc]
> > [   12.696667] LR is at rproc_free_vring+0x70/0xbc [remoteproc]
> >
> > This patch proposes to simply remove reset of resource table vring entries,
> > as firmware and resource table are reloaded at each rproc boot.
> > rproc_trigger_recovery() not impacted as resources not touched during
> recovery
> > procedure.
> 
> And error recovery doesn't work for me after the rproc_start, stop got
> introduced.
Recovery no available on B2260, but I'll test it on another platform this week

Regards,
Loic
> 
> regards
> Suman
> 
> >
> > Signed-off-by: Loic Pallardy <loic.pallardy@xxxxxx>
> > ---
> > Changes from V1: typo fixes in commit message
> >
> >  drivers/remoteproc/remoteproc_core.c | 6 ------
> >  1 file changed, 6 deletions(-)
> >
> > diff --git a/drivers/remoteproc/remoteproc_core.c
> b/drivers/remoteproc/remoteproc_core.c
> > index a9609d9..9a8b47c 100644
> > --- a/drivers/remoteproc/remoteproc_core.c
> > +++ b/drivers/remoteproc/remoteproc_core.c
> > @@ -289,16 +289,10 @@ void rproc_free_vring(struct rproc_vring *rvring)
> >  {
> >  	int size = PAGE_ALIGN(vring_size(rvring->len, rvring->align));
> >  	struct rproc *rproc = rvring->rvdev->rproc;
> > -	int idx = rvring->rvdev->vring - rvring;
> > -	struct fw_rsc_vdev *rsc;
> >
> >  	dma_free_coherent(rproc->dev.parent, size, rvring->va, rvring-
> >dma);
> >  	idr_remove(&rproc->notifyids, rvring->notifyid);
> >
> > -	/* reset resource entry info */
> > -	rsc = (void *)rproc->table_ptr + rvring->rvdev->rsc_offset;
> > -	rsc->vring[idx].da = 0;
> > -	rsc->vring[idx].notifyid = -1;
> >  }
> >
> >  static int rproc_vdev_do_probe(struct rproc_subdev *subdev)
> >