Messages in this thread | | | Subject | Re: [PATCH v2 11/12] x86/mmu: Allocate/free PASID | From | Lu Baolu <> | Date | Sat, 13 Jun 2020 21:07:24 +0800 |
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Hi Fenghua,
On 2020/6/13 8:41, Fenghua Yu wrote: > A PASID is allocated for an "mm" the first time any thread attaches > to an SVM capable device. Later device attachments (whether to the same > device or another SVM device) will re-use the same PASID. > > The PASID is freed when the process exits (so no need to keep > reference counts on how many SVM devices are sharing the PASID).
FYI.
Jean-Philippe Brucker has a patch for mm->pasid management in the vendor agnostic manner.
https://www.spinics.net/lists/iommu/msg44459.html
Best regards, baolu
> > Signed-off-by: Fenghua Yu <fenghua.yu@intel.com> > Reviewed-by: Tony Luck <tony.luck@intel.com> > --- > v2: > - Define a helper free_bind() to simplify error exit code in bind_mm() > (Thomas) > - Fix a ret error code in bind_mm() (Thomas) > - Change pasid's type from "int" to "unsigned int" to have consistent > pasid type in iommu (Thomas) > - Simplify alloc_pasid() a bit. > > arch/x86/include/asm/iommu.h | 2 + > arch/x86/include/asm/mmu_context.h | 14 ++++ > drivers/iommu/intel/svm.c | 101 +++++++++++++++++++++++++---- > 3 files changed, 105 insertions(+), 12 deletions(-) > > diff --git a/arch/x86/include/asm/iommu.h b/arch/x86/include/asm/iommu.h > index bf1ed2ddc74b..ed41259fe7ac 100644 > --- a/arch/x86/include/asm/iommu.h > +++ b/arch/x86/include/asm/iommu.h > @@ -26,4 +26,6 @@ arch_rmrr_sanity_check(struct acpi_dmar_reserved_memory *rmrr) > return -EINVAL; > } > > +void __free_pasid(struct mm_struct *mm); > + > #endif /* _ASM_X86_IOMMU_H */ > diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h > index 47562147e70b..f8c91ce8c451 100644 > --- a/arch/x86/include/asm/mmu_context.h > +++ b/arch/x86/include/asm/mmu_context.h > @@ -13,6 +13,7 @@ > #include <asm/tlbflush.h> > #include <asm/paravirt.h> > #include <asm/debugreg.h> > +#include <asm/iommu.h> > > extern atomic64_t last_mm_ctx_id; > > @@ -117,9 +118,22 @@ static inline int init_new_context(struct task_struct *tsk, > init_new_context_ldt(mm); > return 0; > } > + > +static inline void free_pasid(struct mm_struct *mm) > +{ > + if (!IS_ENABLED(CONFIG_INTEL_IOMMU_SVM)) > + return; > + > + if (!cpu_feature_enabled(X86_FEATURE_ENQCMD)) > + return; > + > + __free_pasid(mm); > +} > + > static inline void destroy_context(struct mm_struct *mm) > { > destroy_context_ldt(mm); > + free_pasid(mm); > } > > extern void switch_mm(struct mm_struct *prev, struct mm_struct *next, > diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c > index 4e775e12ae52..27dc866b8461 100644 > --- a/drivers/iommu/intel/svm.c > +++ b/drivers/iommu/intel/svm.c > @@ -425,6 +425,53 @@ int intel_svm_unbind_gpasid(struct device *dev, unsigned int pasid) > return ret; > } > > +static void free_bind(struct intel_svm *svm, struct intel_svm_dev *sdev, > + bool new_pasid) > +{ > + if (new_pasid) > + ioasid_free(svm->pasid); > + kfree(svm); > + kfree(sdev); > +} > + > +/* > + * If this mm already has a PASID, use it. Otherwise allocate a new one. > + * Let the caller know if a new PASID is allocated via 'new_pasid'. > + */ > +static int alloc_pasid(struct intel_svm *svm, struct mm_struct *mm, > + unsigned int pasid_max, bool *new_pasid, > + unsigned int flags) > +{ > + unsigned int pasid; > + > + *new_pasid = false; > + > + /* > + * Reuse the PASID if the mm already has a PASID and not a private > + * PASID is requested. > + */ > + if (mm && mm->pasid && !(flags & SVM_FLAG_PRIVATE_PASID)) { > + /* > + * Once a PASID is allocated for this mm, the PASID > + * stays with the mm until the mm is dropped. Reuse > + * the PASID which has been already allocated for the > + * mm instead of allocating a new one. > + */ > + ioasid_set_data(mm->pasid, svm); > + > + return mm->pasid; > + } > + > + /* Allocate a new pasid. Do not use PASID 0, reserved for init PASID. */ > + pasid = ioasid_alloc(NULL, PASID_MIN, pasid_max - 1, svm); > + if (pasid != INVALID_IOASID) { > + /* A new pasid is allocated. */ > + *new_pasid = true; > + } > + > + return pasid; > +} > + > /* Caller must hold pasid_mutex, mm reference */ > static int > intel_svm_bind_mm(struct device *dev, unsigned int flags, > @@ -518,6 +565,8 @@ intel_svm_bind_mm(struct device *dev, unsigned int flags, > init_rcu_head(&sdev->rcu); > > if (!svm) { > + bool new_pasid; > + > svm = kzalloc(sizeof(*svm), GFP_KERNEL); > if (!svm) { > ret = -ENOMEM; > @@ -529,12 +578,9 @@ intel_svm_bind_mm(struct device *dev, unsigned int flags, > if (pasid_max > intel_pasid_max_id) > pasid_max = intel_pasid_max_id; > > - /* Do not use PASID 0, reserved for RID to PASID */ > - svm->pasid = ioasid_alloc(NULL, PASID_MIN, > - pasid_max - 1, svm); > + svm->pasid = alloc_pasid(svm, mm, pasid_max, &new_pasid, flags); > if (svm->pasid == INVALID_IOASID) { > - kfree(svm); > - kfree(sdev); > + free_bind(svm, sdev, new_pasid); > ret = -ENOSPC; > goto out; > } > @@ -547,9 +593,7 @@ intel_svm_bind_mm(struct device *dev, unsigned int flags, > if (mm) { > ret = mmu_notifier_register(&svm->notifier, mm); > if (ret) { > - ioasid_free(svm->pasid); > - kfree(svm); > - kfree(sdev); > + free_bind(svm, sdev, new_pasid); > goto out; > } > } > @@ -565,12 +609,18 @@ intel_svm_bind_mm(struct device *dev, unsigned int flags, > if (ret) { > if (mm) > mmu_notifier_unregister(&svm->notifier, mm); > - ioasid_free(svm->pasid); > - kfree(svm); > - kfree(sdev); > + free_bind(svm, sdev, new_pasid); > goto out; > } > > + if (mm && new_pasid && !(flags & SVM_FLAG_PRIVATE_PASID)) { > + /* > + * Track the new pasid in the mm. The pasid will be > + * freed at process exit. Don't track requested > + * private PASID in the mm. > + */ > + mm->pasid = svm->pasid; > + } > list_add_tail(&svm->list, &global_svm_list); > } else { > /* > @@ -640,7 +690,8 @@ static int intel_svm_unbind_mm(struct device *dev, unsigned int pasid) > kfree_rcu(sdev, rcu); > > if (list_empty(&svm->devs)) { > - ioasid_free(svm->pasid); > + /* Clear data in the pasid. */ > + ioasid_set_data(pasid, NULL); > if (svm->mm) > mmu_notifier_unregister(&svm->notifier, svm->mm); > list_del(&svm->list); > @@ -1001,3 +1052,29 @@ unsigned int intel_svm_get_pasid(struct iommu_sva *sva) > > return pasid; > } > + > +/* > + * An invalid pasid is either 0 (init PASID value) or bigger than max PASID > + * (PASID_MAX - 1). > + */ > +static bool invalid_pasid(unsigned int pasid) > +{ > + return (pasid == INIT_PASID) || (pasid >= PASID_MAX); > +} > + > +/* On process exit free the PASID (if one was allocated). */ > +void __free_pasid(struct mm_struct *mm) > +{ > + unsigned int pasid = mm->pasid; > + > + /* No need to free invalid pasid. */ > + if (invalid_pasid(pasid)) > + return; > + > + /* > + * Since the pasid is not bound to any svm by now, there is no race > + * here with binding/unbinding and no need to protect the free > + * operation by pasid_mutex. > + */ > + ioasid_free(pasid); > +} >
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