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SubjectRe: [PATCH v4 4/7] iommu/vt-d: Setup pasid entries for iova over first level
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Hi Yi,

On 12/20/19 7:44 PM, Liu, Yi L wrote:
>> From: Lu Baolu [mailto:baolu.lu@linux.intel.com]
>> Sent: Thursday, December 19, 2019 11:17 AM
>> To: Joerg Roedel <joro@8bytes.org>; David Woodhouse <dwmw2@infradead.org>;
>> Alex Williamson <alex.williamson@redhat.com>
>> Subject: [PATCH v4 4/7] iommu/vt-d: Setup pasid entries for iova over first level
>>
>> Intel VT-d in scalable mode supports two types of page tables for IOVA translation:
>> first level and second level. The IOMMU driver can choose one from both for IOVA
>> translation according to the use case. This sets up the pasid entry if a domain is
>> selected to use the first-level page table for iova translation.
>>
>> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
>> ---
>> drivers/iommu/intel-iommu.c | 48 +++++++++++++++++++++++++++++++++++--
>> include/linux/intel-iommu.h | 16 ++++++++-----
>> 2 files changed, 56 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c index
>> 2b5a47584baf..f0813997dea2 100644
>> --- a/drivers/iommu/intel-iommu.c
>> +++ b/drivers/iommu/intel-iommu.c
>> @@ -571,6 +571,11 @@ static inline int domain_type_is_si(struct dmar_domain
>> *domain)
>> return domain->flags & DOMAIN_FLAG_STATIC_IDENTITY; }
>>
>> +static inline bool domain_use_first_level(struct dmar_domain *domain) {
>> + return domain->flags & DOMAIN_FLAG_USE_FIRST_LEVEL; }
>> +
>> static inline int domain_pfn_supported(struct dmar_domain *domain,
>> unsigned long pfn)
>> {
>> @@ -2288,6 +2293,8 @@ static int __domain_mapping(struct dmar_domain
>> *domain, unsigned long iov_pfn,
>> return -EINVAL;
>>
>> prot &= DMA_PTE_READ | DMA_PTE_WRITE | DMA_PTE_SNP;
>> + if (domain_use_first_level(domain))
>> + prot |= DMA_FL_PTE_PRESENT | DMA_FL_PTE_XD;
>>
>> if (!sg) {
>> sg_res = nr_pages;
>> @@ -2515,6 +2522,36 @@ dmar_search_domain_by_dev_info(int segment, int bus,
>> int devfn)
>> return NULL;
>> }
>>
>> +static int domain_setup_first_level(struct intel_iommu *iommu,
>> + struct dmar_domain *domain,
>> + struct device *dev,
>> + int pasid)
>> +{
>> + int flags = PASID_FLAG_SUPERVISOR_MODE;
>
> Hi Baolu,
>
> Could you explain a bit why PASID_FLAG_SUPERVISOR_MODE is
> required?
>

This flag indicates a PASID which can be used for access to kernel
addresses (static 1:1 only). Otherwise, DMA requests requesting
supervisor level privilege level will be blocked.

> Regards,
> Yi Liu
>

Best regards,
baolu

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