From: Lu Baolu <baolu.lu@linux.intel.com>
To: Fenghua Yu <fenghua.yu@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Joerg Roedel <joro@8bytes.org>, Ingo Molnar <mingo@redhat.com>,
Borislav Petkov <bp@alien8.de>,
Peter Zijlstra <peterz@infradead.org>,
H Peter Anvin <hpa@zytor.com>,
David Woodhouse <dwmw2@infradead.org>,
Dave Hansen <dave.hansen@intel.com>,
Tony Luck <tony.luck@intel.com>,
Jean-Philippe Brucker <jean-philippe@linaro.org>,
Christoph Hellwig <hch@infradeed.org>,
Ashok Raj <ashok.raj@intel.com>,
Jacob Jun Pan <jacob.jun.pan@intel.com>,
Dave Jiang <dave.jiang@intel.com>,
Sohil Mehta <sohil.mehta@intel.com>,
Ravi V Shankar <ravi.v.shankar@intel.com>
Cc: iommu@lists.linux-foundation.org, x86 <x86@kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v4 10/12] x86/mmu: Allocate/free PASID
Date: Fri, 26 Jun 2020 09:42:51 +0800 [thread overview]
Message-ID: <bb4fb93d-2b70-a724-5ee1-531353bc8e2d@linux.intel.com> (raw)
In-Reply-To: <1593116242-31507-11-git-send-email-fenghua.yu@intel.com>
Hi Fenghua,
On 2020/6/26 4:17, 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).
For changes in Intel VT-d driver,
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Best regards,
baolu
>
> Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
> Reviewed-by: Tony Luck <tony.luck@intel.com>
> ---
> v4:
> - Change PASID type to u32 (Christoph)
>
> v3:
> - Add sanity checks in alloc_pasid() and _free_pasid() (Baolu)
> - Add a comment that the private PASID feature will be removed completely
> from IOMMU and don't track private PASID in mm (Thomas)
>
> 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 | 128 ++++++++++++++++++++++++++---
> 3 files changed, 132 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 8a0cf2f0dd54..4c788880b037 100644
> --- a/drivers/iommu/intel/svm.c
> +++ b/drivers/iommu/intel/svm.c
> @@ -425,6 +425,69 @@ int intel_svm_unbind_gpasid(struct device *dev, u32 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,
> + u32 pasid_max, bool *new_pasid,
> + unsigned int flags)
> +{
> + u32 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)) {
> + void *p;
> +
> + /*
> + * Since the mm has a PASID already, the PASID should be
> + * bound and unbound to the mm before calling this allocation.
> + * So the PASID must be allocated by bind_mm() previously and
> + * should still exist in ioasid; but its data must be cleared
> + * already by unbind_mm().
> + *
> + * Do a sanity check here to ensure the PASID has the right
> + * status before reusing it.
> + */
> + p = ioasid_find(NULL, mm->pasid, NULL);
> + if (IS_ERR(p) || p)
> + return INVALID_IOASID;
> +
> + /*
> + * Once the PASID is allocated for this mm, it
> + * 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 +581,8 @@ 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 +594,9 @@ 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 +609,7 @@ 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 +625,20 @@ 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.
> + *
> + * The private PASID feature will be removed soon from
> + * IOMMU. Don't track requested private PASID in the mm.
> + */
> + mm->pasid = svm->pasid;
> + }
> list_add_tail(&svm->list, &global_svm_list);
> } else {
> /*
> @@ -640,7 +708,8 @@ static int intel_svm_unbind_mm(struct device *dev, u32 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 +1070,38 @@ u32 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(u32 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)
> +{
> + u32 pasid = mm->pasid;
> + void *p;
> +
> + /* No need to free invalid pasid. */
> + if (invalid_pasid(pasid))
> + return;
> +
> + /* The pasid shouldn't be bound to any mm by now. */
> + p = ioasid_find(NULL, pasid, NULL);
> + if (!IS_ERR_OR_NULL(p)) {
> + pr_err("PASID %d is still in use\n", pasid);
> +
> + return;
> + }
> +
> + /*
> + * Since the pasid is not bound to any svm, 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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next prev parent reply other threads:[~2020-06-26 1:43 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-25 20:17 [PATCH v4 00/12] x86: tag application address space for devices Fenghua Yu
2020-06-25 20:17 ` [PATCH v4 01/12] iommu: Change type of pasid to u32 Fenghua Yu
2020-06-26 1:13 ` Lu Baolu
2020-06-25 20:17 ` [PATCH v4 02/12] iommu/vt-d: Change flags type to unsigned int in binding mm Fenghua Yu
2020-06-26 1:14 ` Lu Baolu
2020-06-25 20:17 ` [PATCH v4 03/12] docs: x86: Add documentation for SVA (Shared Virtual Addressing) Fenghua Yu
2020-06-25 20:17 ` [PATCH v4 04/12] x86/cpufeatures: Enumerate ENQCMD and ENQCMDS instructions Fenghua Yu
2020-06-25 20:17 ` [PATCH v4 05/12] x86/fpu/xstate: Add supervisor PASID state for ENQCMD feature Fenghua Yu
2020-06-25 20:17 ` [PATCH v4 06/12] x86/msr-index: Define IA32_PASID MSR Fenghua Yu
2020-06-25 20:17 ` [PATCH v4 07/12] mm: Define pasid in mm Fenghua Yu
2020-06-25 20:17 ` [PATCH v4 08/12] fork: Clear PASID for new mm Fenghua Yu
2020-06-25 20:17 ` [PATCH v4 09/12] x86/process: Clear PASID state for a newly forked/cloned thread Fenghua Yu
2020-06-25 20:17 ` [PATCH v4 10/12] x86/mmu: Allocate/free PASID Fenghua Yu
2020-06-26 1:42 ` Lu Baolu [this message]
2020-06-25 20:17 ` [PATCH v4 11/12] sched: Define and initialize a flag to identify valid PASID in the task Fenghua Yu
2020-06-25 20:17 ` [PATCH v4 12/12] x86/traps: Fix up invalid PASID Fenghua Yu
2020-06-26 1:46 ` Lu Baolu
2020-06-26 9:44 ` Peter Zijlstra
2020-06-26 18:10 ` Luck, Tony
2020-06-26 18:15 ` Borislav Petkov
2020-06-26 18:23 ` Dave Hansen
2020-06-26 18:35 ` Fenghua Yu
2020-06-26 18:16 ` Fenghua Yu
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