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SubjectRe: [PATCH 4/5] iommu/vt-d: Remove domain_update_iommu_snooping()
Hi BaoLu,

On Sun, 1 May 2022 19:24:33 +0800, Lu Baolu <baolu.lu@linux.intel.com>
wrote:

> The IOMMU force snooping capability is not required to be consistent
> among all the IOMMUs anymore. Remove force snooping capability check
> in the IOMMU hot-add path and domain_update_iommu_snooping() becomes
> a dead code now.
>
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> ---
> drivers/iommu/intel/iommu.c | 34 +---------------------------------
> 1 file changed, 1 insertion(+), 33 deletions(-)
>
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 3c1c228f9031..d5808495eb64 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -533,33 +533,6 @@ static void domain_update_iommu_coherency(struct
> dmar_domain *domain) rcu_read_unlock();
> }
>
> -static bool domain_update_iommu_snooping(struct intel_iommu *skip)
> -{
> - struct dmar_drhd_unit *drhd;
> - struct intel_iommu *iommu;
> - bool ret = true;
> -
> - rcu_read_lock();
> - for_each_active_iommu(iommu, drhd) {
> - if (iommu != skip) {
> - /*
> - * If the hardware is operating in the scalable
> mode,
> - * the snooping control is always supported
> since we
> - * always set PASID-table-entry.PGSNP bit if the
> domain
> - * is managed outside (UNMANAGED).
> - */
> - if (!sm_supported(iommu) &&
> - !ecap_sc_support(iommu->ecap)) {
> - ret = false;
> - break;
> - }
> - }
> - }
> - rcu_read_unlock();
> -
> - return ret;
> -}
> -
> static int domain_update_iommu_superpage(struct dmar_domain *domain,
> struct intel_iommu *skip)
> {
> @@ -3593,12 +3566,7 @@ static int intel_iommu_add(struct dmar_drhd_unit
> *dmaru) iommu->name);
> return -ENXIO;
> }
> - if (!ecap_sc_support(iommu->ecap) &&
> - domain_update_iommu_snooping(iommu)) {
> - pr_warn("%s: Doesn't support snooping.\n",
> - iommu->name);
> - return -ENXIO;
> - }
> +
Maybe I missed earlier patches, so this bit can also be deleted?

struct dmar_domain {
u8 iommu_snooping: 1; /* indicate snooping control
feature */

> sp = domain_update_iommu_superpage(NULL, iommu) - 1;
> if (sp >= 0 && !(cap_super_page_val(iommu->cap) & (1 << sp))) {
> pr_warn("%s: Doesn't support large page.\n",


Thanks,

Jacob

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