linux-kernel - Re: [PATCH v8 2/7] iommu: Move global PASID allocation from SVA to core

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Date:   Tue, 11 Jul 2023 07:32:28 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     Baolu Lu <baolu.lu@...ux.intel.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, iommu@...ts.linux.dev,
        Jason Gunthorpe <jgg@...dia.com>,
        Joerg Roedel <joro@...tes.org>,
        Robin Murphy <robin.murphy@....com>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        dmaengine@...r.kernel.org, vkoul@...nel.org,
        Will Deacon <will@...nel.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Raj Ashok <ashok.raj@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>, Yi Liu <yi.l.liu@...el.com>,
        "Yu, Fenghua" <fenghua.yu@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        "Zanussi, Tom" <tom.zanussi@...el.com>, rex.zhang@...el.com,
        xiaochen.shen@...el.com, narayan.ranganathan@...el.com,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH v8 2/7] iommu: Move global PASID allocation from SVA to
 core

Hi Baolu,

On Sat, 10 Jun 2023 20:13:03 +0800, Baolu Lu <baolu.lu@...ux.intel.com>
wrote:

> On 6/3/23 2:22 AM, Jacob Pan wrote:
> > +ioasid_t iommu_alloc_global_pasid_dev(struct device *dev)
> > +{
> > +	int ret;
> > +	ioasid_t max;
> > +
> > +	max = dev->iommu->max_pasids;
> > +	/*
> > +	 * max_pasids is set up by vendor driver based on number of
> > PASID bits
> > +	 * supported but the IDA allocation is inclusive.
> > +	 */
> > +	ret = ida_alloc_range(&iommu_global_pasid_ida,
> > IOMMU_FIRST_GLOBAL_PASID, max - 1, GFP_KERNEL);
> > +	if (ret < 0)
> > +		return IOMMU_PASID_INVALID;
> > +
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL_GPL(iommu_alloc_global_pasid_dev);  
> 
> "dev->iommu->max_pasids == 0" indicates no pasid support on the device.
> The code should return IOMMU_PASID_INVALID explicitly. Perhaps we can
> make this function like this:
> 
> ioasid_t iommu_alloc_global_pasid_dev(struct device *dev)
> {
>          int ret;
> 
>          if (!dev->iommu->max_pasids)
>                  return IOMMU_PASID_INVALID;
> 
>          /*
>           * max_pasids is set up by vendor driver based on number of 
> PASID bits
>           * supported but the IDA allocation is inclusive.
>           */
>          ret = ida_alloc_range(&iommu_global_pasid_ida, 
> IOMMU_FIRST_GLOBAL_PASID,
>                                dev->iommu->max_pasids - 1, GFP_KERNEL);
> 
>          return ret < 0 ? IOMMU_PASID_INVALID : ret;
> }
> EXPORT_SYMBOL_GPL(iommu_alloc_global_pasid_dev);
> 
good catch, sorry i missed this. let me send an updated version.

> Other change in this series looks good to me.
> 
> I hope I can queue this series including above change as part of my VT-d
> update for v6.5 to Joerg if no objection.
> 
> Let's try to re-enable this key feature of Intel idxd driver in v6.5.
> 
> Best regards,
> baolu


Thanks,

Jacob