linux-kernel - Re: [PATCH] drivers/perf: xgene_pmu: Fix uninitialized resource struct

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Date:   Fri, 11 Sep 2020 17:08:04 +0100
From:   Will Deacon <will@...nel.org>
To:     Mark Salter <msalter@...hat.com>
Cc:     Mark Rutland <mark.rutland@....com>,
        Khuong Dinh <khuong@...amperecomputing.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drivers/perf: xgene_pmu: Fix uninitialized resource
 struct

On Tue, Sep 08, 2020 at 02:37:22PM -0400, Mark Salter wrote:
> On Mon, 2020-09-07 at 14:50 +0100, Will Deacon wrote:
> > On Wed, Sep 02, 2020 at 02:27:29PM -0400, Mark Salter wrote:
> > > diff --git a/drivers/perf/xgene_pmu.c b/drivers/perf/xgene_pmu.c
> > > index edac28cd25dd..fdbbd0804b92 100644
> > > --- a/drivers/perf/xgene_pmu.c
> > > +++ b/drivers/perf/xgene_pmu.c
> > > @@ -1483,6 +1483,7 @@ xgene_pmu_dev_ctx *acpi_get_pmu_hw_inf(struct xgene_pmu *xgene_pmu,
> > >  		return NULL;
> > >  
> > >  	INIT_LIST_HEAD(&resource_list);
> > > +	memset(&res, 0, sizeof(res));
> > >  	rc = acpi_dev_get_resources(adev, &resource_list,
> > >  				    acpi_pmu_dev_add_resource, &res);
> > >  	acpi_dev_free_resource_list(&resource_list);
> > 
> > Hmm, to be honest, I'm not sure we should be calling devm_ioremap_resource()
> > at all here. The resource is clearly bogus, even with this change: the name
> > and the resource hierarchy pointers will all be NULL. I think it would be
> > better to follow the TX2 PMU driver (drivers/perf/thunderx2_pmu.c) which
> > appears to assign the resource directly in tx2_uncore_pmu_init_dev().
> > 
> > Is there a reason we can't do that?
> > 
> > Will
> > 
> 
> There's no difference between xgene and tx2 wrt resouce name/hierarchy.
> They both call devm_ioresource_remap() which ends up setting the name
> and hierarchy. The difference is that xgene calls acpi_dev_resource_memory()
> directly from the acpi_dev_get_resources() callback. TX2 doesn't use such a
> callback and in that case, acpi_dev_resource_memory() gets called with a
> zeroed struct.
> 
> That said, changing xgene to avoid the callback like TX2 does would fix the
> problem as well. If you'd rather go that route, I can send a patch for it.

Yes please

Will