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

[Tian, Kevin]

> From: Auger Eric <eric.auger@xxxxxxxxxx>
> Sent: Sunday, March 29, 2020 11:34 PM
> 
> Hi,
> 
> 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.
> Isn't it the same when G=1? Still the addr/size is used. Doesn't it

I thought addr/size is not used when G=1, but it might be wrong. I'm
checking with our vt-d spec owner.

> correspond to IOMMU_INV_GRANU_ADDR with
> IOMMU_INV_ADDR_FLAGS_PASID flag
> unset?
> 
> so {0, 0, 1}?

I have one more open:

How does userspace know which invalidation type/gran is supported?
I didn't see such capability reporting in Yi's VFIO vSVA patch set. Do we
want the user/kernel assume the same capability set if they are 
architectural? However the kernel could also do some optimization
e.g. hide devtlb invalidation capability given that the kernel already 
invalidate devtlb automatically when serving iotlb invalidation...

Thanks
Kevin

> 
> Thanks
> 
> Eric
> 
> >
> >> +	/* 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.
> >
> >> +	{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?
> >
> >> +	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?
> >
> >> +			} 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
> >