RE: [PATCH V10 08/11] iommu/vt-d: Add svm/sva invalidate function

Tian, Kevin
2020-04-01T06:24:34Z

> From: Jacob Pan <jacob.jun.pan@linux.intel.com>
> Sent: Wednesday, April 1, 2020 2:14 AM
>
> On Sat, 28 Mar 2020 10:01:42 +0000
> "Tian, Kevin" <kevin.tian@intel.com> wrote:
>
> > > From: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > > Sent: Saturday, March 21, 2020 7:28 AM
> > >
> > > When Shared Virtual Address (SVA) is enabled for a guest OS via
> > > vIOMMU, we need to provide invalidation support at IOMMU API and
> > > driver level. This patch adds Intel VT-d specific function to
> > > implement iommu passdown invalidate API for shared virtual address.
> > >
> > > The use case is for supporting caching structure invalidation
> > > of assigned SVM capable devices. Emulated IOMMU exposes queue
> >
> > emulated IOMMU -> vIOMMU, since virito-iommu could use the
> > interface as well.
> >
> True, but it does not invalidate this statement about emulated IOMMU. I
> will add another statement saying "the same interface can be used for
> virtio-IOMMU as well". OK?

sure

>
> > > invalidation capability and passes down all descriptors from the
> > > guest to the physical IOMMU.
> > >
> > > The assumption is that guest to host device ID mapping should be
> > > resolved prior to calling IOMMU driver. Based on the device handle,
> > > host IOMMU driver can replace certain fields before submit to the
> > > invalidation queue.
> > >
> > > ---
> > > v7 review fixed in v10
> > > ---
> > >
> > > Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > > Signed-off-by: Ashok Raj <ashok.raj@intel.com>
> > > Signed-off-by: Liu, Yi L <yi.l.liu@intel.com>
> > > ---
> > > drivers/iommu/intel-iommu.c | 182
> > > ++++++++++++++++++++++++++++++++++++++++++++
> > > 1 file changed, 182 insertions(+)
> > >
> > > diff --git a/drivers/iommu/intel-iommu.c
> > > b/drivers/iommu/intel-iommu.c index b1477cd423dd..a76afb0fd51a
> > > 100644 --- a/drivers/iommu/intel-iommu.c
> > > +++ b/drivers/iommu/intel-iommu.c
> > > @@ -5619,6 +5619,187 @@ static void
> > > intel_iommu_aux_detach_device(struct iommu_domain *domain,
> > > aux_domain_remove_dev(to_dmar_domain(domain), dev);
> > > }
> > >
> > > +/*
> > > + * 2D array for converting and sanitizing IOMMU generic TLB
> > > granularity to
> > > + * VT-d granularity. Invalidation is typically included in the
> > > unmap operation
> > > + * as a result of DMA or VFIO unmap. However, for assigned devices
> > > guest
> > > + * owns the first level page tables. Invalidations of translation
> > > caches in the
> > > + * guest are trapped and passed down to the host.
> > > + *
> > > + * vIOMMU in the guest will only expose first level page tables,
> > > therefore
> > > + * we do not include IOTLB granularity for request without PASID
> > > (second level).
> >
> > I would revise above as "We do not support IOTLB granularity for
> > request without PASID (second level), therefore any vIOMMU
> > implementation that exposes the SVA capability to the guest should
> > only expose the first level page tables, implying all invalidation
> > requests from the guest will include a valid PASID"
> >
> Sounds good.
>
> > > + *
> > > + * For example, to find the VT-d granularity encoding for IOTLB
> > > + * type and page selective granularity within PASID:
> > > + * X: indexed by iommu cache type
> > > + * Y: indexed by enum iommu_inv_granularity
> > > + * [IOMMU_CACHE_INV_TYPE_IOTLB][IOMMU_INV_GRANU_ADDR]
> > > + *
> > > + * Granu_map array indicates validity of the table. 1: valid, 0:
> > > invalid
> > > + *
> > > + */
> > > +const static int
> > >
> inv_type_granu_map[IOMMU_CACHE_INV_TYPE_NR][IOMMU_INV_GRANU_
> > > NR] = {
> > > + /*
> > > + * PASID based IOTLB invalidation: PASID selective (per
> > > PASID),
> > > + * page selective (address granularity)
> > > + */
> > > + {0, 1, 1},
> > > + /* PASID based dev TLBs, only support all PASIDs or single
> > > PASID */
> > > + {1, 1, 0},
> >
> > Is this combination correct? when single PASID is being specified, it
> > is essentially a page-selective invalidation since you need provide
> > Address and Size.
> >
> This is for translation between generic UAPI granu to VT-d granu, it
> has nothing to do with address and size.

Generic UAPI defines three granularities: domain, pasid and addr.
from the definition domain applies all entries related to did, pasid
applies to all entries related to pasid, while addr is specific for a
range.

from what we just confirmed internally with VT-d spec owner, our
PASID based dev TLB invalidation always requires addr and size,
while current uAPI doesn't support multiple PASIDs based range
invaliation. It sounds to me that you want to use domain to replace
multiple PASIDs case (G=1), but it then changes the meaning of
the domain granularity and easily lead to confusion.

I feel Eric's proposal makes more sense. Here we'd better use {0, 0, 1}
to indicate only addr range invalidation is allowed, matching the
spec definition. We may use a special flag in iommu_inv_addr_info
to indicate G=1 case, if necessary.

> e.g.
> If user passes IOMMU_INV_GRANU_PASID for the single PASID case as you
> mentioned, this map table shows it is valid.
>
> Then the lookup result will get VT-d granu:
> QI_DEV_IOTLB_GRAN_PASID_SEL, which means G=0.
>
>
> > > + /* PASID cache */
> >
> > PASID cache is fully managed by the host. Guest PASID cache
> > invalidation is interpreted by vIOMMU for bind and unbind operations.
> > I don't think we should accept any PASID cache invalidation from
> > userspace or guest.
> >
>
> True for vIOMMU, this is here for completeness. Can be used by virtio
> IOMMU, since PC flush is inclusive (IOTLB, devTLB), it is more
> efficient.

I think it is not correct in concept. We should not allow the userspace or
guest to request an operation which is beyond its privilege (just because
doing so may bring some performance benefit). You can always introduce
new cmd for such purpose.

>
> > > + {1, 1, 0}
> > > +};
> > > +
> > > +const static int
> > >
> inv_type_granu_table[IOMMU_CACHE_INV_TYPE_NR][IOMMU_INV_GRANU
> > > _NR] = {
> > > + /* PASID based IOTLB */
> > > + {0, QI_GRAN_NONG_PASID, QI_GRAN_PSI_PASID},
> > > + /* PASID based dev TLBs */
> > > + {QI_DEV_IOTLB_GRAN_ALL, QI_DEV_IOTLB_GRAN_PASID_SEL, 0},
> > > + /* PASID cache */
> > > + {QI_PC_ALL_PASIDS, QI_PC_PASID_SEL, 0},
> > > +};
> > > +
> > > +static inline int to_vtd_granularity(int type, int granu, int
> > > *vtd_granu) +{
> > > + if (type >= IOMMU_CACHE_INV_TYPE_NR || granu >=
> > > IOMMU_INV_GRANU_NR ||
> > > + !inv_type_granu_map[type][granu])
> > > + return -EINVAL;
> > > +
> > > + *vtd_granu = inv_type_granu_table[type][granu];
> > > +
> >
> > btw do we really need both map and table here? Can't we just
> > use one table with unsupported granularity marked as a special
> > value?
> >
> Yes, for value = 1. e.g. G=0 but still valid.
>
> > > + return 0;
> > > +}
> > > +
> > > +static inline u64 to_vtd_size(u64 granu_size, u64 nr_granules)
> > > +{
> > > + u64 nr_pages = (granu_size * nr_granules) >>
> > > VTD_PAGE_SHIFT; +
> > > + /* VT-d size is encoded as 2^size of 4K pages, 0 for 4k, 9
> > > for 2MB, etc.
> > > + * IOMMU cache invalidate API passes granu_size in bytes,
> > > and number of
> > > + * granu size in contiguous memory.
> > > + */
> > > + return order_base_2(nr_pages);
> > > +}
> > > +
> > > +#ifdef CONFIG_INTEL_IOMMU_SVM
> > > +static int intel_iommu_sva_invalidate(struct iommu_domain *domain,
> > > + struct device *dev, struct
> > > iommu_cache_invalidate_info *inv_info)
> > > +{
> > > + struct dmar_domain *dmar_domain = to_dmar_domain(domain);
> > > + struct device_domain_info *info;
> > > + struct intel_iommu *iommu;
> > > + unsigned long flags;
> > > + int cache_type;
> > > + u8 bus, devfn;
> > > + u16 did, sid;
> > > + int ret = 0;
> > > + u64 size = 0;
> > > +
> > > + if (!inv_info || !dmar_domain ||
> > > + inv_info->version !=
> > > IOMMU_CACHE_INVALIDATE_INFO_VERSION_1)
> > > + return -EINVAL;
> > > +
> > > + if (!dev || !dev_is_pci(dev))
> > > + return -ENODEV;
> > > +
> > > + iommu = device_to_iommu(dev, &bus, &devfn);
> > > + if (!iommu)
> > > + return -ENODEV;
> > > +
> > > + spin_lock_irqsave(&device_domain_lock, flags);
> > > + spin_lock(&iommu->lock);
> > > + info = iommu_support_dev_iotlb(dmar_domain, iommu, bus,
> > > devfn);
> > > + if (!info) {
> > > + ret = -EINVAL;
> > > + goto out_unlock;
> >
> > -ENOTSUPP?
> >
> I guess it can go either way in that the error is based on invalid
> inputs.
>
> > > + }
> > > + did = dmar_domain->iommu_did[iommu->seq_id];
> > > + sid = PCI_DEVID(bus, devfn);
> > > +
> > > + /* Size is only valid in non-PASID selective invalidation
> > > */
> > > + if (inv_info->granularity != IOMMU_INV_GRANU_PASID)
> > > + size =
> > > to_vtd_size(inv_info->addr_info.granule_size,
> > > +
> > > inv_info->addr_info.nb_granules); +
> > > + for_each_set_bit(cache_type, (unsigned long
> > > *)&inv_info->cache, IOMMU_CACHE_INV_TYPE_NR) {
> > > + int granu = 0;
> > > + u64 pasid = 0;
> > > +
> > > + ret = to_vtd_granularity(cache_type,
> > > inv_info->granularity, &granu);
> > > + if (ret) {
> > > + pr_err("Invalid cache type and granu
> > > combination %d/%d\n", cache_type,
> > > + inv_info->granularity);
> > > + break;
> > > + }
> > > +
> > > + /* PASID is stored in different locations based on
> > > granularity */
> > > + if (inv_info->granularity == IOMMU_INV_GRANU_PASID
> > > &&
> > > + inv_info->pasid_info.flags &
> > > IOMMU_INV_PASID_FLAGS_PASID)
> > > + pasid = inv_info->pasid_info.pasid;
> > > + else if (inv_info->granularity ==
> > > IOMMU_INV_GRANU_ADDR &&
> > > + inv_info->addr_info.flags &
> > > IOMMU_INV_ADDR_FLAGS_PASID)
> > > + pasid = inv_info->addr_info.pasid;
> > > + else {
> > > + pr_err("Cannot find PASID for given cache
> > > type and granularity\n");
> > > + break;
> > > + }
> > > +
> > > + switch (BIT(cache_type)) {
> > > + case IOMMU_CACHE_INV_TYPE_IOTLB:
> > > + if ((inv_info->granularity !=
> > > IOMMU_INV_GRANU_PASID) &&
> >
> > granularity == IOMMU_INV_GRANU_ADDR? otherwise it's unclear
> > why IOMMU_INV_GRANU_DOMAIN also needs size check.
> >
> Good point! will fix.
>
> > > + size && (inv_info->addr_info.addr &
> > > ((BIT(VTD_PAGE_SHIFT + size)) - 1))) {
> > > + pr_err("Address out of range,
> > > 0x%llx, size order %llu\n",
> > > + inv_info->addr_info.addr,
> > > size);
> > > + ret = -ERANGE;
> > > + goto out_unlock;
> > > + }
> > > +
> > > + qi_flush_piotlb(iommu, did,
> > > + pasid,
> > > + mm_to_dma_pfn(inv_info-
> > > >addr_info.addr),
> > > + (granu ==
> > > QI_GRAN_NONG_PASID) ? - 1 : 1 << size,
> > > + inv_info->addr_info.flags &
> > > IOMMU_INV_ADDR_FLAGS_LEAF);
> > > +
> > > + /*
> > > + * Always flush device IOTLB if ATS is
> > > enabled since guest
> > > + * vIOMMU exposes CM = 1, no device IOTLB
> > > flush will be passed
> > > + * down.
> > > + */
> >
> > Does VT-d spec mention that no device IOTLB flush is required when
> > CM=1?
> >
> Not explicitly. Just following the guideline in CH6.1 for efficient
> virtualization. Early on, we also had discussion on supporting virtio
> where IOTLB flush is inclusive.
> Let me rephrase the comment:
> /*
> * Always flush device IOTLB if ATS is enabled. vIOMMU
> * in the guest may assume IOTLB flush is inclusive,
> * which is more efficient.
> */

this looks better.

>
>
> > > + if (info->ats_enabled) {
> > > + qi_flush_dev_iotlb_pasid(iommu,
> > > sid, info-
> > > >pfsid,
> > > + pasid,
> > > info->ats_qdep,
> > > +
> > > inv_info->addr_info.addr, size,
> > > + granu);
> > > + }
> > > + break;
> > > + case IOMMU_CACHE_INV_TYPE_DEV_IOTLB:
> > > + if (info->ats_enabled) {
> > > + qi_flush_dev_iotlb_pasid(iommu,
> > > sid, info-
> > > >pfsid,
> > > +
> > > inv_info->addr_info.pasid, info->ats_qdep,
> > > +
> > > inv_info->addr_info.addr, size,
> > > + granu);
> >
> > I'm confused here. There are two granularities allowed for devtlb,
> > but here you only handle one of them?
> >
> granu is passed into the flush function, which can be 1 or 0.
>
> > > + } else
> > > + pr_warn("Passdown device IOTLB
> > > flush w/o ATS!\n");
> > > +
> > > + break;
> > > + case IOMMU_CACHE_INV_TYPE_PASID:
> > > + qi_flush_pasid_cache(iommu, did, granu,
> > > inv_info-
> > > >pasid_info.pasid);
> > > +
> >
> > as earlier comment, we shouldn't allow userspace or guest to
> > invalidate PASID cache
> >
> same explanation :)
>
> > > + break;
> > > + default:
> > > + dev_err(dev, "Unsupported IOMMU
> > > invalidation type %d\n",
> > > + cache_type);
> > > + ret = -EINVAL;
> > > + }
> > > + }
> > > +out_unlock:
> > > + spin_unlock(&iommu->lock);
> > > + spin_unlock_irqrestore(&device_domain_lock, flags);
> > > +
> > > + return ret;
> > > +}
> > > +#endif
> > > +
> > > static int intel_iommu_map(struct iommu_domain *domain,
> > > unsigned long iova, phys_addr_t hpa,
> > > size_t size, int iommu_prot, gfp_t gfp)
> > > @@ -6204,6 +6385,7 @@ const struct iommu_ops intel_iommu_ops = {
> > > .is_attach_deferred =
> > > intel_iommu_is_attach_deferred, .pgsize_bitmap =
> > > INTEL_IOMMU_PGSIZES, #ifdef CONFIG_INTEL_IOMMU_SVM
> > > + .cache_invalidate = intel_iommu_sva_invalidate,
> > > .sva_bind_gpasid = intel_svm_bind_gpasid,
> > > .sva_unbind_gpasid = intel_svm_unbind_gpasid,
> > > #endif
> > > --
> > > 2.7.4
> >
>
> [Jacob Pan]