linux-kernel - Re: [PATCH v2 1/5] iommu: Return -EMEDIUMTYPE for incompatible domain and device/group

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Date:   Wed, 15 Jun 2022 19:40:02 -0700
From:   Nicolin Chen <nicolinc@...dia.com>
To:     Baolu Lu <baolu.lu@...ux.intel.com>
CC:     <joro@...tes.org>, <will@...nel.org>, <marcan@...can.st>,
        <sven@...npeter.dev>, <robin.murphy@....com>,
        <robdclark@...il.com>, <matthias.bgg@...il.com>,
        <orsonzhai@...il.com>, <baolin.wang7@...il.com>,
        <zhang.lyra@...il.com>, <jean-philippe@...aro.org>,
        <alex.williamson@...hat.com>, <jgg@...dia.com>,
        <kevin.tian@...el.com>, <suravee.suthikulpanit@....com>,
        <alyssa@...enzweig.io>, <dwmw2@...radead.org>,
        <yong.wu@...iatek.com>, <mjrosato@...ux.ibm.com>,
        <gerald.schaefer@...ux.ibm.com>, <thierry.reding@...il.com>,
        <vdumpa@...dia.com>, <jonathanh@...dia.com>, <cohuck@...hat.com>,
        <thunder.leizhen@...wei.com>, <tglx@...utronix.de>,
        <christophe.jaillet@...adoo.fr>, <john.garry@...wei.com>,
        <chenxiang66@...ilicon.com>, <saiprakash.ranjan@...eaurora.org>,
        <isaacm@...eaurora.org>, <yangyingliang@...wei.com>,
        <jordan@...micpenguin.net>, <iommu@...ts.linux-foundation.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-arm-msm@...r.kernel.org>,
        <linux-mediatek@...ts.infradead.org>, <linux-s390@...r.kernel.org>,
        <linux-tegra@...r.kernel.org>,
        <virtualization@...ts.linux-foundation.org>, <kvm@...r.kernel.org>
Subject: Re: [PATCH v2 1/5] iommu: Return -EMEDIUMTYPE for incompatible
 domain and device/group

On Thu, Jun 16, 2022 at 10:09:49AM +0800, Baolu Lu wrote:
> External email: Use caution opening links or attachments
> 
> 
> On 2022/6/16 08:03, Nicolin Chen wrote:
> > diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> > index 44016594831d..0dd13330fe12 100644
> > --- a/drivers/iommu/intel/iommu.c
> > +++ b/drivers/iommu/intel/iommu.c
> > @@ -4323,7 +4323,7 @@ static int prepare_domain_attach_device(struct iommu_domain *domain,
> >               return -ENODEV;
> > 
> >       if (dmar_domain->force_snooping && !ecap_sc_support(iommu->ecap))
> > -             return -EOPNOTSUPP;
> > +             return -EMEDIUMTYPE;
> > 
> >       /* check if this iommu agaw is sufficient for max mapped address */
> >       addr_width = agaw_to_width(iommu->agaw);
> > @@ -4331,10 +4331,10 @@ static int prepare_domain_attach_device(struct iommu_domain *domain,
> >               addr_width = cap_mgaw(iommu->cap);
> > 
> >       if (dmar_domain->max_addr > (1LL << addr_width)) {
> > -             dev_err(dev, "%s: iommu width (%d) is not "
> > +             dev_dbg(dev, "%s: iommu width (%d) is not "
> >                       "sufficient for the mapped address (%llx)\n",
> >                       __func__, addr_width, dmar_domain->max_addr);
> > -             return -EFAULT;
> > +             return -EMEDIUMTYPE;
> >       }
> >       dmar_domain->gaw = addr_width;
> 
> Can we simply remove the dev_err()? As the return value has explicitly
> explained the failure reason, putting a print statement won't help much.

Yes. As long as no one has objection, I can remove that in the next
version.