> From: Lu Baolu <baolu...@linux.intel.com>
> Sent: Sunday, September 26, 2021 7:46 PM
>
> 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're different in some way. For example, the second
> level translation has separate controls for the Access/Dirty page tracking.
> With the first level translation, there's no such control. On the other
> hand, the second level translation has the page-level control for forcing
> snoop, but the first level only has global control with pasid granularity.
>
> This uses the second level for GPA->HPA translation so that we can provide
> a consistent hardware interface for use cases like dirty page tracking for
> live migration.
>
> Signed-off-by: Lu Baolu <baolu...@linux.intel.com>
> ---
> drivers/iommu/intel/iommu.c | 12 +++++++++---
> 1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index dc2030d014e0..426630261614 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -1991,9 +1991,15 @@ 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();
/* Only SL is available in legacy mode */
> + if (!scalable_mode_support())
> + return false;
> +
/* if only level (either FL or SL) is available, just use it */
> + if (intel_cap_flts_sanity() ^ intel_cap_slts_sanity())
> + return intel_cap_flts_sanity();
> +
/* if both levels are available, decide it based on domain type */
> + return type != IOMMU_DOMAIN_UNMANAGED;
> }
with above comments added:
Reviewed-by: Kevin Tian <kevin.t...@intel.com>
>
> static struct dmar_domain *alloc_domain(unsigned int type)
> @@ -2006,7 +2012,7 @@ static struct dmar_domain
> *alloc_domain(unsigned int type)
>
> memset(domain, 0, sizeof(*domain));
> domain->nid = NUMA_NO_NODE;
> - 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);
> --
> 2.25.1
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