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SubjectRe: [PATCH 1/3] iommu/vt-d: Remove redundant IOTLB flush
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On 2020/3/21 0:20, Jacob Pan wrote:
> On Fri, 20 Mar 2020 21:45:26 +0800
> Lu Baolu <baolu.lu@linux.intel.com> wrote:
>
>> On 2020/3/20 12:32, Jacob Pan wrote:
>>> IOTLB flush already included in the PASID tear down process. There
>>> is no need to flush again.
>>
>> It seems that intel_pasid_tear_down_entry() doesn't flush the pasid
>> based device TLB?
>>
> I saw this code in intel_pasid_tear_down_entry(). Isn't the last line
> flush the devtlb? Not in guest of course since the passdown tlb flush
> is inclusive.
>
> pasid_cache_invalidation_with_pasid(iommu, did, pasid);
> iotlb_invalidation_with_pasid(iommu, did, pasid);
>
> /* Device IOTLB doesn't need to be flushed in caching mode. */
> if (!cap_caching_mode(iommu->cap))
> devtlb_invalidation_with_pasid(iommu, dev, pasid);
>

But devtlb_invalidation_with_pasid() doesn't do the right thing, it
flushes the device tlb, instead of pasid-based device tlb.

static void
devtlb_invalidation_with_pasid(struct intel_iommu *iommu,
struct device *dev, int pasid)
{
struct device_domain_info *info;
u16 sid, qdep, pfsid;

info = dev->archdata.iommu;
if (!info || !info->ats_enabled)
return;

sid = info->bus << 8 | info->devfn;
qdep = info->ats_qdep;
pfsid = info->pfsid;

qi_flush_dev_iotlb(iommu, sid, pfsid, qdep, 0, 64 -
VTD_PAGE_SHIFT);
}

Best regards,
baolu

>> Best regards,
>> baolu
>>
>>>
>>> Cc: Lu Baolu <baolu.lu@linux.intel.com>
>>> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
>>> ---
>>> drivers/iommu/intel-svm.c | 6 ++----
>>> 1 file changed, 2 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
>>> index 8f42d717d8d7..1483f1845762 100644
>>> --- a/drivers/iommu/intel-svm.c
>>> +++ b/drivers/iommu/intel-svm.c
>>> @@ -268,10 +268,9 @@ static void intel_mm_release(struct
>>> mmu_notifier *mn, struct mm_struct *mm)
>>> * *has* to handle gracefully without affecting other
>>> processes. */
>>> rcu_read_lock();
>>> - list_for_each_entry_rcu(sdev, &svm->devs, list) {
>>> + list_for_each_entry_rcu(sdev, &svm->devs, list)
>>> intel_pasid_tear_down_entry(svm->iommu,
>>> sdev->dev, svm->pasid);
>>> - intel_flush_svm_range_dev(svm, sdev, 0, -1, 0);
>>> - }
>>> +
>>> rcu_read_unlock();
>>>
>>> }
>>> @@ -731,7 +730,6 @@ int intel_svm_unbind_mm(struct device *dev, int
>>> pasid)
>>> * large and has to be physically
>>> contiguous. So it's
>>> * hard to be as defensive as we might
>>> like. */ intel_pasid_tear_down_entry(iommu, dev, svm->pasid);
>>> - intel_flush_svm_range_dev(svm, sdev, 0,
>>> -1, 0); kfree_rcu(sdev, rcu);
>>>
>>> if (list_empty(&svm->devs)) {
>>>
>
> [Jacob Pan]
>

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