linux-kernel - Re: [PATCH v2 1/1] iommu/vt-d: Add Kconfig option to enable/disable scalable mode

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Date:   Mon, 11 Nov 2019 09:27:42 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Qian Cai <cai@....pw>
Cc:     baolu.lu@...ux.intel.com, Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>, kevin.tian@...el.com,
        ashok.raj@...el.com, linux-kernel@...r.kernel.org,
        iommu@...ts.linux-foundation.org, jacob.jun.pan@...el.com
Subject: Re: [PATCH v2 1/1] iommu/vt-d: Add Kconfig option to enable/disable
 scalable mode

Hi,

On 11/9/19 11:59 AM, Qian Cai wrote:
> 
> 
>> On Nov 8, 2019, at 10:40 PM, Lu Baolu <baolu.lu@...ux.intel.com> wrote:
>>
>> This adds Kconfig option INTEL_IOMMU_SCALABLE_MODE_DEFAULT_ON
>> to make it easier for distributions to enable or disable the
>> Intel IOMMU scalable mode by default during kernel build.
>>
>> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
>> ---
>> drivers/iommu/Kconfig       | 9 +++++++++
>> drivers/iommu/intel-iommu.c | 7 ++++++-
>> 2 files changed, 15 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
>> index e3842eabcfdd..fbdf3fd291d9 100644
>> --- a/drivers/iommu/Kconfig
>> +++ b/drivers/iommu/Kconfig
>> @@ -242,6 +242,15 @@ config INTEL_IOMMU_FLOPPY_WA
>> 	  workaround will setup a 1:1 mapping for the first
>> 	  16MiB to make floppy (an ISA device) work.
>>
>> +config INTEL_IOMMU_SCALABLE_MODE_DEFAULT_ON
>> +	prompt "Enable Intel IOMMU scalable mode by default"
>> +	depends on INTEL_IOMMU
>> +	help
>> +	  Selecting this option will enable the scalable mode if
>> +	  hardware presents the capability. If this option is not
>> +	  selected, scalable mode support could also be enabled
>> +	  by passing intel_iommu=sm_on to the kernel.
> 
> 
> Maybe a sentence or two to describe what the scalable mode is in layman's
> terms could be useful, so developers don’t need to search around for the
> Kconfig selection?

How about "pasid based multiple stages DMA translation"?

Best regards,
baolu

> 
>> +
>> config IRQ_REMAP
>> 	bool "Support for Interrupt Remapping"
>> 	depends on X86_64 && X86_IO_APIC && PCI_MSI && ACPI
>> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
>> index 6db6d969e31c..6051fe790c61 100644
>> --- a/drivers/iommu/intel-iommu.c
>> +++ b/drivers/iommu/intel-iommu.c
>> @@ -355,9 +355,14 @@ static phys_addr_t intel_iommu_iova_to_phys(struct iommu_domain *domain,
>> int dmar_disabled = 0;
>> #else
>> int dmar_disabled = 1;
>> -#endif /*CONFIG_INTEL_IOMMU_DEFAULT_ON*/
>> +#endif /* CONFIG_INTEL_IOMMU_DEFAULT_ON */
>>
>> +#ifdef INTEL_IOMMU_SCALABLE_MODE_DEFAULT_ON
>> +int intel_iommu_sm = 1;
>> +#else
>> int intel_iommu_sm;
>> +#endif /* INTEL_IOMMU_SCALABLE_MODE_DEFAULT_ON */
>> +
>> int intel_iommu_enabled = 0;
>> EXPORT_SYMBOL_GPL(intel_iommu_enabled);
>>
>> -- 
>> 2.17.1
>>
>> _______________________________________________
>> iommu mailing list
>> iommu@...ts.linux-foundation.org
>> https://lists.linuxfoundation.org/mailman/listinfo/iommu
> 
> 

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