linux-kernel - Re: [PATCH v2 02/16] iommu/vt-d: add bind_pasid

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Date:   Thu, 12 Oct 2017 10:38:51 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     "Liu, Yi L" <yi.l.liu@...el.com>
Cc:     "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        "David Woodhouse" <dwmw2@...radead.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        Jean-Philippe Brucker <jean-philippe.brucker@....com>,
        "Lan, Tianyu" <tianyu.lan@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Yi L <yi.l.liu@...ux.intel.com>, jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH v2 02/16] iommu/vt-d: add bind_pasid_table function

On Thu, 12 Oct 2017 11:12:46 +0000
"Liu, Yi L" <yi.l.liu@...el.com> wrote:

> > From: Jacob Pan [mailto:jacob.jun.pan@...ux.intel.com]
> > Sent: Friday, October 6, 2017 7:04 AM
> > To: iommu@...ts.linux-foundation.org; LKML
> > <linux-kernel@...r.kernel.org>; Joerg Roedel <joro@...tes.org>;
> > David Woodhouse <dwmw2@...radead.org>; Greg Kroah-Hartman
> > <gregkh@...uxfoundation.org>; Wysocki, Rafael J
> > <rafael.j.wysocki@...el.com>; Jean-Philippe Brucker <jean-
> > philippe.brucker@....com> Cc: Liu, Yi L <yi.l.liu@...el.com>; Lan,
> > Tianyu <tianyu.lan@...el.com>; Tian, Kevin <kevin.tian@...el.com>;
> > Raj, Ashok <ashok.raj@...el.com>; Alex Williamson
> > <alex.williamson@...hat.com>; Jacob Pan
> > <jacob.jun.pan@...ux.intel.com>; Liu; Yi L
> > <yi.l.liu@...ux.intel.com> Subject: [PATCH v2 02/16] iommu/vt-d:
> > add bind_pasid_table function
> > 
> > Add Intel VT-d ops to the generic iommu_bind_pasid_table API
> > functions.
> > 
> > The primary use case is for direct assignment of SVM capable
> > device. Originated from emulated IOMMU in the guest, the request
> > goes through many layers (e.g. VFIO). Upon calling host IOMMU
> > driver, caller passes guest PASID table pointer (GPA) and size.
> > 
> > Device context table entry is modified by Intel IOMMU specific
> > bind_pasid_table function. This will turn on nesting mode and
> > matching translation type.
> > 
> > The unbind operation restores default context mapping.
> > 
> > Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> > Signed-off-by: Liu, Yi L <yi.l.liu@...ux.intel.com>
> > Signed-off-by: Ashok Raj <ashok.raj@...el.com>
> > ---
> >  drivers/iommu/intel-iommu.c   | 117
> > ++++++++++++++++++++++++++++++++++++++++++
> >  include/linux/dma_remapping.h |   1 +
> >  2 files changed, 118 insertions(+)
> > 
> > diff --git a/drivers/iommu/intel-iommu.c
> > b/drivers/iommu/intel-iommu.c index 209d99a..7ae569c 100644
> > --- a/drivers/iommu/intel-iommu.c
> > +++ b/drivers/iommu/intel-iommu.c
> > @@ -5200,6 +5200,7 @@ static void
> > intel_iommu_put_resv_regions(struct device *dev,
> > 
> >  #ifdef CONFIG_INTEL_IOMMU_SVM
> >  #define MAX_NR_PASID_BITS (20)
> > +#define MIN_NR_PASID_BITS (5)
> >  static inline unsigned long intel_iommu_get_pts(struct intel_iommu
> > *iommu)  { /*
> > @@ -5326,6 +5327,118 @@ struct intel_iommu
> > *intel_svm_device_to_iommu(struct device *dev)
> > 
> >  	return iommu;
> >  }
> > +
> > +static int intel_iommu_bind_pasid_table(struct iommu_domain
> > *domain,
> > +		struct device *dev, struct pasid_table_config
> > *pasidt_binfo) {
> > +	struct intel_iommu *iommu;
> > +	struct context_entry *context;
> > +	struct dmar_domain *dmar_domain = to_dmar_domain(domain);
> > +	struct device_domain_info *info;
> > +	struct pci_dev *pdev;
> > +	u8 bus, devfn, host_table_pasid_bits;
> > +	u16 did, sid;
> > +	int ret = 0;
> > +	unsigned long flags;
> > +	u64 ctx_lo;
> > +
> > +	iommu = device_to_iommu(dev, &bus, &devfn);
> > +	if (!iommu)
> > +		return -ENODEV;
> > +	/* VT-d spec 9.4 says pasid table size is encoded as
> > 2^(x+5) */
> > +	host_table_pasid_bits = intel_iommu_get_pts(iommu) +
> > MIN_NR_PASID_BITS;
> > +	if (!pasidt_binfo || pasidt_binfo->pasid_bits >
> > host_table_pasid_bits ||
> > +		pasidt_binfo->pasid_bits < MIN_NR_PASID_BITS) {
> > +		pr_err("Invalid gPASID bits %d, host range %d -
> > %d\n",
> > +			pasidt_binfo->pasid_bits,
> > +			MIN_NR_PASID_BITS, host_table_pasid_bits);
> > +		return -ERANGE;
> > +	}
> > +
> > +	pdev = to_pci_dev(dev);
> > +	if (!pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PRI))
> > +		return -EINVAL;
> > +	sid = PCI_DEVID(bus, devfn);
> > +
> > +	info = dev->archdata.iommu;
> > +	if (!info || !info->pasid_supported) {
> > +		dev_err(dev, "No PASID support\n");
> > +		ret = -EINVAL;
> > +		goto out;
> > +	}
> > +	if (!info->pasid_enabled) {
> > +		ret = pci_enable_pasid(pdev, info->pasid_supported
> > & ~1);
> > +		if (ret)
> > +			goto out;
> > +	}
> > +	if (!device_context_mapped(iommu, bus, devfn)) {
> > +		pr_warn("ctx not mapped for bus devfn %x:%x\n",
> > bus, devfn);
> > +		ret = -EINVAL;
> > +		goto out;
> > +	}  
> 
> [Liu, Yi L] This is checking whether ctx is present. So if it is
> true, then the following 6 line should be always true. Perhaps, a
> merge could be done here with the following 6 lines.
> 
good point, I can do the present check below. no need to hold the lock
twice.
> > +	spin_lock_irqsave(&iommu->lock, flags);
> > +	context = iommu_context_addr(iommu, bus, devfn, 0);
> > +	if (!context) {
> > +		ret = -EINVAL;
> > +		goto out_unlock;
> > +	}
> > +  
> 
> Regards,
> Yi L