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

[Lu Baolu]

Hi Yi,

On 12/20/19 7:44 PM, Liu, Yi L wrote:
> > From: Lu Baolu [mailto:baolu.lu@xxxxxxxxxxxxxxx]
> > Sent: Thursday, December 19, 2019 11:17 AM
> > To: Joerg Roedel <joro@xxxxxxxxxx>; David Woodhouse <dwmw2@xxxxxxxxxxxxx>;
> > Alex Williamson <alex.williamson@xxxxxxxxxx>
> > 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@xxxxxxxxxxxxxxx>
> > ---
> >   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