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Date: Mon, 7 Nov 2016 14:03:48 -0700
From: Alex Williamson <alex.williamson@...hat.com>
To: Kirti Wankhede <kwankhede@...dia.com>
Cc: <pbonzini@...hat.com>, <kraxel@...hat.com>, <cjia@...dia.com>,
<qemu-devel@...gnu.org>, <kvm@...r.kernel.org>,
<kevin.tian@...el.com>, <jike.song@...el.com>,
<bjsdjshi@...ux.vnet.ibm.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v11 09/22] vfio iommu type1: Add task structure to
vfio_dma
On Sat, 5 Nov 2016 02:40:43 +0530
Kirti Wankhede <kwankhede@...dia.com> wrote:
> Add task structure to vfio_dma.
> Add address space structure. Each vfio_dma structure points to the address
> space of the task who mapped it.
> List of address spaces is maintained in vfio_iommu structure.
> From DMA_MAP call if address space already exist in address space list,
> vfio_dma points to it. If address space doesn't exist, allocate address
> space, save pointer of mm to it and vfio_dma points to it.
> Two tasks can share same address space and so we need keep address space
> structure different from task in vfio_dma structure. vfio_dma keeps
> pointer to its corresponding address space.
> During DMA_UNMAP, same task who mapped it or other task who shares same
> address space is allowed to unmap, otherwise unmap fails.
> QEMU maps few iova ranges initially, then fork threads and from the child
> thread calls DMA_UNMAP on previously mapped iova. Since child shares same
> address space, DMA_UNMAP is successful.
> This address space structure is used to track pages pinned by external
> user in later changes.
>
> Signed-off-by: Kirti Wankhede <kwankhede@...dia.com>
> Signed-off-by: Neo Jia <cjia@...dia.com>
> Change-Id: I7600f1bea6b384fd589fa72421ccf031bcfd9ac5
> ---
> drivers/vfio/vfio_iommu_type1.c | 182 +++++++++++++++++++++++++++++-----------
> 1 file changed, 134 insertions(+), 48 deletions(-)
>
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 422c8d198abb..8d64528dcc22 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -55,12 +55,20 @@ MODULE_PARM_DESC(disable_hugepages,
>
> struct vfio_iommu {
> struct list_head domain_list;
> + struct list_head addr_space_list;
> struct mutex lock;
> struct rb_root dma_list;
> bool v2;
> bool nesting;
> };
>
> +/* address space */
> +struct vfio_addr_space {
> + struct mm_struct *mm;
> + struct list_head next;
> + atomic_t ref_count;
> +};
> +
> struct vfio_domain {
> struct iommu_domain *domain;
> struct list_head next;
> @@ -75,6 +83,9 @@ struct vfio_dma {
> unsigned long vaddr; /* Process virtual addr */
> size_t size; /* Map size (bytes) */
> int prot; /* IOMMU_READ/WRITE */
> + struct vfio_addr_space *addr_space;
> + struct task_struct *task;
> + bool mlock_cap;
> };
>
> struct vfio_group {
> @@ -130,6 +141,18 @@ static void vfio_unlink_dma(struct vfio_iommu *iommu, struct vfio_dma *old)
> rb_erase(&old->node, &iommu->dma_list);
> }
>
> +static struct vfio_addr_space *vfio_find_addr_space(struct vfio_iommu *iommu,
> + struct mm_struct *mm)
> +{
> + struct vfio_addr_space *as;
> +
> + list_for_each_entry(as, &iommu->addr_space_list, next) {
> + if (as->mm == mm)
> + return as;
> + }
> + return NULL;
> +}
> +
> struct vwork {
> struct mm_struct *mm;
> long npage;
> @@ -273,24 +296,24 @@ static int vaddr_get_pfn(struct mm_struct *mm, unsigned long vaddr,
> * the iommu can only map chunks of consecutive pfns anyway, so get the
> * first page and all consecutive pages with the same locking.
> */
> -static long __vfio_pin_pages_remote(unsigned long vaddr, long npage,
> - int prot, unsigned long *pfn_base)
> +static long __vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,
> + long npage, int prot,
> + unsigned long *pfn_base)
> {
> - unsigned long limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
> - bool lock_cap = capable(CAP_IPC_LOCK);
> + struct task_struct *task = dma->task;
> + unsigned long limit = task_rlimit(task, RLIMIT_MEMLOCK) >> PAGE_SHIFT;
> + bool lock_cap = dma->mlock_cap;
> + struct mm_struct *mm = dma->addr_space->mm;
> long ret, i;
> bool rsvd;
>
> - if (!current->mm)
> - return -ENODEV;
> -
> - ret = vaddr_get_pfn(current->mm, vaddr, prot, pfn_base);
> + ret = vaddr_get_pfn(mm, vaddr, prot, pfn_base);
> if (ret)
> return ret;
>
> rsvd = is_invalid_reserved_pfn(*pfn_base);
>
> - if (!rsvd && !lock_cap && current->mm->locked_vm + 1 > limit) {
> + if (!rsvd && !lock_cap && mm->locked_vm + 1 > limit) {
> put_pfn(*pfn_base, prot);
> pr_warn("%s: RLIMIT_MEMLOCK (%ld) exceeded\n", __func__,
> limit << PAGE_SHIFT);
> @@ -299,7 +322,7 @@ static long __vfio_pin_pages_remote(unsigned long vaddr, long npage,
>
> if (unlikely(disable_hugepages)) {
> if (!rsvd)
> - vfio_lock_acct(current->mm, 1);
> + vfio_lock_acct(mm, 1);
> return 1;
> }
>
> @@ -307,7 +330,7 @@ static long __vfio_pin_pages_remote(unsigned long vaddr, long npage,
> for (i = 1, vaddr += PAGE_SIZE; i < npage; i++, vaddr += PAGE_SIZE) {
> unsigned long pfn = 0;
>
> - ret = vaddr_get_pfn(current->mm, vaddr, prot, &pfn);
> + ret = vaddr_get_pfn(mm, vaddr, prot, &pfn);
> if (ret)
> break;
>
> @@ -318,7 +341,7 @@ static long __vfio_pin_pages_remote(unsigned long vaddr, long npage,
> }
>
> if (!rsvd && !lock_cap &&
> - current->mm->locked_vm + i + 1 > limit) {
> + mm->locked_vm + i + 1 > limit) {
> put_pfn(pfn, prot);
> pr_warn("%s: RLIMIT_MEMLOCK (%ld) exceeded\n",
> __func__, limit << PAGE_SHIFT);
> @@ -327,13 +350,13 @@ static long __vfio_pin_pages_remote(unsigned long vaddr, long npage,
> }
>
> if (!rsvd)
> - vfio_lock_acct(current->mm, i);
> + vfio_lock_acct(mm, i);
>
> return i;
> }
>
> -static long __vfio_unpin_pages_remote(unsigned long pfn, long npage,
> - int prot, bool do_accounting)
> +static long __vfio_unpin_pages_remote(struct vfio_dma *dma, unsigned long pfn,
> + long npage, int prot, bool do_accounting)
> {
> unsigned long unlocked = 0;
> long i;
> @@ -342,7 +365,7 @@ static long __vfio_unpin_pages_remote(unsigned long pfn, long npage,
> unlocked += put_pfn(pfn++, prot);
>
> if (do_accounting)
> - vfio_lock_acct(current->mm, -unlocked);
> + vfio_lock_acct(dma->addr_space->mm, -unlocked);
>
> return unlocked;
> }
> @@ -396,7 +419,7 @@ static void vfio_unmap_unpin(struct vfio_iommu *iommu, struct vfio_dma *dma)
> if (WARN_ON(!unmapped))
> break;
>
> - unlocked += __vfio_unpin_pages_remote(phys >> PAGE_SHIFT,
> + unlocked += __vfio_unpin_pages_remote(dma, phys >> PAGE_SHIFT,
> unmapped >> PAGE_SHIFT,
> dma->prot, false);
> iova += unmapped;
> @@ -404,13 +427,20 @@ static void vfio_unmap_unpin(struct vfio_iommu *iommu, struct vfio_dma *dma)
> cond_resched();
> }
>
> - vfio_lock_acct(current->mm, -unlocked);
> + vfio_lock_acct(dma->addr_space->mm, -unlocked);
> }
>
> static void vfio_remove_dma(struct vfio_iommu *iommu, struct vfio_dma *dma)
> {
> vfio_unmap_unpin(iommu, dma);
> vfio_unlink_dma(iommu, dma);
> +
> + if (atomic_dec_and_test(&dma->addr_space->ref_count)) {
> + mmput(dma->addr_space->mm);
> + put_task_struct(dma->task);
> + list_del(&dma->addr_space->next);
> + kfree(dma->addr_space);
> + }
> kfree(dma);
> }
>
> @@ -506,6 +536,12 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
> while ((dma = vfio_find_dma(iommu, unmap->iova, unmap->size))) {
> if (!iommu->v2 && unmap->iova > dma->iova)
> break;
> + /*
> + * Task with same address space who mapped this iova range is
> + * allowed to unmap the iova range.
> + */
> + if (dma->task->mm != current->mm)
> + break;
> unmapped += dma->size;
> vfio_remove_dma(iommu, dma);
> }
> @@ -572,17 +608,58 @@ unwind:
> return ret;
> }
>
> +static int vfio_pin_map_dma(struct vfio_iommu *iommu, struct vfio_dma *dma,
> + size_t map_size)
> +{
> + dma_addr_t iova = dma->iova;
> + unsigned long vaddr = dma->vaddr;
> + size_t size = map_size;
> + long npage;
> + unsigned long pfn;
> + int ret = 0;
> +
> + while (size) {
> + /* Pin a contiguous chunk of memory */
> + npage = __vfio_pin_pages_remote(dma, vaddr + dma->size,
> + size >> PAGE_SHIFT, dma->prot,
> + &pfn);
> + if (npage <= 0) {
> + WARN_ON(!npage);
> + ret = (int)npage;
> + break;
> + }
> +
> + /* Map it! */
> + ret = vfio_iommu_map(iommu, iova + dma->size, pfn, npage,
> + dma->prot);
> + if (ret) {
> + __vfio_unpin_pages_remote(dma, pfn, npage, dma->prot,
> + true);
> + break;
> + }
> +
> + size -= npage << PAGE_SHIFT;
> + dma->size += npage << PAGE_SHIFT;
> + }
> +
> + if (ret)
> + vfio_remove_dma(iommu, dma);
> +
> + return ret;
> +}
> +
> static int vfio_dma_do_map(struct vfio_iommu *iommu,
> struct vfio_iommu_type1_dma_map *map)
> {
> dma_addr_t iova = map->iova;
> unsigned long vaddr = map->vaddr;
> size_t size = map->size;
> - long npage;
> int ret = 0, prot = 0;
> uint64_t mask;
> struct vfio_dma *dma;
> - unsigned long pfn;
> + struct vfio_addr_space *addr_space;
> + struct mm_struct *mm;
> + bool free_addr_space_on_err = false;
>
> /* Verify that none of our __u64 fields overflow */
> if (map->size != size || map->vaddr != vaddr || map->iova != iova)
> @@ -608,47 +685,56 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
> mutex_lock(&iommu->lock);
>
> if (vfio_find_dma(iommu, iova, size)) {
> - mutex_unlock(&iommu->lock);
> - return -EEXIST;
> + ret = -EEXIST;
> + goto do_map_err;
> + }
> +
> + mm = get_task_mm(current);
> + if (!mm) {
> + ret = -ENODEV;
-EFAULT?
> + goto do_map_err;
> + }
> +
> + addr_space = vfio_find_addr_space(iommu, mm);
> + if (addr_space) {
> + atomic_inc(&addr_space->ref_count);
> + mmput(mm);
> + } else {
> + addr_space = kzalloc(sizeof(*addr_space), GFP_KERNEL);
> + if (!addr_space) {
> + ret = -ENOMEM;
> + goto do_map_err;
> + }
> + addr_space->mm = mm;
> + atomic_set(&addr_space->ref_count, 1);
> + list_add(&addr_space->next, &iommu->addr_space_list);
> + free_addr_space_on_err = true;
> }
>
> dma = kzalloc(sizeof(*dma), GFP_KERNEL);
> if (!dma) {
> - mutex_unlock(&iommu->lock);
> - return -ENOMEM;
> + if (free_addr_space_on_err) {
> + mmput(mm);
> + list_del(&addr_space->next);
> + kfree(addr_space);
> + }
> + ret = -ENOMEM;
> + goto do_map_err;
> }
>
> dma->iova = iova;
> dma->vaddr = vaddr;
> dma->prot = prot;
> + dma->addr_space = addr_space;
> + get_task_struct(current);
> + dma->task = current;
> + dma->mlock_cap = capable(CAP_IPC_LOCK);
How do you reason we can cache this? Does the fact that the process
had this capability at the time that it did a DMA_MAP imply that it
necessarily still has this capability when an external user (vendor
driver) tries to pin pages? I don't see how we can make that
assumption.
>
> /* Insert zero-sized and grow as we map chunks of it */
> vfio_link_dma(iommu, dma);
>
> - while (size) {
> - /* Pin a contiguous chunk of memory */
> - npage = __vfio_pin_pages_remote(vaddr + dma->size,
> - size >> PAGE_SHIFT, prot, &pfn);
> - if (npage <= 0) {
> - WARN_ON(!npage);
> - ret = (int)npage;
> - break;
> - }
> -
> - /* Map it! */
> - ret = vfio_iommu_map(iommu, iova + dma->size, pfn, npage, prot);
> - if (ret) {
> - __vfio_unpin_pages_remote(pfn, npage, prot, true);
> - break;
> - }
> -
> - size -= npage << PAGE_SHIFT;
> - dma->size += npage << PAGE_SHIFT;
> - }
> -
> - if (ret)
> - vfio_remove_dma(iommu, dma);
> -
> + ret = vfio_pin_map_dma(iommu, dma, size);
> +do_map_err:
> mutex_unlock(&iommu->lock);
> return ret;
> }
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