From: Leon Romanovsky <leon@kernel.org> To: Lu Baolu <baolu.lu@linux.intel.com> Cc: tglx@linutronix.de, ashok.raj@intel.com, kevin.tian@intel.com, dave.jiang@intel.com, megha.dey@intel.com, dwmw2@infradead.org, alex.williamson@redhat.com, bhelgaas@google.com, dan.j.williams@intel.com, will@kernel.org, joro@8bytes.org, dmaengine@vger.kernel.org, eric.auger@redhat.com, jacob.jun.pan@intel.com, jgg@mellanox.com, kvm@vger.kernel.org, kwankhede@nvidia.com, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, iommu@lists.linux-foundation.org, maz@kernel.org, mona.hossain@intel.com, netanelg@mellanox.com, parav@mellanox.com, pbonzini@redhat.com, rafael@kernel.org, samuel.ortiz@intel.com, sanjay.k.kumar@intel.com, shahafs@mellanox.com, tony.luck@intel.com, vkoul@kernel.org, yan.y.zhao@linux.intel.com, yi.l.liu@intel.com Subject: Re: [RFC PATCH v3 1/2] iommu: Add capability IOMMU_CAP_VIOMMU Date: Sun, 17 Jan 2021 07:30:39 +0200 [thread overview] Message-ID: <20210117053039.GO944463@unreal> (raw) In-Reply-To: <eda6ae9f-76eb-3254-ce58-ea355418a4b1@linux.intel.com> On Sat, Jan 16, 2021 at 04:47:40PM +0800, Lu Baolu wrote: > Hi Leon, > > On 2021/1/16 16:39, Leon Romanovsky wrote: > > On Sat, Jan 16, 2021 at 09:20:16AM +0800, Lu Baolu wrote: > > > Hi, > > > > > > On 2021/1/15 14:31, Leon Romanovsky wrote: > > > > On Fri, Jan 15, 2021 at 07:49:47AM +0800, Lu Baolu wrote: > > > > > Hi Leon, > > > > > > > > > > On 1/14/21 9:26 PM, Leon Romanovsky wrote: > > > > > > On Thu, Jan 14, 2021 at 09:30:02AM +0800, Lu Baolu wrote: > > > > > > > Some vendor IOMMU drivers are able to declare that it is running in a VM > > > > > > > context. This is very valuable for the features that only want to be > > > > > > > supported on bare metal. Add a capability bit so that it could be used. > > > > > > > > > > > > And how is it used? Who and how will set it? > > > > > > > > > > Use the existing iommu_capable(). I should add more descriptions about > > > > > who and how to use it. > > > > > > > > I want to see the code that sets this capability. > > > > > > Currently we have Intel VT-d and the virt-iommu setting this capability. > > > > > > static bool intel_iommu_capable(enum iommu_cap cap) > > > { > > > if (cap == IOMMU_CAP_CACHE_COHERENCY) > > > return domain_update_iommu_snooping(NULL) == 1; > > > if (cap == IOMMU_CAP_INTR_REMAP) > > > return irq_remapping_enabled == 1; > > > + if (cap == IOMMU_CAP_VIOMMU) > > > + return caching_mode_enabled(); > > > > > > return false; > > > } > > > > > > And, > > > > > > +static bool viommu_capable(enum iommu_cap cap) > > > +{ > > > + if (cap == IOMMU_CAP_VIOMMU) > > > + return true; > > > + > > > + return false; > > > +} > > > > These two functions are reading this cap and not setting. > > Where can I see code that does "cap = IOMMU_CAP_VIOMMU" and not "=="? > > The iommu_capable() is a generic IOMMU interface to query IOMMU > capabilities. It takes @bus and @cap as input, and calls the callback > of vendor iommu. If the vendor iommu driver supports the specific > capability, it returns true. Otherwise, it returns false. > > bool iommu_capable(struct bus_type *bus, enum iommu_cap cap) > { > if (!bus->iommu_ops || !bus->iommu_ops->capable) > return false; > > return bus->iommu_ops->capable(cap); > } > EXPORT_SYMBOL_GPL(iommu_capable); > > In the vendor iommu's callback, it checks the capability and returns a > value according to its capability, just as showed above. Ohh, sorry. I missed "iommu_capable(dev->bus, IOMMU_CAP_VIOMMU)" from second patch. Thanks > > Best regards, > baolu
next prev parent reply other threads:[~2021-01-17 5:31 UTC|newest] Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-01-14 1:30 [RFC PATCH v3 0/2] Add platform check for subdevice irq domain Lu Baolu 2021-01-14 1:30 ` [RFC PATCH v3 1/2] iommu: Add capability IOMMU_CAP_VIOMMU Lu Baolu 2021-01-14 13:26 ` Leon Romanovsky 2021-01-14 23:49 ` Lu Baolu 2021-01-15 6:31 ` Leon Romanovsky 2021-01-16 1:20 ` Lu Baolu 2021-01-16 8:39 ` Leon Romanovsky 2021-01-16 8:47 ` Lu Baolu 2021-01-17 5:30 ` Leon Romanovsky [this message] 2021-01-15 4:46 ` Jason Wang 2021-01-14 1:30 ` [RFC PATCH v3 2/2] platform-msi: Add platform check for subdevice irq domain Lu Baolu 2021-01-14 3:03 ` Tian, Kevin
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