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SubjectRe: [RFC PATCH v2 02/10] iommu/vt-d: Add multiple domains per device query
On Thu, 30 Aug 2018 12:09:14 +0800
Lu Baolu <baolu.lu@linux.intel.com> wrote:

> Add the response to IOMMU_CAP_AUX_DOMAIN capability query
> through iommu_capable(). Return true if IOMMUs support the
> scalable mode, return false otherwise.
>
> Cc: Ashok Raj <ashok.raj@intel.com>
> Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
> Cc: Kevin Tian <kevin.tian@intel.com>
> Cc: Liu Yi L <yi.l.liu@intel.com>
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> ---
> drivers/iommu/intel-iommu.c | 31 +++++++++++++++++++++++++++++--
> 1 file changed, 29 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 3e49d4029058..891ae70e7bf2 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -5193,12 +5193,39 @@ static phys_addr_t intel_iommu_iova_to_phys(struct iommu_domain *domain,
> return phys;
> }
>
> +static inline bool scalable_mode_support(void)
> +{
> + struct dmar_drhd_unit *drhd;
> + struct intel_iommu *iommu;
> + bool ret = true;
> +
> + rcu_read_lock();
> + for_each_active_iommu(iommu, drhd) {
> + if (!sm_supported(iommu)) {
> + ret = false;
> + break;
> + }
> + }
> + rcu_read_unlock();
> +
> + return ret;
> +}
> +
> static bool intel_iommu_capable(enum iommu_cap cap)
> {
> - if (cap == IOMMU_CAP_CACHE_COHERENCY)
> + switch (cap) {
> + case IOMMU_CAP_CACHE_COHERENCY:
> return domain_update_iommu_snooping(NULL) == 1;
> - if (cap == IOMMU_CAP_INTR_REMAP)
> + case IOMMU_CAP_INTR_REMAP:
> return irq_remapping_enabled == 1;
> + case IOMMU_CAP_AUX_DOMAIN:
> + return scalable_mode_support();
> + case IOMMU_CAP_NOEXEC:
> + /* PASSTHROUGH */
> + default:
> + pr_info("Unsupported capability query %d\n", cap);
> + break;

Please don't do this, there's no reason to be noisy about a query of a
capability that VT-d doesn't know about. We implement capabilities
exactly so that relevant drivers can expose a feature and others can
happily (and quietly) ignore them. Thanks,

Alex

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