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

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Date:   Thu, 16 Jun 2022 10:09:49 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     Nicolin Chen <nicolinc@...dia.com>, 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
Cc:     baolu.lu@...ux.intel.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 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.

Best regards,
baolu