linux-kernel - Re: [PATCH v14 08/10] iommu/arm-smmu-v3: Add in-kernel support for NVIDIA Tegra241 (Grace) CMDQV

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Message-ID: <e8ab846f-e3ed-403e-af5b-492153a632ce@stanley.mountain>
Date: Wed, 4 Sep 2024 21:47:37 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Nicolin Chen <nicolinc@...dia.com>
Cc: will@...nel.org, robin.murphy@....com, joro@...tes.org, jgg@...dia.com,
	thierry.reding@...il.com, vdumpa@...dia.com, jonathanh@...dia.com,
	linux-kernel@...r.kernel.org, iommu@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org, linux-tegra@...r.kernel.org
Subject: Re: [PATCH v14 08/10] iommu/arm-smmu-v3: Add in-kernel support for
 NVIDIA Tegra241 (Grace) CMDQV

On Wed, Sep 04, 2024 at 10:39:30AM -0700, Nicolin Chen wrote:
> On Wed, Sep 04, 2024 at 08:12:19PM +0300, Dan Carpenter wrote:
>  
> > On Wed, Sep 04, 2024 at 08:17:11AM -0700, Nicolin Chen wrote:
> > > Hi Dan,
> > >
> > > On Wed, Sep 04, 2024 at 10:29:26AM +0300, Dan Carpenter wrote:
> > >
> > > > I was reviewing Smatch warnings:
> > > >
> > > >     drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c:616 tegra241_cmdqv_init_vintf()
> > > >     error: Calling ida_alloc_max() with a 'max' argument which is a power of 2. -1 missing?
> > > >
> > > > The problem is that we're calling ida_alloc_max() where max is always zero.
> > > >
> > > > > +static int tegra241_cmdqv_init_vintf(struct tegra241_cmdqv *cmdqv, u16 max_idx,
> > > > > +                                  struct tegra241_vintf *vintf)
> > > > > +{
> > > > > +
> > > > > +     u16 idx;
> > > > > +     int ret;
> > > > > +
> > > > > +     ret = ida_alloc_max(&cmdqv->vintf_ids, max_idx, GFP_KERNEL);
> > > > > +     if (ret < 0)
> > > > > +             return ret;
> > > > > +     idx = ret;
> > > >
> > > > max_idx is always zero so idx is always zero.
> > >
> > > There is a followup series adding support for max[1, max_vintf].
> > > And I guess that would make Smatch happy. I'd personally prefer
> > > keep this by ignoring the Smatch warning. But if you think the
> > > common practice is to drop it and add back, I'd be okay with it.
> > >
> > 
> > I'm just reviewing static checker warnings so I don't know the back story...
> > How long are we going to have to wait for the follow on patchset?
> 
> There are a couple of dependencies we need to get merged first.
> So, it might take a few months I think.
> 
> Perhaps I can make a small patch by changing the ida_alloc_max
> in the common place here to iad_alloc_range(.., 1, max,..) in
> the caller of the followup series. Then the existing caller for
> vintf0 wouldn't need an ida_alloc().

Nah, forget about it.  We can wait for a few months.

regards,
dan carpenter