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vfio: ccw: refactor and improve pfn_array_alloc_pin()

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This refactors pfn_array_alloc_pin() and also improves it by adding
defensive code in error handling so that calling pfn_array_unpin_free()
after error return won't lead to problem. This mainly does:
1. Merge pfn_array_pin() into pfn_array_alloc_pin(), since there is no
   other user of pfn_array_pin(). As a result, also remove kernel-doc
   for pfn_array_pin() and add/update kernel-doc for pfn_array_alloc_pin()
   and struct pfn_array.
2. For a vfio_pin_pages() failure, set pa->pa_nr to zero to indicate
   zero pages were pinned.
3. Set pa->pa_iova_pfn to NULL right after it was freed.

Suggested-by: Pierre Morel <pmorel@linux.ibm.com>
Signed-off-by: Dong Jia Shi <bjsdjshi@linux.ibm.com>
Message-Id: <20180523025645.8978-3-bjsdjshi@linux.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
This commit is contained in:
Dong Jia Shi 2018-05-23 04:56:43 +02:00 committed by Cornelia Huck
parent 80c57f7a07
commit 5c1cfb1c39
1 changed files with 38 additions and 48 deletions
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86
drivers/s390/cio/vfio_ccw_cp.c
View file

@ -29,7 +29,7 @@ struct pfn_array {
unsigned long *pa_iova_pfn;
/* Array that receives PFNs of the pages pinned. */
unsigned long *pa_pfn;
/* Number of pages to pin/pinned from @pa_iova. */
/* Number of pages pinned from @pa_iova. */
int pa_nr;
};
@ -50,64 +50,33 @@ struct ccwchain {
};
/*
* pfn_array_pin() - pin user pages in memory
* pfn_array_alloc_pin() - alloc memory for PFNs, then pin user pages in memory
* @pa: pfn_array on which to perform the operation
* @mdev: the mediated device to perform pin/unpin operations
* @iova: target guest physical address
* @len: number of bytes that should be pinned from @iova
*
* Attempt to pin user pages in memory.
* Attempt to allocate memory for PFNs, and pin user pages in memory.
*
* Usage of pfn_array:
* Any field in this structure should be initialized by caller.
* We expect @pa->pa_nr > 0, and its value will be assigned by callee.
* We expect (pa_nr == 0) and (pa_iova_pfn == NULL), any field in
* this structure will be filled in by this function.
*
* Returns:
* Number of pages pinned on success.
* If @pa->pa_nr is 0 or negative, returns 0.
* If @pa->pa_nr is not 0, or @pa->pa_iova_pfn is not NULL initially,
* returns -EINVAL.
* If no pages were pinned, returns -errno.
*/
static int pfn_array_pin(struct pfn_array *pa, struct device *mdev)
{
int i, ret;
if (pa->pa_nr <= 0) {
pa->pa_nr = 0;
return 0;
}
pa->pa_iova_pfn[0] = pa->pa_iova >> PAGE_SHIFT;
for (i = 1; i < pa->pa_nr; i++)
pa->pa_iova_pfn[i] = pa->pa_iova_pfn[i - 1] + 1;
ret = vfio_pin_pages(mdev, pa->pa_iova_pfn, pa->pa_nr,
IOMMU_READ | IOMMU_WRITE, pa->pa_pfn);
if (ret > 0 && ret != pa->pa_nr) {
vfio_unpin_pages(mdev, pa->pa_iova_pfn, ret);
pa->pa_nr = 0;
return 0;
}
return ret;
}
/* Unpin the pages before releasing the memory. */
static void pfn_array_unpin_free(struct pfn_array *pa, struct device *mdev)
{
vfio_unpin_pages(mdev, pa->pa_iova_pfn, pa->pa_nr);
pa->pa_nr = 0;
kfree(pa->pa_iova_pfn);
}
/* Alloc memory for PFNs, then pin pages with them. */
static int pfn_array_alloc_pin(struct pfn_array *pa, struct device *mdev,
u64 iova, unsigned int len)
{
int ret = 0;
int i, ret = 0;
if (!len)
return 0;
if (pa->pa_nr)
if (pa->pa_nr || pa->pa_iova_pfn)
return -EINVAL;
pa->pa_iova = iova;
@ -124,16 +93,37 @@ static int pfn_array_alloc_pin(struct pfn_array *pa, struct device *mdev,
return -ENOMEM;
pa->pa_pfn = pa->pa_iova_pfn + pa->pa_nr;
ret = pfn_array_pin(pa, mdev);
pa->pa_iova_pfn[0] = pa->pa_iova >> PAGE_SHIFT;
for (i = 1; i < pa->pa_nr; i++)
pa->pa_iova_pfn[i] = pa->pa_iova_pfn[i - 1] + 1;
if (ret > 0)
return ret;
else if (!ret)
ret = vfio_pin_pages(mdev, pa->pa_iova_pfn, pa->pa_nr,
IOMMU_READ | IOMMU_WRITE, pa->pa_pfn);
if (ret < 0) {
goto err_out;
} else if (ret > 0 && ret != pa->pa_nr) {
vfio_unpin_pages(mdev, pa->pa_iova_pfn, ret);
ret = -EINVAL;
kfree(pa->pa_iova_pfn);
goto err_out;
}
return ret;
err_out:
pa->pa_nr = 0;
kfree(pa->pa_iova_pfn);
pa->pa_iova_pfn = NULL;
return ret;
}
/* Unpin the pages before releasing the memory. */
static void pfn_array_unpin_free(struct pfn_array *pa, struct device *mdev)
{
vfio_unpin_pages(mdev, pa->pa_iova_pfn, pa->pa_nr);
pa->pa_nr = 0;
kfree(pa->pa_iova_pfn);
}
static int pfn_array_table_init(struct pfn_array_table *pat, int nr)