Messages in this thread | | | From | "Tian, Kevin" <> | Subject | RE: [PATCH V10 11/11] iommu/vt-d: Add custom allocator for IOASID | Date | Thu, 2 Apr 2020 02:18:45 +0000 |
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> From: Jacob Pan <jacob.jun.pan@linux.intel.com> > Sent: Wednesday, April 1, 2020 11:48 PM > > On Sat, 28 Mar 2020 10:22:41 +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 VT-d driver runs in the guest, PASID allocation must be > > > performed via virtual command interface. This patch registers a > > > custom IOASID allocator which takes precedence over the default > > > XArray based allocator. The resulting IOASID allocation will always > > > come from the host. This ensures that PASID namespace is system- > > > wide. > > > > > > Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com> > > > Signed-off-by: Liu, Yi L <yi.l.liu@intel.com> > > > Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com> > > > --- > > > drivers/iommu/intel-iommu.c | 84 > > > +++++++++++++++++++++++++++++++++++++++++++++ > > > include/linux/intel-iommu.h | 2 ++ > > > 2 files changed, 86 insertions(+) > > > > > > diff --git a/drivers/iommu/intel-iommu.c > > > b/drivers/iommu/intel-iommu.c index a76afb0fd51a..c1c0b0fb93c3 > > > 100644 --- a/drivers/iommu/intel-iommu.c > > > +++ b/drivers/iommu/intel-iommu.c > > > @@ -1757,6 +1757,9 @@ static void free_dmar_iommu(struct > intel_iommu > > > *iommu) > > > if (ecap_prs(iommu->ecap)) > > > intel_svm_finish_prq(iommu); > > > } > > > + if (ecap_vcs(iommu->ecap) && vccap_pasid(iommu->vccap)) > > > + > > > ioasid_unregister_allocator(&iommu->pasid_allocator); + > > > #endif > > > } > > > > > > @@ -3291,6 +3294,84 @@ static int copy_translation_tables(struct > > > intel_iommu *iommu) > > > return ret; > > > } > > > > > > +#ifdef CONFIG_INTEL_IOMMU_SVM > > > +static ioasid_t intel_ioasid_alloc(ioasid_t min, ioasid_t max, > > > void *data) > > > > the name is too generic... can we add vcmd in the name to clarify > > its purpose, e.g. intel_vcmd_ioasid_alloc? > > > I feel the intel_ prefix is a natural extension of a generic API, we do > that for other IOMMU APIs, right?
other IOMMU APIs have no difference between host and guest, but this one only applies to guest with vcmd interface.
> > > > +{ > > > + struct intel_iommu *iommu = data; > > > + ioasid_t ioasid; > > > + > > > + if (!iommu) > > > + return INVALID_IOASID; > > > + /* > > > + * VT-d virtual command interface always uses the full 20 > > > bit > > > + * PASID range. Host can partition guest PASID range based > > > on > > > + * policies but it is out of guest's control. > > > + */ > > > + if (min < PASID_MIN || max > intel_pasid_max_id) > > > + return INVALID_IOASID; > > > + > > > + if (vcmd_alloc_pasid(iommu, &ioasid)) > > > + return INVALID_IOASID; > > > + > > > + return ioasid; > > > +} > > > + > > > +static void intel_ioasid_free(ioasid_t ioasid, void *data) > > > +{ > > > + struct intel_iommu *iommu = data; > > > + > > > + if (!iommu) > > > + return; > > > + /* > > > + * Sanity check the ioasid owner is done at upper layer, > > > e.g. VFIO > > > + * We can only free the PASID when all the devices are > > > unbound. > > > + */ > > > + if (ioasid_find(NULL, ioasid, NULL)) { > > > + pr_alert("Cannot free active IOASID %d\n", ioasid); > > > + return; > > > + } > > > > However the sanity check is not done in default_free. Is there a > > reason why using vcmd adds such new requirement? > > > Since we don't support nested guest. This vcmd allocator is only used > by the guest IOMMU driver not VFIO. We expect IOMMU driver to have > control of the free()/unbind() ordering. > > For default_free, it can come from user space and host VFIO which can > be out of order. But we will solve that issue with the blocking > notifier. > > > > + vcmd_free_pasid(iommu, ioasid); > > > +} > > > + > > > +static void register_pasid_allocator(struct intel_iommu *iommu) > > > +{ > > > + /* > > > + * If we are running in the host, no need for custom > > > allocator > > > + * in that PASIDs are allocated from the host system-wide. > > > + */ > > > + if (!cap_caching_mode(iommu->cap)) > > > + return; > > > > is it more accurate to check against vcmd capability? > > > I think this is sufficient. The spec says if vcmd is present, we must > use it but not the other way.
No, what about an vIOMMU implementation reports CM but not VCMD? I didn't get the rationale why we check an indirect capability when there is already one well defined for the purpose.
> > > > + > > > + if (!sm_supported(iommu)) { > > > + pr_warn("VT-d Scalable Mode not enabled, no PASID > > > allocation\n"); > > > + return; > > > + } > > > + > > > + /* > > > + * Register a custom PASID allocator if we are running in > > > a guest, > > > + * guest PASID must be obtained via virtual command > > > interface. > > > + * There can be multiple vIOMMUs in each guest but only one > > > allocator > > > + * is active. All vIOMMU allocators will eventually be > > > calling the same > > > > which one? the first or last? > > > All allocators share the same ops, so first=last. IOASID code will > inspect the ops function and see if they are shared with others then > use the same ops.
ok, got you.
> > > > + * host allocator. > > > + */ > > > + if (ecap_vcs(iommu->ecap) && vccap_pasid(iommu->vccap)) { > > > + pr_info("Register custom PASID allocator\n"); > > > + iommu->pasid_allocator.alloc = intel_ioasid_alloc; > > > + iommu->pasid_allocator.free = intel_ioasid_free; > > > + iommu->pasid_allocator.pdata = (void *)iommu; > > > + if > > > (ioasid_register_allocator(&iommu->pasid_allocator)) { > > > + pr_warn("Custom PASID allocator failed, > > > scalable mode disabled\n"); > > > + /* > > > + * Disable scalable mode on this IOMMU if > > > there > > > + * is no custom allocator. Mixing SM > > > capable vIOMMU > > > + * and non-SM vIOMMU are not supported. > > > + */ > > > + intel_iommu_sm = 0; > > > > since you register an allocator for every vIOMMU, means previously > > registered allocators should also be unregistered here? > > > True, but it is not necessary for two reasons: > 1. This should not happen unless something went seriously wrong. > All vIOMMU shares the same alloc/free function, so they are put under > the same bucket by IOASID. So the case for the first vIOMMU to succeed > then fail in later vIOMMU registration should not happen. Unless kernel > run out of memory etc. > > 2. Once SM is disabled, there is no user of ioasid allocator. > > > > + } > > > + } > > > +} > > > +#endif > > > + > > > static int __init init_dmars(void) > > > { > > > struct dmar_drhd_unit *drhd; > > > @@ -3408,6 +3489,9 @@ static int __init init_dmars(void) > > > */ > > > for_each_active_iommu(iommu, drhd) { > > > iommu_flush_write_buffer(iommu); > > > +#ifdef CONFIG_INTEL_IOMMU_SVM > > > + register_pasid_allocator(iommu); > > > +#endif > > > iommu_set_root_entry(iommu); > > > iommu->flush.flush_context(iommu, 0, 0, 0, > > > DMA_CCMD_GLOBAL_INVL); > > > iommu->flush.flush_iotlb(iommu, 0, 0, 0, > > > DMA_TLB_GLOBAL_FLUSH); > > > diff --git a/include/linux/intel-iommu.h > > > b/include/linux/intel-iommu.h index 9cbf5357138b..9c357a325c72 > > > 100644 --- a/include/linux/intel-iommu.h > > > +++ b/include/linux/intel-iommu.h > > > @@ -19,6 +19,7 @@ > > > #include <linux/iommu.h> > > > #include <linux/io-64-nonatomic-lo-hi.h> > > > #include <linux/dmar.h> > > > +#include <linux/ioasid.h> > > > > > > #include <asm/cacheflush.h> > > > #include <asm/iommu.h> > > > @@ -563,6 +564,7 @@ struct intel_iommu { > > > #ifdef CONFIG_INTEL_IOMMU_SVM > > > struct page_req_dsc *prq; > > > unsigned char prq_name[16]; /* Name for PRQ interrupt */ > > > + struct ioasid_allocator_ops pasid_allocator; /* Custom > > > allocator for PASIDs */ > > > #endif > > > struct q_inval *qi; /* Queued invalidation > > > info */ u32 *iommu_state; /* Store iommu states between suspend and > > > resume.*/ > > > -- > > > 2.7.4 > > > > [Jacob Pan]
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