[PATCH v3 0/2] vhost-vdpa mapping error path fixes

[PATCH v3 0/2] vhost-vdpa mapping error path fixes

[Si-Wei Liu]

Commit 4c8cf31885f6 ("vhost: introduce vDPA-based backend")
has following issues in the failure path of IOTLB update:

1) vhost_vdpa_map() does not clean up dangling iotlb entry
   upon mapping failure

2) vhost_vdpa_process_iotlb_update() has leakage of pinned
   pages in case of vhost_vdpa_map() failure

This patchset attempts to address the above issues.

Changes in v3:
- Factor out changes in vhost_vdpa_map() and the fix for
  page pinning leak to separate patches (Jason)

---
Si-Wei Liu (2):
  vhost-vdpa: fix vhost_vdpa_map() on error condition
  vhost-vdpa: fix page pinning leakage in error path

 drivers/vhost/vdpa.c | 122 +++++++++++++++++++++++++++++++--------------------
 1 file changed, 74 insertions(+), 48 deletions(-)

-- 
1.8.3.1

[PATCH v3 1/2] vhost-vdpa: fix vhost_vdpa_map() on error condition

[Si-Wei Liu]

vhost_vdpa_map() should remove the iotlb entry just added
if the corresponding mapping fails to set up properly.

Fixes: 4c8cf31885f6 ("vhost: introduce vDPA-based backend")
Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
---
 drivers/vhost/vdpa.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index 796fe97..0f27919 100644
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -565,6 +565,9 @@ static int vhost_vdpa_map(struct vhost_vdpa *v,
 			      perm_to_iommu_flags(perm));
 	}
 
+	if (r)
+		vhost_iotlb_del_range(dev->iotlb, iova, iova + size - 1);
+
 	return r;
 }
 
-- 
1.8.3.1

[PATCH v3 2/2] vhost-vdpa: fix page pinning leakage in error path

[Si-Wei Liu]

Pinned pages are not properly accounted particularly when
mapping error occurs on IOTLB update. Clean up dangling
pinned pages for the error path. As the inflight pinned
pages, specifically for memory region that strides across
multiple chunks, would need more than one free page for
book keeping and accounting. For simplicity, pin pages
for all memory in the IOVA range in one go rather than
have multiple pin_user_pages calls to make up the entire
region. This way it's easier to track and account the
pages already mapped, particularly for clean-up in the
error path.

Fixes: 4c8cf31885f6 ("vhost: introduce vDPA-based backend")
Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
---
Changes in v3:
- Factor out vhost_vdpa_map() change to a separate patch

Changes in v2:
- Fix incorrect target SHA1 referenced

 drivers/vhost/vdpa.c | 119 ++++++++++++++++++++++++++++++---------------------
 1 file changed, 71 insertions(+), 48 deletions(-)

diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index 0f27919..dad41dae 100644
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -595,21 +595,19 @@ static int vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v,
 	struct vhost_dev *dev = &v->vdev;
 	struct vhost_iotlb *iotlb = dev->iotlb;
 	struct page **page_list;
-	unsigned long list_size = PAGE_SIZE / sizeof(struct page *);
+	struct vm_area_struct **vmas;
 	unsigned int gup_flags = FOLL_LONGTERM;
-	unsigned long npages, cur_base, map_pfn, last_pfn = 0;
-	unsigned long locked, lock_limit, pinned, i;
+	unsigned long map_pfn, last_pfn = 0;
+	unsigned long npages, lock_limit;
+	unsigned long i, nmap = 0;
 	u64 iova = msg->iova;
+	long pinned;
 	int ret = 0;
 
 	if (vhost_iotlb_itree_first(iotlb, msg->iova,
 				    msg->iova + msg->size - 1))
 		return -EEXIST;
 
-	page_list = (struct page **) __get_free_page(GFP_KERNEL);
-	if (!page_list)
-		return -ENOMEM;
-
 	if (msg->perm & VHOST_ACCESS_WO)
 		gup_flags |= FOLL_WRITE;
 
@@ -617,61 +615,86 @@ static int vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v,
 	if (!npages)
 		return -EINVAL;
 
+	page_list = kvmalloc_array(npages, sizeof(struct page *), GFP_KERNEL);
+	vmas = kvmalloc_array(npages, sizeof(struct vm_area_struct *),
+			      GFP_KERNEL);
+	if (!page_list || !vmas) {
+		ret = -ENOMEM;
+		goto free;
+	}
+
 	mmap_read_lock(dev->mm);
 
-	locked = atomic64_add_return(npages, &dev->mm->pinned_vm);
 	lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
-
-	if (locked > lock_limit) {
+	if (npages + atomic64_read(&dev->mm->pinned_vm) > lock_limit) {
 		ret = -ENOMEM;
-		goto out;
+		goto unlock;
 	}
 
-	cur_base = msg->uaddr & PAGE_MASK;
-	iova &= PAGE_MASK;
+	pinned = pin_user_pages(msg->uaddr & PAGE_MASK, npages, gup_flags,
+				page_list, vmas);
+	if (npages != pinned) {
+		if (pinned < 0) {
+			ret = pinned;
+		} else {
+			unpin_user_pages(page_list, pinned);
+			ret = -ENOMEM;
+		}
+		goto unlock;
+	}
 
-	while (npages) {
-		pinned = min_t(unsigned long, npages, list_size);
-		ret = pin_user_pages(cur_base, pinned,
-				     gup_flags, page_list, NULL);
-		if (ret != pinned)
-			goto out;
-
-		if (!last_pfn)
-			map_pfn = page_to_pfn(page_list[0]);
-
-		for (i = 0; i < ret; i++) {
-			unsigned long this_pfn = page_to_pfn(page_list[i]);
-			u64 csize;
-
-			if (last_pfn && (this_pfn != last_pfn + 1)) {
-				/* Pin a contiguous chunk of memory */
-				csize = (last_pfn - map_pfn + 1) << PAGE_SHIFT;
-				if (vhost_vdpa_map(v, iova, csize,
-						   map_pfn << PAGE_SHIFT,
-						   msg->perm))
-					goto out;
-				map_pfn = this_pfn;
-				iova += csize;
+	iova &= PAGE_MASK;
+	map_pfn = page_to_pfn(page_list[0]);
+
+	/* One more iteration to avoid extra vdpa_map() call out of loop. */
+	for (i = 0; i <= npages; i++) {
+		unsigned long this_pfn;
+		u64 csize;
+
+		/* The last chunk may have no valid PFN next to it */
+		this_pfn = i < npages ? page_to_pfn(page_list[i]) : -1UL;
+
+		if (last_pfn && (this_pfn == -1UL ||
+				 this_pfn != last_pfn + 1)) {
+			/* Pin a contiguous chunk of memory */
+			csize = last_pfn - map_pfn + 1;
+			ret = vhost_vdpa_map(v, iova, csize << PAGE_SHIFT,
+					     map_pfn << PAGE_SHIFT,
+					     msg->perm);
+			if (ret) {
+				/*
+				 * Unpin the rest chunks of memory on the
+				 * flight with no corresponding vdpa_map()
+				 * calls having been made yet. On the other
+				 * hand, vdpa_unmap() in the failure path
+				 * is in charge of accounting the number of
+				 * pinned pages for its own.
+				 * This asymmetrical pattern of accounting
+				 * is for efficiency to pin all pages at
+				 * once, while there is no other callsite
+				 * of vdpa_map() than here above.
+				 */
+				unpin_user_pages(&page_list[nmap],
+						 npages - nmap);
+				goto out;
 			}
-
-			last_pfn = this_pfn;
+			atomic64_add(csize, &dev->mm->pinned_vm);
+			nmap += csize;
+			iova += csize << PAGE_SHIFT;
+			map_pfn = this_pfn;
 		}
-
-		cur_base += ret << PAGE_SHIFT;
-		npages -= ret;
+		last_pfn = this_pfn;
 	}
 
-	/* Pin the rest chunk */
-	ret = vhost_vdpa_map(v, iova, (last_pfn - map_pfn + 1) << PAGE_SHIFT,
-			     map_pfn << PAGE_SHIFT, msg->perm);
+	WARN_ON(nmap != npages);
 out:
-	if (ret) {
+	if (ret)
 		vhost_vdpa_unmap(v, msg->iova, msg->size);
-		atomic64_sub(npages, &dev->mm->pinned_vm);
-	}
+unlock:
 	mmap_read_unlock(dev->mm);
-	free_page((unsigned long)page_list);
+free:
+	kvfree(vmas);
+	kvfree(page_list);
 	return ret;
 }
 
-- 
1.8.3.1

Re: [PATCH v3 1/2] vhost-vdpa: fix vhost_vdpa_map() on error condition

[Jason Wang]

On 2020/10/3 下午1:02, Si-Wei Liu wrote:
> vhost_vdpa_map() should remove the iotlb entry just added
> if the corresponding mapping fails to set up properly.
>
> Fixes: 4c8cf31885f6 ("vhost: introduce vDPA-based backend")
> Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
> ---
>   drivers/vhost/vdpa.c | 3 +++
>   1 file changed, 3 insertions(+)
>
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index 796fe97..0f27919 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -565,6 +565,9 @@ static int vhost_vdpa_map(struct vhost_vdpa *v,
>   			      perm_to_iommu_flags(perm));
>   	}
>   
> +	if (r)
> +		vhost_iotlb_del_range(dev->iotlb, iova, iova + size - 1);
> +
>   	return r;
>   }
>   


Acked-by: Jason Wang <jasowang@redhat.com>

Re: [PATCH v3 2/2] vhost-vdpa: fix page pinning leakage in error path

[Jason Wang]

On 2020/10/3 下午1:02, Si-Wei Liu wrote:
> Pinned pages are not properly accounted particularly when
> mapping error occurs on IOTLB update. Clean up dangling
> pinned pages for the error path. As the inflight pinned
> pages, specifically for memory region that strides across
> multiple chunks, would need more than one free page for
> book keeping and accounting. For simplicity, pin pages
> for all memory in the IOVA range in one go rather than
> have multiple pin_user_pages calls to make up the entire
> region. This way it's easier to track and account the
> pages already mapped, particularly for clean-up in the
> error path.
>
> Fixes: 4c8cf31885f6 ("vhost: introduce vDPA-based backend")
> Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
> ---
> Changes in v3:
> - Factor out vhost_vdpa_map() change to a separate patch
>
> Changes in v2:
> - Fix incorrect target SHA1 referenced
>
>   drivers/vhost/vdpa.c | 119 ++++++++++++++++++++++++++++++---------------------
>   1 file changed, 71 insertions(+), 48 deletions(-)
>
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index 0f27919..dad41dae 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -595,21 +595,19 @@ static int vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v,
>   	struct vhost_dev *dev = &v->vdev;
>   	struct vhost_iotlb *iotlb = dev->iotlb;
>   	struct page **page_list;
> -	unsigned long list_size = PAGE_SIZE / sizeof(struct page *);
> +	struct vm_area_struct **vmas;
>   	unsigned int gup_flags = FOLL_LONGTERM;
> -	unsigned long npages, cur_base, map_pfn, last_pfn = 0;
> -	unsigned long locked, lock_limit, pinned, i;
> +	unsigned long map_pfn, last_pfn = 0;
> +	unsigned long npages, lock_limit;
> +	unsigned long i, nmap = 0;
>   	u64 iova = msg->iova;
> +	long pinned;
>   	int ret = 0;
>   
>   	if (vhost_iotlb_itree_first(iotlb, msg->iova,
>   				    msg->iova + msg->size - 1))
>   		return -EEXIST;
>   
> -	page_list = (struct page **) __get_free_page(GFP_KERNEL);
> -	if (!page_list)
> -		return -ENOMEM;
> -
>   	if (msg->perm & VHOST_ACCESS_WO)
>   		gup_flags |= FOLL_WRITE;
>   
> @@ -617,61 +615,86 @@ static int vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v,
>   	if (!npages)
>   		return -EINVAL;
>   
> +	page_list = kvmalloc_array(npages, sizeof(struct page *), GFP_KERNEL);
> +	vmas = kvmalloc_array(npages, sizeof(struct vm_area_struct *),
> +			      GFP_KERNEL);


This will result high order memory allocation which was what the code 
tried to avoid originally.

Using an unlimited size will cause a lot of side effects consider VM or 
userspace may try to pin several TB of memory.


> +	if (!page_list || !vmas) {
> +		ret = -ENOMEM;
> +		goto free;
> +	}


Any reason that you want to use vmas?


> +
>   	mmap_read_lock(dev->mm);
>   
> -	locked = atomic64_add_return(npages, &dev->mm->pinned_vm);
>   	lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
> -
> -	if (locked > lock_limit) {
> +	if (npages + atomic64_read(&dev->mm->pinned_vm) > lock_limit) {
>   		ret = -ENOMEM;
> -		goto out;
> +		goto unlock;
>   	}
>   
> -	cur_base = msg->uaddr & PAGE_MASK;
> -	iova &= PAGE_MASK;
> +	pinned = pin_user_pages(msg->uaddr & PAGE_MASK, npages, gup_flags,
> +				page_list, vmas);
> +	if (npages != pinned) {
> +		if (pinned < 0) {
> +			ret = pinned;
> +		} else {
> +			unpin_user_pages(page_list, pinned);
> +			ret = -ENOMEM;
> +		}
> +		goto unlock;
> +	}
>   
> -	while (npages) {
> -		pinned = min_t(unsigned long, npages, list_size);
> -		ret = pin_user_pages(cur_base, pinned,
> -				     gup_flags, page_list, NULL);
> -		if (ret != pinned)
> -			goto out;
> -
> -		if (!last_pfn)
> -			map_pfn = page_to_pfn(page_list[0]);
> -
> -		for (i = 0; i < ret; i++) {
> -			unsigned long this_pfn = page_to_pfn(page_list[i]);
> -			u64 csize;
> -
> -			if (last_pfn && (this_pfn != last_pfn + 1)) {
> -				/* Pin a contiguous chunk of memory */
> -				csize = (last_pfn - map_pfn + 1) << PAGE_SHIFT;
> -				if (vhost_vdpa_map(v, iova, csize,
> -						   map_pfn << PAGE_SHIFT,
> -						   msg->perm))
> -					goto out;
> -				map_pfn = this_pfn;
> -				iova += csize;
> +	iova &= PAGE_MASK;
> +	map_pfn = page_to_pfn(page_list[0]);
> +
> +	/* One more iteration to avoid extra vdpa_map() call out of loop. */
> +	for (i = 0; i <= npages; i++) {
> +		unsigned long this_pfn;
> +		u64 csize;
> +
> +		/* The last chunk may have no valid PFN next to it */
> +		this_pfn = i < npages ? page_to_pfn(page_list[i]) : -1UL;
> +
> +		if (last_pfn && (this_pfn == -1UL ||
> +				 this_pfn != last_pfn + 1)) {
> +			/* Pin a contiguous chunk of memory */
> +			csize = last_pfn - map_pfn + 1;
> +			ret = vhost_vdpa_map(v, iova, csize << PAGE_SHIFT,
> +					     map_pfn << PAGE_SHIFT,
> +					     msg->perm);
> +			if (ret) {
> +				/*
> +				 * Unpin the rest chunks of memory on the
> +				 * flight with no corresponding vdpa_map()
> +				 * calls having been made yet. On the other
> +				 * hand, vdpa_unmap() in the failure path
> +				 * is in charge of accounting the number of
> +				 * pinned pages for its own.
> +				 * This asymmetrical pattern of accounting
> +				 * is for efficiency to pin all pages at
> +				 * once, while there is no other callsite
> +				 * of vdpa_map() than here above.
> +				 */
> +				unpin_user_pages(&page_list[nmap],
> +						 npages - nmap);
> +				goto out;
>   			}
> -
> -			last_pfn = this_pfn;
> +			atomic64_add(csize, &dev->mm->pinned_vm);
> +			nmap += csize;
> +			iova += csize << PAGE_SHIFT;
> +			map_pfn = this_pfn;
>   		}
> -
> -		cur_base += ret << PAGE_SHIFT;
> -		npages -= ret;
> +		last_pfn = this_pfn;
>   	}


So what I suggest is to fix the pinning leakage first and do the 
possible optimization on top (which is still questionable to me).

Thanks


>   
> -	/* Pin the rest chunk */
> -	ret = vhost_vdpa_map(v, iova, (last_pfn - map_pfn + 1) << PAGE_SHIFT,
> -			     map_pfn << PAGE_SHIFT, msg->perm);
> +	WARN_ON(nmap != npages);
>   out:
> -	if (ret) {
> +	if (ret)
>   		vhost_vdpa_unmap(v, msg->iova, msg->size);
> -		atomic64_sub(npages, &dev->mm->pinned_vm);
> -	}
> +unlock:
>   	mmap_read_unlock(dev->mm);
> -	free_page((unsigned long)page_list);
> +free:
> +	kvfree(vmas);
> +	kvfree(page_list);
>   	return ret;
>   }
>   

Re: [PATCH v3 1/2] vhost-vdpa: fix vhost_vdpa_map() on error condition

[Michael S. Tsirkin]

On Sat, Oct 10, 2020 at 09:48:42AM +0800, Jason Wang wrote:
> 
> On 2020/10/3 下午1:02, Si-Wei Liu wrote:
> > vhost_vdpa_map() should remove the iotlb entry just added
> > if the corresponding mapping fails to set up properly.
> > 
> > Fixes: 4c8cf31885f6 ("vhost: introduce vDPA-based backend")
> > Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
> > ---
> >   drivers/vhost/vdpa.c | 3 +++
> >   1 file changed, 3 insertions(+)
> > 
> > diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> > index 796fe97..0f27919 100644
> > --- a/drivers/vhost/vdpa.c
> > +++ b/drivers/vhost/vdpa.c
> > @@ -565,6 +565,9 @@ static int vhost_vdpa_map(struct vhost_vdpa *v,
> >   			      perm_to_iommu_flags(perm));
> >   	}
> > +	if (r)
> > +		vhost_iotlb_del_range(dev->iotlb, iova, iova + size - 1);
> > +
> >   	return r;
> >   }
> 
> 
> Acked-by: Jason Wang <jasowang@redhat.com>

Linus already merged this, I can't add your ack, sorry!

-- 
MST

Re: [PATCH v3 2/2] vhost-vdpa: fix page pinning leakage in error path

[si-wei liu]

On 10/9/2020 7:27 PM, Jason Wang wrote:
>
> On 2020/10/3 下午1:02, Si-Wei Liu wrote:
>> Pinned pages are not properly accounted particularly when
>> mapping error occurs on IOTLB update. Clean up dangling
>> pinned pages for the error path. As the inflight pinned
>> pages, specifically for memory region that strides across
>> multiple chunks, would need more than one free page for
>> book keeping and accounting. For simplicity, pin pages
>> for all memory in the IOVA range in one go rather than
>> have multiple pin_user_pages calls to make up the entire
>> region. This way it's easier to track and account the
>> pages already mapped, particularly for clean-up in the
>> error path.
>>
>> Fixes: 4c8cf31885f6 ("vhost: introduce vDPA-based backend")
>> Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
>> ---
>> Changes in v3:
>> - Factor out vhost_vdpa_map() change to a separate patch
>>
>> Changes in v2:
>> - Fix incorrect target SHA1 referenced
>>
>>   drivers/vhost/vdpa.c | 119 
>> ++++++++++++++++++++++++++++++---------------------
>>   1 file changed, 71 insertions(+), 48 deletions(-)
>>
>> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
>> index 0f27919..dad41dae 100644
>> --- a/drivers/vhost/vdpa.c
>> +++ b/drivers/vhost/vdpa.c
>> @@ -595,21 +595,19 @@ static int 
>> vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v,
>>       struct vhost_dev *dev = &v->vdev;
>>       struct vhost_iotlb *iotlb = dev->iotlb;
>>       struct page **page_list;
>> -    unsigned long list_size = PAGE_SIZE / sizeof(struct page *);
>> +    struct vm_area_struct **vmas;
>>       unsigned int gup_flags = FOLL_LONGTERM;
>> -    unsigned long npages, cur_base, map_pfn, last_pfn = 0;
>> -    unsigned long locked, lock_limit, pinned, i;
>> +    unsigned long map_pfn, last_pfn = 0;
>> +    unsigned long npages, lock_limit;
>> +    unsigned long i, nmap = 0;
>>       u64 iova = msg->iova;
>> +    long pinned;
>>       int ret = 0;
>>         if (vhost_iotlb_itree_first(iotlb, msg->iova,
>>                       msg->iova + msg->size - 1))
>>           return -EEXIST;
>>   -    page_list = (struct page **) __get_free_page(GFP_KERNEL);
>> -    if (!page_list)
>> -        return -ENOMEM;
>> -
>>       if (msg->perm & VHOST_ACCESS_WO)
>>           gup_flags |= FOLL_WRITE;
>>   @@ -617,61 +615,86 @@ static int 
>> vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v,
>>       if (!npages)
>>           return -EINVAL;
>>   +    page_list = kvmalloc_array(npages, sizeof(struct page *), 
>> GFP_KERNEL);
>> +    vmas = kvmalloc_array(npages, sizeof(struct vm_area_struct *),
>> +                  GFP_KERNEL);
>
>
> This will result high order memory allocation which was what the code 
> tried to avoid originally.
>
> Using an unlimited size will cause a lot of side effects consider VM 
> or userspace may try to pin several TB of memory.
Hmmm, that's a good point. Indeed, if the guest memory demand is huge or 
the host system is running short of free pages, kvmalloc will be 
problematic and less efficient than the __get_free_page implementation.

>
>
>> +    if (!page_list || !vmas) {
>> +        ret = -ENOMEM;
>> +        goto free;
>> +    }
>
>
> Any reason that you want to use vmas?
Without providing custom vmas, it's subject to high order allocation 
failure. While page_list and vmas can now fallback to virtual memory 
allocation if need be.

>
>
>> +
>>       mmap_read_lock(dev->mm);
>>   -    locked = atomic64_add_return(npages, &dev->mm->pinned_vm);
>>       lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
>> -
>> -    if (locked > lock_limit) {
>> +    if (npages + atomic64_read(&dev->mm->pinned_vm) > lock_limit) {
>>           ret = -ENOMEM;
>> -        goto out;
>> +        goto unlock;
>>       }
>>   -    cur_base = msg->uaddr & PAGE_MASK;
>> -    iova &= PAGE_MASK;
>> +    pinned = pin_user_pages(msg->uaddr & PAGE_MASK, npages, gup_flags,
>> +                page_list, vmas);
>> +    if (npages != pinned) {
>> +        if (pinned < 0) {
>> +            ret = pinned;
>> +        } else {
>> +            unpin_user_pages(page_list, pinned);
>> +            ret = -ENOMEM;
>> +        }
>> +        goto unlock;
>> +    }
>>   -    while (npages) {
>> -        pinned = min_t(unsigned long, npages, list_size);
>> -        ret = pin_user_pages(cur_base, pinned,
>> -                     gup_flags, page_list, NULL);
>> -        if (ret != pinned)
>> -            goto out;
>> -
>> -        if (!last_pfn)
>> -            map_pfn = page_to_pfn(page_list[0]);
>> -
>> -        for (i = 0; i < ret; i++) {
>> -            unsigned long this_pfn = page_to_pfn(page_list[i]);
>> -            u64 csize;
>> -
>> -            if (last_pfn && (this_pfn != last_pfn + 1)) {
>> -                /* Pin a contiguous chunk of memory */
>> -                csize = (last_pfn - map_pfn + 1) << PAGE_SHIFT;
>> -                if (vhost_vdpa_map(v, iova, csize,
>> -                           map_pfn << PAGE_SHIFT,
>> -                           msg->perm))
>> -                    goto out;
>> -                map_pfn = this_pfn;
>> -                iova += csize;
>> +    iova &= PAGE_MASK;
>> +    map_pfn = page_to_pfn(page_list[0]);
>> +
>> +    /* One more iteration to avoid extra vdpa_map() call out of 
>> loop. */
>> +    for (i = 0; i <= npages; i++) {
>> +        unsigned long this_pfn;
>> +        u64 csize;
>> +
>> +        /* The last chunk may have no valid PFN next to it */
>> +        this_pfn = i < npages ? page_to_pfn(page_list[i]) : -1UL;
>> +
>> +        if (last_pfn && (this_pfn == -1UL ||
>> +                 this_pfn != last_pfn + 1)) {
>> +            /* Pin a contiguous chunk of memory */
>> +            csize = last_pfn - map_pfn + 1;
>> +            ret = vhost_vdpa_map(v, iova, csize << PAGE_SHIFT,
>> +                         map_pfn << PAGE_SHIFT,
>> +                         msg->perm);
>> +            if (ret) {
>> +                /*
>> +                 * Unpin the rest chunks of memory on the
>> +                 * flight with no corresponding vdpa_map()
>> +                 * calls having been made yet. On the other
>> +                 * hand, vdpa_unmap() in the failure path
>> +                 * is in charge of accounting the number of
>> +                 * pinned pages for its own.
>> +                 * This asymmetrical pattern of accounting
>> +                 * is for efficiency to pin all pages at
>> +                 * once, while there is no other callsite
>> +                 * of vdpa_map() than here above.
>> +                 */
>> +                unpin_user_pages(&page_list[nmap],
>> +                         npages - nmap);
>> +                goto out;
>>               }
>> -
>> -            last_pfn = this_pfn;
>> +            atomic64_add(csize, &dev->mm->pinned_vm);
>> +            nmap += csize;
>> +            iova += csize << PAGE_SHIFT;
>> +            map_pfn = this_pfn;
>>           }
>> -
>> -        cur_base += ret << PAGE_SHIFT;
>> -        npages -= ret;
>> +        last_pfn = this_pfn;
>>       }
>
>
> So what I suggest is to fix the pinning leakage first and do the 
> possible optimization on top (which is still questionable to me).
OK. Unfortunately, this was picked and got merged in upstream. So I will 
post a follow up patch set to 1) revert the commit to the original 
__get_free_page() implementation, and 2) fix the accounting and leakage 
on top. Will it be fine?


-Siwei
>
> Thanks
>
>
>>   -    /* Pin the rest chunk */
>> -    ret = vhost_vdpa_map(v, iova, (last_pfn - map_pfn + 1) << 
>> PAGE_SHIFT,
>> -                 map_pfn << PAGE_SHIFT, msg->perm);
>> +    WARN_ON(nmap != npages);
>>   out:
>> -    if (ret) {
>> +    if (ret)
>>           vhost_vdpa_unmap(v, msg->iova, msg->size);
>> -        atomic64_sub(npages, &dev->mm->pinned_vm);
>> -    }
>> +unlock:
>>       mmap_read_unlock(dev->mm);
>> -    free_page((unsigned long)page_list);
>> +free:
>> +    kvfree(vmas);
>> +    kvfree(page_list);
>>       return ret;
>>   }
>

Re: [PATCH v3 2/2] vhost-vdpa: fix page pinning leakage in error path

[Michael S. Tsirkin]

On Tue, Oct 13, 2020 at 04:42:59PM -0700, si-wei liu wrote:
> 
> On 10/9/2020 7:27 PM, Jason Wang wrote:
> > 
> > On 2020/10/3 下午1:02, Si-Wei Liu wrote:
> > > Pinned pages are not properly accounted particularly when
> > > mapping error occurs on IOTLB update. Clean up dangling
> > > pinned pages for the error path. As the inflight pinned
> > > pages, specifically for memory region that strides across
> > > multiple chunks, would need more than one free page for
> > > book keeping and accounting. For simplicity, pin pages
> > > for all memory in the IOVA range in one go rather than
> > > have multiple pin_user_pages calls to make up the entire
> > > region. This way it's easier to track and account the
> > > pages already mapped, particularly for clean-up in the
> > > error path.
> > > 
> > > Fixes: 4c8cf31885f6 ("vhost: introduce vDPA-based backend")
> > > Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
> > > ---
> > > Changes in v3:
> > > - Factor out vhost_vdpa_map() change to a separate patch
> > > 
> > > Changes in v2:
> > > - Fix incorrect target SHA1 referenced
> > > 
> > >   drivers/vhost/vdpa.c | 119
> > > ++++++++++++++++++++++++++++++---------------------
> > >   1 file changed, 71 insertions(+), 48 deletions(-)
> > > 
> > > diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> > > index 0f27919..dad41dae 100644
> > > --- a/drivers/vhost/vdpa.c
> > > +++ b/drivers/vhost/vdpa.c
> > > @@ -595,21 +595,19 @@ static int
> > > vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v,
> > >       struct vhost_dev *dev = &v->vdev;
> > >       struct vhost_iotlb *iotlb = dev->iotlb;
> > >       struct page **page_list;
> > > -    unsigned long list_size = PAGE_SIZE / sizeof(struct page *);
> > > +    struct vm_area_struct **vmas;
> > >       unsigned int gup_flags = FOLL_LONGTERM;
> > > -    unsigned long npages, cur_base, map_pfn, last_pfn = 0;
> > > -    unsigned long locked, lock_limit, pinned, i;
> > > +    unsigned long map_pfn, last_pfn = 0;
> > > +    unsigned long npages, lock_limit;
> > > +    unsigned long i, nmap = 0;
> > >       u64 iova = msg->iova;
> > > +    long pinned;
> > >       int ret = 0;
> > >         if (vhost_iotlb_itree_first(iotlb, msg->iova,
> > >                       msg->iova + msg->size - 1))
> > >           return -EEXIST;
> > >   -    page_list = (struct page **) __get_free_page(GFP_KERNEL);
> > > -    if (!page_list)
> > > -        return -ENOMEM;
> > > -
> > >       if (msg->perm & VHOST_ACCESS_WO)
> > >           gup_flags |= FOLL_WRITE;
> > >   @@ -617,61 +615,86 @@ static int
> > > vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v,
> > >       if (!npages)
> > >           return -EINVAL;
> > >   +    page_list = kvmalloc_array(npages, sizeof(struct page *),
> > > GFP_KERNEL);
> > > +    vmas = kvmalloc_array(npages, sizeof(struct vm_area_struct *),
> > > +                  GFP_KERNEL);
> > 
> > 
> > This will result high order memory allocation which was what the code
> > tried to avoid originally.
> > 
> > Using an unlimited size will cause a lot of side effects consider VM or
> > userspace may try to pin several TB of memory.
> Hmmm, that's a good point. Indeed, if the guest memory demand is huge or the
> host system is running short of free pages, kvmalloc will be problematic and
> less efficient than the __get_free_page implementation.

OK so ... Jason, what's the plan?

How about you send a patchset with
1. revert this change
2. fix error handling leak


> > 
> > 
> > > +    if (!page_list || !vmas) {
> > > +        ret = -ENOMEM;
> > > +        goto free;
> > > +    }
> > 
> > 
> > Any reason that you want to use vmas?
> Without providing custom vmas, it's subject to high order allocation
> failure. While page_list and vmas can now fallback to virtual memory
> allocation if need be.
> 
> > 
> > 
> > > +
> > >       mmap_read_lock(dev->mm);
> > >   -    locked = atomic64_add_return(npages, &dev->mm->pinned_vm);
> > >       lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
> > > -
> > > -    if (locked > lock_limit) {
> > > +    if (npages + atomic64_read(&dev->mm->pinned_vm) > lock_limit) {
> > >           ret = -ENOMEM;
> > > -        goto out;
> > > +        goto unlock;
> > >       }
> > >   -    cur_base = msg->uaddr & PAGE_MASK;
> > > -    iova &= PAGE_MASK;
> > > +    pinned = pin_user_pages(msg->uaddr & PAGE_MASK, npages, gup_flags,
> > > +                page_list, vmas);
> > > +    if (npages != pinned) {
> > > +        if (pinned < 0) {
> > > +            ret = pinned;
> > > +        } else {
> > > +            unpin_user_pages(page_list, pinned);
> > > +            ret = -ENOMEM;
> > > +        }
> > > +        goto unlock;
> > > +    }
> > >   -    while (npages) {
> > > -        pinned = min_t(unsigned long, npages, list_size);
> > > -        ret = pin_user_pages(cur_base, pinned,
> > > -                     gup_flags, page_list, NULL);
> > > -        if (ret != pinned)
> > > -            goto out;
> > > -
> > > -        if (!last_pfn)
> > > -            map_pfn = page_to_pfn(page_list[0]);
> > > -
> > > -        for (i = 0; i < ret; i++) {
> > > -            unsigned long this_pfn = page_to_pfn(page_list[i]);
> > > -            u64 csize;
> > > -
> > > -            if (last_pfn && (this_pfn != last_pfn + 1)) {
> > > -                /* Pin a contiguous chunk of memory */
> > > -                csize = (last_pfn - map_pfn + 1) << PAGE_SHIFT;
> > > -                if (vhost_vdpa_map(v, iova, csize,
> > > -                           map_pfn << PAGE_SHIFT,
> > > -                           msg->perm))
> > > -                    goto out;
> > > -                map_pfn = this_pfn;
> > > -                iova += csize;
> > > +    iova &= PAGE_MASK;
> > > +    map_pfn = page_to_pfn(page_list[0]);
> > > +
> > > +    /* One more iteration to avoid extra vdpa_map() call out of
> > > loop. */
> > > +    for (i = 0; i <= npages; i++) {
> > > +        unsigned long this_pfn;
> > > +        u64 csize;
> > > +
> > > +        /* The last chunk may have no valid PFN next to it */
> > > +        this_pfn = i < npages ? page_to_pfn(page_list[i]) : -1UL;
> > > +
> > > +        if (last_pfn && (this_pfn == -1UL ||
> > > +                 this_pfn != last_pfn + 1)) {
> > > +            /* Pin a contiguous chunk of memory */
> > > +            csize = last_pfn - map_pfn + 1;
> > > +            ret = vhost_vdpa_map(v, iova, csize << PAGE_SHIFT,
> > > +                         map_pfn << PAGE_SHIFT,
> > > +                         msg->perm);
> > > +            if (ret) {
> > > +                /*
> > > +                 * Unpin the rest chunks of memory on the
> > > +                 * flight with no corresponding vdpa_map()
> > > +                 * calls having been made yet. On the other
> > > +                 * hand, vdpa_unmap() in the failure path
> > > +                 * is in charge of accounting the number of
> > > +                 * pinned pages for its own.
> > > +                 * This asymmetrical pattern of accounting
> > > +                 * is for efficiency to pin all pages at
> > > +                 * once, while there is no other callsite
> > > +                 * of vdpa_map() than here above.
> > > +                 */
> > > +                unpin_user_pages(&page_list[nmap],
> > > +                         npages - nmap);
> > > +                goto out;
> > >               }
> > > -
> > > -            last_pfn = this_pfn;
> > > +            atomic64_add(csize, &dev->mm->pinned_vm);
> > > +            nmap += csize;
> > > +            iova += csize << PAGE_SHIFT;
> > > +            map_pfn = this_pfn;
> > >           }
> > > -
> > > -        cur_base += ret << PAGE_SHIFT;
> > > -        npages -= ret;
> > > +        last_pfn = this_pfn;
> > >       }
> > 
> > 
> > So what I suggest is to fix the pinning leakage first and do the
> > possible optimization on top (which is still questionable to me).
> OK. Unfortunately, this was picked and got merged in upstream. So I will
> post a follow up patch set to 1) revert the commit to the original
> __get_free_page() implementation, and 2) fix the accounting and leakage on
> top. Will it be fine?
> 
> 
> -Siwei
> > 
> > Thanks
> > 
> > 
> > >   -    /* Pin the rest chunk */
> > > -    ret = vhost_vdpa_map(v, iova, (last_pfn - map_pfn + 1) <<
> > > PAGE_SHIFT,
> > > -                 map_pfn << PAGE_SHIFT, msg->perm);
> > > +    WARN_ON(nmap != npages);
> > >   out:
> > > -    if (ret) {
> > > +    if (ret)
> > >           vhost_vdpa_unmap(v, msg->iova, msg->size);
> > > -        atomic64_sub(npages, &dev->mm->pinned_vm);
> > > -    }
> > > +unlock:
> > >       mmap_read_unlock(dev->mm);
> > > -    free_page((unsigned long)page_list);
> > > +free:
> > > +    kvfree(vmas);
> > > +    kvfree(page_list);
> > >       return ret;
> > >   }
> > 

Re: [PATCH v3 2/2] vhost-vdpa: fix page pinning leakage in error path

[Jason Wang]

On 2020/10/14 下午2:52, Michael S. Tsirkin wrote:
> On Tue, Oct 13, 2020 at 04:42:59PM -0700, si-wei liu wrote:
>> On 10/9/2020 7:27 PM, Jason Wang wrote:
>>> On 2020/10/3 下午1:02, Si-Wei Liu wrote:
>>>> Pinned pages are not properly accounted particularly when
>>>> mapping error occurs on IOTLB update. Clean up dangling
>>>> pinned pages for the error path. As the inflight pinned
>>>> pages, specifically for memory region that strides across
>>>> multiple chunks, would need more than one free page for
>>>> book keeping and accounting. For simplicity, pin pages
>>>> for all memory in the IOVA range in one go rather than
>>>> have multiple pin_user_pages calls to make up the entire
>>>> region. This way it's easier to track and account the
>>>> pages already mapped, particularly for clean-up in the
>>>> error path.
>>>>
>>>> Fixes: 4c8cf31885f6 ("vhost: introduce vDPA-based backend")
>>>> Signed-off-by: Si-Wei Liu<si-wei.liu@oracle.com>
>>>> ---
>>>> Changes in v3:
>>>> - Factor out vhost_vdpa_map() change to a separate patch
>>>>
>>>> Changes in v2:
>>>> - Fix incorrect target SHA1 referenced
>>>>
>>>>    drivers/vhost/vdpa.c | 119
>>>> ++++++++++++++++++++++++++++++---------------------
>>>>    1 file changed, 71 insertions(+), 48 deletions(-)
>>>>
>>>> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
>>>> index 0f27919..dad41dae 100644
>>>> --- a/drivers/vhost/vdpa.c
>>>> +++ b/drivers/vhost/vdpa.c
>>>> @@ -595,21 +595,19 @@ static int
>>>> vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v,
>>>>        struct vhost_dev *dev = &v->vdev;
>>>>        struct vhost_iotlb *iotlb = dev->iotlb;
>>>>        struct page **page_list;
>>>> -    unsigned long list_size = PAGE_SIZE / sizeof(struct page *);
>>>> +    struct vm_area_struct **vmas;
>>>>        unsigned int gup_flags = FOLL_LONGTERM;
>>>> -    unsigned long npages, cur_base, map_pfn, last_pfn = 0;
>>>> -    unsigned long locked, lock_limit, pinned, i;
>>>> +    unsigned long map_pfn, last_pfn = 0;
>>>> +    unsigned long npages, lock_limit;
>>>> +    unsigned long i, nmap = 0;
>>>>        u64 iova = msg->iova;
>>>> +    long pinned;
>>>>        int ret = 0;
>>>>          if (vhost_iotlb_itree_first(iotlb, msg->iova,
>>>>                        msg->iova + msg->size - 1))
>>>>            return -EEXIST;
>>>>    -    page_list = (struct page **) __get_free_page(GFP_KERNEL);
>>>> -    if (!page_list)
>>>> -        return -ENOMEM;
>>>> -
>>>>        if (msg->perm & VHOST_ACCESS_WO)
>>>>            gup_flags |= FOLL_WRITE;
>>>>    @@ -617,61 +615,86 @@ static int
>>>> vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v,
>>>>        if (!npages)
>>>>            return -EINVAL;
>>>>    +    page_list = kvmalloc_array(npages, sizeof(struct page *),
>>>> GFP_KERNEL);
>>>> +    vmas = kvmalloc_array(npages, sizeof(struct vm_area_struct *),
>>>> +                  GFP_KERNEL);
>>> This will result high order memory allocation which was what the code
>>> tried to avoid originally.
>>>
>>> Using an unlimited size will cause a lot of side effects consider VM or
>>> userspace may try to pin several TB of memory.
>> Hmmm, that's a good point. Indeed, if the guest memory demand is huge or the
>> host system is running short of free pages, kvmalloc will be problematic and
>> less efficient than the __get_free_page implementation.
> OK so ... Jason, what's the plan?
>
> How about you send a patchset with
> 1. revert this change
> 2. fix error handling leak


Work for me, but it looks like siwei want to do this.

So it's better for to send the patchset.

Thanks


>
>

Re: [PATCH v3 2/2] vhost-vdpa: fix page pinning leakage in error path

[Jason Wang]

On 2020/10/14 上午7:42, si-wei liu wrote:
>>
>>
>> So what I suggest is to fix the pinning leakage first and do the 
>> possible optimization on top (which is still questionable to me).
> OK. Unfortunately, this was picked and got merged in upstream. So I 
> will post a follow up patch set to 1) revert the commit to the 
> original __get_free_page() implementation, and 2) fix the accounting 
> and leakage on top. Will it be fine?


Fine.

Thanks

Re: [PATCH v3 2/2] vhost-vdpa: fix page pinning leakage in error path

[Michael S. Tsirkin]

On Thu, Oct 15, 2020 at 02:15:32PM +0800, Jason Wang wrote:
> 
> On 2020/10/14 上午7:42, si-wei liu wrote:
> > > 
> > > 
> > > So what I suggest is to fix the pinning leakage first and do the
> > > possible optimization on top (which is still questionable to me).
> > OK. Unfortunately, this was picked and got merged in upstream. So I will
> > post a follow up patch set to 1) revert the commit to the original
> > __get_free_page() implementation, and 2) fix the accounting and leakage
> > on top. Will it be fine?
> 
> 
> Fine.
> 
> Thanks

Fine by me too.

Re: [PATCH v3 2/2] vhost-vdpa: fix page pinning leakage in error path

[si-wei liu]

On 10/15/2020 6:11 AM, Michael S. Tsirkin wrote:
> On Thu, Oct 15, 2020 at 02:15:32PM +0800, Jason Wang wrote:
>> On 2020/10/14 上午7:42, si-wei liu wrote:
>>>>
>>>> So what I suggest is to fix the pinning leakage first and do the
>>>> possible optimization on top (which is still questionable to me).
>>> OK. Unfortunately, this was picked and got merged in upstream. So I will
>>> post a follow up patch set to 1) revert the commit to the original
>>> __get_free_page() implementation, and 2) fix the accounting and leakage
>>> on top. Will it be fine?
>>
>> Fine.
>>
>> Thanks
> Fine by me too.
>
Thanks, Michael & Jason. I will post the fix shortly. Stay tuned.

-Siwei

Re: [PATCH v3 2/2] vhost-vdpa: fix page pinning leakage in error path

[Michael S. Tsirkin]

On Thu, Oct 15, 2020 at 01:17:14PM -0700, si-wei liu wrote:
> 
> On 10/15/2020 6:11 AM, Michael S. Tsirkin wrote:
> > On Thu, Oct 15, 2020 at 02:15:32PM +0800, Jason Wang wrote:
> > > On 2020/10/14 上午7:42, si-wei liu wrote:
> > > > > 
> > > > > So what I suggest is to fix the pinning leakage first and do the
> > > > > possible optimization on top (which is still questionable to me).
> > > > OK. Unfortunately, this was picked and got merged in upstream. So I will
> > > > post a follow up patch set to 1) revert the commit to the original
> > > > __get_free_page() implementation, and 2) fix the accounting and leakage
> > > > on top. Will it be fine?
> > > 
> > > Fine.
> > > 
> > > Thanks
> > Fine by me too.
> > 
> Thanks, Michael & Jason. I will post the fix shortly. Stay tuned.
> 
> -Siwei

did I miss the patch?

Re: [PATCH v3 2/2] vhost-vdpa: fix page pinning leakage in error path

[si-wei liu]

On 10/29/2020 2:53 PM, Michael S. Tsirkin wrote:
> On Thu, Oct 15, 2020 at 01:17:14PM -0700, si-wei liu wrote:
>> On 10/15/2020 6:11 AM, Michael S. Tsirkin wrote:
>>> On Thu, Oct 15, 2020 at 02:15:32PM +0800, Jason Wang wrote:
>>>> On 2020/10/14 上午7:42, si-wei liu wrote:
>>>>>> So what I suggest is to fix the pinning leakage first and do the
>>>>>> possible optimization on top (which is still questionable to me).
>>>>> OK. Unfortunately, this was picked and got merged in upstream. So I will
>>>>> post a follow up patch set to 1) revert the commit to the original
>>>>> __get_free_page() implementation, and 2) fix the accounting and leakage
>>>>> on top. Will it be fine?
>>>> Fine.
>>>>
>>>> Thanks
>>> Fine by me too.
>>>
>> Thanks, Michael & Jason. I will post the fix shortly. Stay tuned.
>>
>> -Siwei
> did I miss the patch?
>
You didn't, sorry. I was looking into a way to speed up the boot time 
for large memory guest by multi-threading the page pinning process, and 
it turns out I need more time on that. Will post the fix I have now 
soon, hopefully tomorrow.

-Siwei

Re: [PATCH v3 2/2] vhost-vdpa: fix page pinning leakage in error path

[si-wei liu]

On 10/29/2020 2:53 PM, Michael S. Tsirkin wrote:
> On Thu, Oct 15, 2020 at 01:17:14PM -0700, si-wei liu wrote:
>> On 10/15/2020 6:11 AM, Michael S. Tsirkin wrote:
>>> On Thu, Oct 15, 2020 at 02:15:32PM +0800, Jason Wang wrote:
>>>> On 2020/10/14 上午7:42, si-wei liu wrote:
>>>>>> So what I suggest is to fix the pinning leakage first and do the
>>>>>> possible optimization on top (which is still questionable to me).
>>>>> OK. Unfortunately, this was picked and got merged in upstream. So I will
>>>>> post a follow up patch set to 1) revert the commit to the original
>>>>> __get_free_page() implementation, and 2) fix the accounting and leakage
>>>>> on top. Will it be fine?
>>>> Fine.
>>>>
>>>> Thanks
>>> Fine by me too.
>>>
>> Thanks, Michael & Jason. I will post the fix shortly. Stay tuned.
>>
>> -Siwei
> did I miss the patch?
>
The patch had been posted last Friday. See this thread:

https://lore.kernel.org/virtualization/1604043944-4897-2-git-send-email-si-wei.liu@oracle.com/

-Siwei