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SubjectRe: [PATCH 4/5] iommu/vt-d: Remove domain_update_iommu_snooping()
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On 2022/5/3 05:36, Jacob Pan wrote:
> 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 */

It has been cleaned up by below commit:

71cfafda9c9b vfio: Move the Intel no-snoop control off of IOMMU_CACHE

>
>> 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

Best regards,
baolu

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