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

[Tian, Kevin]

> From: Auger Eric <eric.auger@xxxxxxxxxx>
> Sent: Monday, March 30, 2020 12:05 AM
> 
> On 3/28/20 11:01 AM, Tian, Kevin wrote:
> >> From: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> >> 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.
> >
> >> 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@xxxxxxxxxxxxxxx>
> >> Signed-off-by: Ashok Raj <ashok.raj@xxxxxxxxx>
> >> Signed-off-by: Liu, Yi L <yi.l.liu@xxxxxxxxx>
> >> ---
> >>  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"
> >
> >> + *
> >> + * 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.
> >
> >> +	/* 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.
> I tend to agree here.
> >
> >> +	{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?
> I asked the same question some time ago. If I remember correctly the
> issue is while a granu can be supported in inv_type_granu_map, the
> associated value in inv_type_granu_table can be 0. This typically
> matches both values of G field (0 or 1) in the invalidation cmd. See
> other comment below.

I didn't fully understand it. Also what does a value '0' imply? also
it's interesting to see below in [PATCH 07/11]:

+/* QI Dev-IOTLB inv granu */
+#define QI_DEV_IOTLB_GRAN_ALL		1
+#define QI_DEV_IOTLB_GRAN_PASID_SEL	0
+

> >
> >> +	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?
> >
> >> +	}
> >> +	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.
> >
> >> +				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?
> >
> >> +			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 the result of to_vtd_granularity() so it can take either of the
> 2 values.

yes, you're right. 

> 
> Thanks
> 
> Eric
> >
> >> +			} 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
> >
> >> +			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
> >