> From: Lu Baolu <baolu...@linux.intel.com>
> Sent: Friday, September 24, 2021 10:30 AM
>
> The IOMMU VT-d implementation uses the first level for GPA->HPA
> translation
> by default. Although both the first level and the second level could handle
> the DMA translation, they are different in some way. For example, the
> second
> level translation has separate controls for the Access/Dirty page tracking
> and the page-level forcing snoop. With first level translation, there're
> no such controls. This uses the second level for GPA->HPA translation so
first-level has no page-granular snoop control, but has a global control
in pasid entry.
> that it could provide a consistent hardware interface for use cases like
> dirty page tracking during the VM live migration.
>
> Signed-off-by: Lu Baolu <baolu...@linux.intel.com>
> ---
> include/linux/intel-iommu.h | 7 ++-----
> drivers/iommu/intel/iommu.c | 21 +++++++++++++--------
> 2 files changed, 15 insertions(+), 13 deletions(-)
>
> diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
> index 05a65eb155f7..a5fb20702201 100644
> --- a/include/linux/intel-iommu.h
> +++ b/include/linux/intel-iommu.h
> @@ -517,22 +517,19 @@ struct context_entry {
> u64 hi;
> };
>
> -/* si_domain contains mulitple devices */
> -#define DOMAIN_FLAG_STATIC_IDENTITY BIT(0)
this is a separate cleanup. better mention it in the commit msg or
put in another patch.
> -
> /*
> * When VT-d works in the scalable mode, it allows DMA translation to
> * happen through either first level or second level page table. This
> * bit marks that the DMA translation for the domain goes through the
> * first level page table, otherwise, it goes through the second level.
> */
> -#define DOMAIN_FLAG_USE_FIRST_LEVEL BIT(1)
> +#define DOMAIN_FLAG_USE_FIRST_LEVEL BIT(0)
>
> /*
> * Domain represents a virtual machine which demands iommu nested
> * translation mode support.
> */
> -#define DOMAIN_FLAG_NESTING_MODE BIT(2)
> +#define DOMAIN_FLAG_NESTING_MODE BIT(1)
>
> struct dmar_domain {
> int nid; /* node id */
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index d75f59ae28e6..c814fea0522e 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -522,7 +522,7 @@ static inline void free_devinfo_mem(void *vaddr)
>
> static inline int domain_type_is_si(struct dmar_domain *domain)
> {
> - return domain->flags & DOMAIN_FLAG_STATIC_IDENTITY;
> + return domain->domain.type == IOMMU_DOMAIN_IDENTITY;
> }
>
> static inline bool domain_use_first_level(struct dmar_domain *domain)
> @@ -1874,12 +1874,18 @@ static void free_dmar_iommu(struct
> intel_iommu *iommu)
> * Check and return whether first level is used by default for
> * DMA translation.
> */
> -static bool first_level_by_default(void)
> +static bool first_level_by_default(unsigned int type)
> {
> - return scalable_mode_support() && intel_cap_flts_sanity();
> + if (type == IOMMU_DOMAIN_UNMANAGED)
> + return false;
> +
I think the order is not correct. what about 2nd level is even not
present?
> + if (!scalable_mode_support() || !intel_cap_flts_sanity())
> + return false;
> +
> + return true;
> }
>
> -static struct dmar_domain *alloc_domain(int flags)
> +static struct dmar_domain *alloc_domain(unsigned int type)
> {
> struct dmar_domain *domain;
>
> @@ -1889,8 +1895,7 @@ static struct dmar_domain *alloc_domain(int flags)
>
> memset(domain, 0, sizeof(*domain));
> domain->nid = NUMA_NO_NODE;
> - domain->flags = flags;
> - if (first_level_by_default())
> + if (first_level_by_default(type))
> domain->flags |= DOMAIN_FLAG_USE_FIRST_LEVEL;
> domain->has_iotlb_device = false;
> INIT_LIST_HEAD(&domain->devices);
> @@ -2708,7 +2713,7 @@ static int __init si_domain_init(int hw)
> struct device *dev;
> int i, nid, ret;
>
> - si_domain = alloc_domain(DOMAIN_FLAG_STATIC_IDENTITY);
> + si_domain = alloc_domain(IOMMU_DOMAIN_IDENTITY);
> if (!si_domain)
> return -EFAULT;
>
> @@ -4517,7 +4522,7 @@ static struct iommu_domain
> *intel_iommu_domain_alloc(unsigned type)
> case IOMMU_DOMAIN_DMA:
> case IOMMU_DOMAIN_DMA_FQ:
> case IOMMU_DOMAIN_UNMANAGED:
> - dmar_domain = alloc_domain(0);
> + dmar_domain = alloc_domain(type);
> if (!dmar_domain) {
> pr_err("Can't allocate dmar_domain\n");
> return NULL;
> --
> 2.25.1
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