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From: Lu Baolu <baolu.lu@linux.intel.com>
To: Leon Romanovsky <leon@kernel.org>
Cc: baolu.lu@linux.intel.com, 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: Sat, 16 Jan 2021 16:47:40 +0800	[thread overview]
Message-ID: <eda6ae9f-76eb-3254-ce58-ea355418a4b1@linux.intel.com> (raw)
In-Reply-To: <20210116083904.GN944463@unreal>

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.

Best regards,
baolu

  reply	other threads:[~2021-01-16  8:49 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 [this message]
2021-01-17  5:30               ` Leon Romanovsky
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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