Messages in this thread Patch in this message | | | Date | Sat, 6 Apr 2024 20:55:44 +0800 | From | Baolu Lu <> | Subject | Re: [PATCH 01/12] iommu/vt-d: Add cache tag assignment interface |
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Hi Kevin,
Thanks for your review comments.
On 3/28/24 3:12 PM, Tian, Kevin wrote: >> From: Lu Baolu <baolu.lu@linux.intel.com> >> Sent: Monday, March 25, 2024 10:17 AM >> >> +enum cache_tag_type { >> + CACHE_TAG_TYPE_IOTLB, >> + CACHE_TAG_TYPE_DEVTLB, >> + CACHE_TAG_TYPE_PARENT_IOTLB, >> + CACHE_TAG_TYPE_PARENT_DEVTLB, >> +}; > > '_TYPE_' can be removed to make it shorter
Okay.
> >> + >> +/* Checks if an existing cache tag can be reused for a new association. */ >> +static bool cache_tag_reusable(struct cache_tag *tag, u16 domain_id, >> + struct intel_iommu *iommu, struct device *dev, >> + ioasid_t pasid, enum cache_tag_type type) > > cache_tage_match()
Okay.
> >> +{ >> + if (tag->type != type) >> + return false; >> + >> + if (tag->domain_id != domain_id || tag->pasid != pasid) >> + return false; >> + >> + if (type == CACHE_TAG_TYPE_IOTLB) >> + return tag->iommu == iommu; >> + >> + if (type == CACHE_TAG_TYPE_DEVTLB) >> + return tag->dev == dev; >> + >> + return false; > > why do you disallow PARENT_TYPE from reusing? It's not uncommon > to have two devices attached to a same nested domain hence with > the same parent domain. Disallowing tag reuse implies unnecessarily > duplicated cache flushes...
PARENT_TYPE could be reused. The new helper looks like the following:
/* Checks if an existing cache tag can be reused for a new association. */ static bool cache_tage_match(struct cache_tag *tag, u16 domain_id, struct intel_iommu *iommu, struct device *dev, ioasid_t pasid, enum cache_tag_type type) { if (tag->type != type) return false;
if (tag->domain_id != domain_id || tag->pasid != pasid) return false;
if (type == CACHE_TAG_IOTLB || type == CACHE_TAG_PARENT_IOTLB) return tag->iommu == iommu;
if (type == CACHE_TAG_DEVTLB || type == CACHE_TAG_PARENT_DEVTLB) return tag->dev == dev;
return false; }
>> +} >> + >> +/* Assign a cache tag with specified type to domain. */ >> +static int cache_tag_assign(struct dmar_domain *domain, u16 did, >> + struct device *dev, ioasid_t pasid, >> + enum cache_tag_type type) >> +{ >> + struct device_domain_info *info = dev_iommu_priv_get(dev); >> + struct intel_iommu *iommu = info->iommu; >> + struct cache_tag *tag, *temp; >> + unsigned long flags; >> + >> + tag = kzalloc(sizeof(*tag), GFP_KERNEL); >> + if (!tag) >> + return -ENOMEM; >> + >> + tag->type = type; >> + tag->iommu = iommu; >> + tag->dev = dev; > > should we set tag->dev only for DEVTLB type? It's a bit confusing to set > it for IOTLB type which doesn't care about device. Actually doing so > is instead misleading as the 1st device creating the tag may have been > detached but then it will still show up in the trace when the last device > detach destroying the tag.
For IOTLB types, perhaps we could add a struct device pointer for the iommu. This way, the tag->dev could more directly indicate the device implementing the cache.
> >> +static int __cache_tag_assign_parent_domain(struct dmar_domain >> *domain, u16 did, >> + struct device *dev, ioasid_t pasid) > > this pair is similar to the earlier one except the difference on type. > > what about keeping just one pair which accepts a 'parent' argument to > decide the type internally?
Okay, let try to refine it.
> > >> +/* >> + * Assigns cache tags to a domain when it's associated with a device's >> + * PASID using a specific domain ID. > > s/Assigns/Assign/
Done.
> >> + >> + did = domain_id_iommu(domain, iommu); >> + ret = cache_tag_assign_domain(domain, did, dev, >> IOMMU_NO_PASID); > > there are many occurrences of this pattern. What about passing in > a 'iommu' parameter and getting 'did' inside the helper? for svm > it can be specialized internally too.
Perhaps, let me try it later and see what the code looks like.
> >> @@ -4607,10 +4623,11 @@ static void >> intel_iommu_remove_dev_pasid(struct device *dev, ioasid_t pasid) >> */ >> if (domain->type == IOMMU_DOMAIN_SVA) { >> intel_svm_remove_dev_pasid(dev, pasid); >> + cache_tag_unassign_domain(dmar_domain, >> + FLPT_DEFAULT_DID, dev, pasid); > > is it correct to destroy the tag before teardown completes, e.g. iotlb still > needs to be flushed in intel_pasid_tear_down_entry()?
You are right. iotlb still needs to be there until the teardown completes. I will investigate this more later.
Beset regards, baolu
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