Re: [PATCH v6 05/15] vfio: Add PASID allocation/free support

Auger Eric
2020-08-13T15:07:27Z

Yi,

On 7/28/20 8:27 AM, Liu Yi L wrote:
> Shared Virtual Addressing (a.k.a Shared Virtual Memory) allows sharing
> multiple process virtual address spaces with the device for simplified
> programming model. PASID is used to tag an virtual address space in DMA
> requests and to identify the related translation structure in IOMMU. When
> a PASID-capable device is assigned to a VM, we want the same capability
> of using PASID to tag guest process virtual address spaces to achieve
> virtual SVA (vSVA).
>
> PASID management for guest is vendor specific. Some vendors (e.g. Intel
> VT-d) requires system-wide managed PASIDs across all devices, regardless
> of whether a device is used by host or assigned to guest. Other vendors
> (e.g. ARM SMMU) may allow PASIDs managed per-device thus could be fully
> delegated to the guest for assigned devices.
>
> For system-wide managed PASIDs, this patch introduces a vfio module to
> handle explicit PASID alloc/free requests from guest. Allocated PASIDs
> are associated to a process (or, mm_struct) in IOASID core. A vfio_mm
> object is introduced to track mm_struct. Multiple VFIO containers within
> a process share the same vfio_mm object.
>
> A quota mechanism is provided to prevent malicious user from exhausting
> available PASIDs. Currently the quota is a global parameter applied to
> all VFIO devices. In the future per-device quota might be supported too.
>
> Cc: Kevin Tian <kevin.tian@intel.com>
> CC: Jacob Pan <jacob.jun.pan@linux.intel.com>
> Cc: Eric Auger <eric.auger@redhat.com>
> Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>
> Cc: Joerg Roedel <joro@8bytes.org>
> Cc: Lu Baolu <baolu.lu@linux.intel.com>
> Suggested-by: Alex Williamson <alex.williamson@redhat.com>
> Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
> ---
> v5 -> v6:
> *) address comments from Eric. Add vfio_unlink_pasid() to be consistent
> with vfio_unlink_dma(). Add a comment in vfio_pasid_exit().
>
> v4 -> v5:
> *) address comments from Eric Auger.
> *) address the comments from Alex on the pasid free range support. Added
> per vfio_mm pasid r-b tree.
> https://lore.kernel.org/kvm/20200709082751.320742ab@x1.home/
>
> v3 -> v4:
> *) fix lock leam in vfio_mm_get_from_task()
> *) drop pasid_quota field in struct vfio_mm
> *) vfio_mm_get_from_task() returns ERR_PTR(-ENOTTY) when !CONFIG_VFIO_PASID
>
> v1 -> v2:
> *) added in v2, split from the pasid alloc/free support of v1
> ---
> drivers/vfio/Kconfig | 5 +
> drivers/vfio/Makefile | 1 +
> drivers/vfio/vfio_pasid.c | 248 ++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/vfio.h | 28 ++++++
> 4 files changed, 282 insertions(+)
> create mode 100644 drivers/vfio/vfio_pasid.c
>
> diff --git a/drivers/vfio/Kconfig b/drivers/vfio/Kconfig
> index fd17db9..3d8a108 100644
> --- a/drivers/vfio/Kconfig
> +++ b/drivers/vfio/Kconfig
> @@ -19,6 +19,11 @@ config VFIO_VIRQFD
> depends on VFIO && EVENTFD
> default n
>
> +config VFIO_PASID
> + tristate
> + depends on IOASID && VFIO
> + default n
> +
> menuconfig VFIO
> tristate "VFIO Non-Privileged userspace driver framework"
> depends on IOMMU_API
> diff --git a/drivers/vfio/Makefile b/drivers/vfio/Makefile
> index de67c47..bb836a3 100644
> --- a/drivers/vfio/Makefile
> +++ b/drivers/vfio/Makefile
> @@ -3,6 +3,7 @@ vfio_virqfd-y := virqfd.o
>
> obj-$(CONFIG_VFIO) += vfio.o
> obj-$(CONFIG_VFIO_VIRQFD) += vfio_virqfd.o
> +obj-$(CONFIG_VFIO_PASID) += vfio_pasid.o
> obj-$(CONFIG_VFIO_IOMMU_TYPE1) += vfio_iommu_type1.o
> obj-$(CONFIG_VFIO_IOMMU_SPAPR_TCE) += vfio_iommu_spapr_tce.o
> obj-$(CONFIG_VFIO_SPAPR_EEH) += vfio_spapr_eeh.o
> diff --git a/drivers/vfio/vfio_pasid.c b/drivers/vfio/vfio_pasid.c
> new file mode 100644
> index 0000000..befcf29
> --- /dev/null
> +++ b/drivers/vfio/vfio_pasid.c
> @@ -0,0 +1,248 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2020 Intel Corporation.
> + * Author: Liu Yi L <yi.l.liu@intel.com>
> + *
> + */
> +
> +#include <linux/vfio.h>
> +#include <linux/eventfd.h>
not needed
> +#include <linux/file.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <linux/sched/mm.h>
> +
> +#define DRIVER_VERSION "0.1"
> +#define DRIVER_AUTHOR "Liu Yi L <yi.l.liu@intel.com>"
> +#define DRIVER_DESC "PASID management for VFIO bus drivers"
> +
> +#define VFIO_DEFAULT_PASID_QUOTA 1000
> +static int pasid_quota = VFIO_DEFAULT_PASID_QUOTA;
> +module_param_named(pasid_quota, pasid_quota, uint, 0444);
> +MODULE_PARM_DESC(pasid_quota,
> + "Set the quota for max number of PASIDs that an application is allowed to request (default 1000)");
> +
> +struct vfio_mm_token {
> + unsigned long long val;
> +};
> +
> +struct vfio_mm {
> + struct kref kref;
> + int ioasid_sid;
> + struct mutex pasid_lock;
> + struct rb_root pasid_list;
> + struct list_head next;
> + struct vfio_mm_token token;
> +};
> +
> +static struct mutex vfio_mm_lock;
> +static struct list_head vfio_mm_list;
> +
> +struct vfio_pasid {
> + struct rb_node node;
> + ioasid_t pasid;
> +};
> +
> +static void vfio_remove_all_pasids(struct vfio_mm *vmm);
> +
> +/* called with vfio.vfio_mm_lock held */
> +static void vfio_mm_release(struct kref *kref)
> +{
> + struct vfio_mm *vmm = container_of(kref, struct vfio_mm, kref);
> +
> + list_del(&vmm->next);
> + mutex_unlock(&vfio_mm_lock);
> + vfio_remove_all_pasids(vmm);
> + ioasid_free_set(vmm->ioasid_sid, true);
> + kfree(vmm);
> +}
> +
> +void vfio_mm_put(struct vfio_mm *vmm)
> +{
> + kref_put_mutex(&vmm->kref, vfio_mm_release, &vfio_mm_lock);
> +}
> +
> +static void vfio_mm_get(struct vfio_mm *vmm)
> +{
> + kref_get(&vmm->kref);
> +}
> +
> +struct vfio_mm *vfio_mm_get_from_task(struct task_struct *task)
> +{
> + struct mm_struct *mm = get_task_mm(task);
> + struct vfio_mm *vmm;
> + unsigned long long val = (unsigned long long)mm;
> + int ret;
> +
> + mutex_lock(&vfio_mm_lock);
> + /* Search existing vfio_mm with current mm pointer */
> + list_for_each_entry(vmm, &vfio_mm_list, next) {
> + if (vmm->token.val == val) {
> + vfio_mm_get(vmm);
> + goto out;
> + }
> + }
> +
> + vmm = kzalloc(sizeof(*vmm), GFP_KERNEL);
> + if (!vmm) {
> + vmm = ERR_PTR(-ENOMEM);
> + goto out;
> + }
> +
> + /*
> + * IOASID core provides a 'IOASID set' concept to track all
> + * PASIDs associated with a token. Here we use mm_struct as
> + * the token and create a IOASID set per mm_struct. All the
> + * containers of the process share the same IOASID set.
> + */
> + ret = ioasid_alloc_set((struct ioasid_set *)mm, pasid_quota,
> + &vmm->ioasid_sid);
> + if (ret) {
> + kfree(vmm);
> + vmm = ERR_PTR(ret);
> + goto out;
> + }
> +
> + kref_init(&vmm->kref);
> + vmm->token.val = val;
> + mutex_init(&vmm->pasid_lock);
> + vmm->pasid_list = RB_ROOT;
> +
> + list_add(&vmm->next, &vfio_mm_list);> +out:
> + mutex_unlock(&vfio_mm_lock);
> + mmput(mm);
> + return vmm;
> +}
> +
> +/*
> + * Find PASID within @min and @max
> + */
> +static struct vfio_pasid *vfio_find_pasid(struct vfio_mm *vmm,
> + ioasid_t min, ioasid_t max)
> +{
> + struct rb_node *node = vmm->pasid_list.rb_node;
> +
> + while (node) {
> + struct vfio_pasid *vid = rb_entry(node,
> + struct vfio_pasid, node);
> +
> + if (max < vid->pasid)
> + node = node->rb_left;
> + else if (min > vid->pasid)
> + node = node->rb_right;
> + else
> + return vid;
> + }
> +
> + return NULL;
> +}
> +
> +static void vfio_link_pasid(struct vfio_mm *vmm, struct vfio_pasid *new)
> +{
> + struct rb_node **link = &vmm->pasid_list.rb_node, *parent = NULL;
> + struct vfio_pasid *vid;
> +
> + while (*link) {
> + parent = *link;
> + vid = rb_entry(parent, struct vfio_pasid, node);
> +
> + if (new->pasid <= vid->pasid)
> + link = &(*link)->rb_left;
> + else
> + link = &(*link)->rb_right;
> + }
> +
> + rb_link_node(&new->node, parent, link);
> + rb_insert_color(&new->node, &vmm->pasid_list);
> +}
> +
> +static void vfio_unlink_pasid(struct vfio_mm *vmm, struct vfio_pasid *old)
> +{
> + rb_erase(&old->node, &vmm->pasid_list);
> +}
> +
> +static void vfio_remove_pasid(struct vfio_mm *vmm, struct vfio_pasid *vid)
> +{
> + vfio_unlink_pasid(vmm, vid);
> + ioasid_free(vid->pasid);
> + kfree(vid);
> +}
> +
> +static void vfio_remove_all_pasids(struct vfio_mm *vmm)
> +{
> + struct rb_node *node;
> +
> + mutex_lock(&vmm->pasid_lock);
> + while ((node = rb_first(&vmm->pasid_list)))
> + vfio_remove_pasid(vmm, rb_entry(node, struct vfio_pasid, node));
> + mutex_unlock(&vmm->pasid_lock);
> +}
> +
> +int vfio_pasid_alloc(struct vfio_mm *vmm, int min, int max)
> +{
> + ioasid_t pasid;
> + struct vfio_pasid *vid;
> +
> + pasid = ioasid_alloc(vmm->ioasid_sid, min, max, NULL);
> + if (pasid == INVALID_IOASID)
> + return -ENOSPC;
> +
> + vid = kzalloc(sizeof(*vid), GFP_KERNEL);
> + if (!vid) {
> + ioasid_free(pasid);
> + return -ENOMEM;
> + }
> +
> + vid->pasid = pasid;
> +
> + mutex_lock(&vmm->pasid_lock);
> + vfio_link_pasid(vmm, vid);
> + mutex_unlock(&vmm->pasid_lock);
> +
> + return pasid;
> +}
> +
> +void vfio_pasid_free_range(struct vfio_mm *vmm,
> + ioasid_t min, ioasid_t max)
> +{
> + struct vfio_pasid *vid = NULL;
> +
> + /*
> + * IOASID core will notify PASID users (e.g. IOMMU driver) to
> + * teardown necessary structures depending on the to-be-freed
> + * PASID.
> + */
> + mutex_lock(&vmm->pasid_lock);
> + while ((vid = vfio_find_pasid(vmm, min, max)) != NULL)
> + vfio_remove_pasid(vmm, vid);
> + mutex_unlock(&vmm->pasid_lock);
> +}
> +
> +static int __init vfio_pasid_init(void)
> +{
> + mutex_init(&vfio_mm_lock);
> + INIT_LIST_HEAD(&vfio_mm_list);
> + return 0;
> +}
> +
> +static void __exit vfio_pasid_exit(void)
> +{
> + /*
> + * VFIO_PASID is supposed to be referenced by VFIO_IOMMU_TYPE1
> + * and may be other module. once vfio_pasid_exit() is triggered,
> + * that means its user (e.g. VFIO_IOMMU_TYPE1) has been removed.
> + * All the vfio_mm instances should have been released. If not,
> + * means there is vfio_mm leak, should be a bug of user module.
> + * So just warn here.
> + */
> + WARN_ON(!list_empty(&vfio_mm_list));
> +}
> +
> +module_init(vfio_pasid_init);
> +module_exit(vfio_pasid_exit);
> +
> +MODULE_VERSION(DRIVER_VERSION);
> +MODULE_LICENSE("GPL v2");
> +MODULE_AUTHOR(DRIVER_AUTHOR);
> +MODULE_DESCRIPTION(DRIVER_DESC);
> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> index 38d3c6a..31472a9 100644
> --- a/include/linux/vfio.h
> +++ b/include/linux/vfio.h
> @@ -97,6 +97,34 @@ extern int vfio_register_iommu_driver(const struct vfio_iommu_driver_ops *ops);
> extern void vfio_unregister_iommu_driver(
> const struct vfio_iommu_driver_ops *ops);
>
> +struct vfio_mm;
> +#if IS_ENABLED(CONFIG_VFIO_PASID)
> +extern struct vfio_mm *vfio_mm_get_from_task(struct task_struct *task);
> +extern void vfio_mm_put(struct vfio_mm *vmm);
> +extern int vfio_pasid_alloc(struct vfio_mm *vmm, int min, int max);
> +extern void vfio_pasid_free_range(struct vfio_mm *vmm,
> + ioasid_t min, ioasid_t max);
> +#else
> +static inline struct vfio_mm *vfio_mm_get_from_task(struct task_struct *task)
> +{
> + return ERR_PTR(-ENOTTY);
> +}
> +
> +static inline void vfio_mm_put(struct vfio_mm *vmm)
> +{
> +}
> +
> +static inline int vfio_pasid_alloc(struct vfio_mm *vmm, int min, int max)
> +{
> + return -ENOTTY;
> +}
> +
> +static inline void vfio_pasid_free_range(struct vfio_mm *vmm,
> + ioasid_t min, ioasid_t max)
> +{
> +}
> +#endif /* CONFIG_VFIO_PASID */
> +
> /*
> * External user API
> */
>
Besides looks good to me
Reviewed-by: Eric Auger <eric.auger@redhat.com>

Thanks

Eric