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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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