Commit a5deabe0 authored by Andres Lagar-Cavilla's avatar Andres Lagar-Cavilla Committed by Konrad Rzeszutek Wilk
Browse files

Xen: Fix retry calls into PRIVCMD_MMAPBATCH*. 



When a foreign mapper attempts to map guest frames that are paged out,
the mapper receives an ENOENT response and will have to try again
while a helper process pages the target frame back in.

Gating checks on PRIVCMD_MMAPBATCH* ioctl args were preventing retries
of mapping calls.

Permit subsequent calls to update a sub-range of the VMA, iff nothing
is yet mapped in that range.

Since it is now valid to call PRIVCMD_MMAPBATCH* multiple times, only
set vma->vm_private_data if the parameters are valid and (if
necessary) the pages for the auto_translated_physmap case have been
allocated.  This prevents subsequent calls from incorrectly entering
the 'retry' path when there are no pages allocated etc.

Signed-off-by: default avatarAndres Lagar-Cavilla <andres@lagarcavilla.org>
Signed-off-by: default avatarDavid Vrabel <david.vrabel@citrix.com>
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent 669b0ae9

drivers/xen/privcmd.c

+63 −20
Original line number Diff line number Diff line
@@ -43,9 +43,10 @@ MODULE_LICENSE("GPL"); 


#define PRIV_VMA_LOCKED ((void *)1)



#ifndef HAVE_ARCH_PRIVCMD_MMAP

static int privcmd_enforce_singleshot_mapping(struct vm_area_struct *vma);

#endif

static int privcmd_vma_range_is_mapped(

               struct vm_area_struct *vma,

               unsigned long addr,

               unsigned long nr_pages);



static long privcmd_ioctl_hypercall(void __user *udata)

{
@@ -225,9 +226,9 @@ static long privcmd_ioctl_mmap(void __user *udata) 
		vma = find_vma(mm, msg->va);

		rc = -EINVAL;



		if (!vma || (msg->va != vma->vm_start) ||

		    !privcmd_enforce_singleshot_mapping(vma))

		if (!vma || (msg->va != vma->vm_start) || vma->vm_private_data)

			goto out_up;

		vma->vm_private_data = PRIV_VMA_LOCKED;

	}



	state.va = vma->vm_start;
@@ -358,7 +359,7 @@ static int alloc_empty_pages(struct vm_area_struct *vma, int numpgs) 
		kfree(pages);

		return -ENOMEM;

	}

	BUG_ON(vma->vm_private_data != PRIV_VMA_LOCKED);

	BUG_ON(vma->vm_private_data != NULL);

	vma->vm_private_data = pages;



	return 0;
@@ -421,19 +422,43 @@ static long privcmd_ioctl_mmap_batch(void __user *udata, int version) 


	vma = find_vma(mm, m.addr);

	if (!vma ||

	    vma->vm_ops != &privcmd_vm_ops ||

	    (m.addr != vma->vm_start) ||

	    ((m.addr + (nr_pages << PAGE_SHIFT)) != vma->vm_end) ||

	    !privcmd_enforce_singleshot_mapping(vma)) {

		up_write(&mm->mmap_sem);

	    vma->vm_ops != &privcmd_vm_ops) {

		ret = -EINVAL;

		goto out;

		goto out_unlock;

	}



	/*

	 * Caller must either:

	 *

	 * Map the whole VMA range, which will also allocate all the

	 * pages required for the auto_translated_physmap case.

	 *

	 * Or

	 *

	 * Map unmapped holes left from a previous map attempt (e.g.,

	 * because those foreign frames were previously paged out).

	 */

	if (vma->vm_private_data == NULL) {

		if (m.addr != vma->vm_start ||

		    m.addr + (nr_pages << PAGE_SHIFT) != vma->vm_end) {

			ret = -EINVAL;

			goto out_unlock;

		}

		if (xen_feature(XENFEAT_auto_translated_physmap)) {

			ret = alloc_empty_pages(vma, m.num);

		if (ret < 0) {

			up_write(&mm->mmap_sem);

			goto out;

			if (ret < 0)

				goto out_unlock;

		} else

			vma->vm_private_data = PRIV_VMA_LOCKED;

	} else {

		if (m.addr < vma->vm_start ||

		    m.addr + (nr_pages << PAGE_SHIFT) > vma->vm_end) {

			ret = -EINVAL;

			goto out_unlock;

		}

		if (privcmd_vma_range_is_mapped(vma, m.addr, nr_pages)) {

			ret = -EINVAL;

			goto out_unlock;

		}

	}
@@ -466,8 +491,11 @@ static long privcmd_ioctl_mmap_batch(void __user *udata, int version) 


out:

	free_page_list(&pagelist);



	return ret;



out_unlock:

	up_write(&mm->mmap_sem);

	goto out;

}



static long privcmd_ioctl(struct file *file,
@@ -540,9 +568,24 @@ static int privcmd_mmap(struct file *file, struct vm_area_struct *vma) 
	return 0;

}



static int privcmd_enforce_singleshot_mapping(struct vm_area_struct *vma)

/*

 * For MMAPBATCH*. This allows asserting the singleshot mapping

 * on a per pfn/pte basis. Mapping calls that fail with ENOENT

 * can be then retried until success.

 */

static int is_mapped_fn(pte_t *pte, struct page *pmd_page,

	                unsigned long addr, void *data)

{

	return pte_none(*pte) ? 0 : -EBUSY;

}



static int privcmd_vma_range_is_mapped(

	           struct vm_area_struct *vma,

	           unsigned long addr,

	           unsigned long nr_pages)

{

	return !cmpxchg(&vma->vm_private_data, NULL, PRIV_VMA_LOCKED);

	return apply_to_page_range(vma->vm_mm, addr, nr_pages << PAGE_SHIFT,

				   is_mapped_fn, NULL) != 0;

}



const struct file_operations xen_privcmd_fops = {

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