On 5/8/19 6:43 AM, Cornelia Huck wrote:
On Fri, 3 May 2019 15:49:08 +0200
Eric Farman <farman@xxxxxxxxxxxxx> wrote:
The pfn_array_alloc_pin routine is doing too much. Today, it does the
alloc of the pfn_array struct and its member arrays, builds the iova
address lists out of a contiguous piece of guest memory, and asks vfio
to pin the resulting pages.
Let's effectively revert a significant portion of commit 5c1cfb1c3948
("vfio: ccw: refactor and improve pfn_array_alloc_pin()") such that we
break pfn_array_alloc_pin() into its component pieces, and have one
routine that allocates/populates the pfn_array structs, and another
that actually pins the memory. In the future, we will be able to
handle scenarios where pinning memory isn't actually appropriate.
Signed-off-by: Eric Farman <farman@xxxxxxxxxxxxx>
---
drivers/s390/cio/vfio_ccw_cp.c | 72 +++++++++++++++++++++++++++---------------
1 file changed, 47 insertions(+), 25 deletions(-)
diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
index f86da78eaeaa..b70306c06150 100644
--- a/drivers/s390/cio/vfio_ccw_cp.c
+++ b/drivers/s390/cio/vfio_ccw_cp.c
@@ -50,28 +50,25 @@ struct ccwchain {
};
/*
- * pfn_array_alloc_pin() - alloc memory for PFNs, then pin user pages in memory
+ * pfn_array_alloc() - alloc memory for PFNs
* @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 allocate memory for PFNs, and pin user pages in memory.
+ * Attempt to allocate memory for PFN.
s/PFN/PFNs/
*
* Usage of pfn_array:
* 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 not 0, or @pa->pa_iova_pfn is not NULL initially,
- * returns -EINVAL.
- * If no pages were pinned, returns -errno.
+ * 0 if PFNs are allocated
+ * -EINVAL if pa->pa_nr is not initially zero, or pa->pa_iova_pfn is not NULL
+ * -ENOMEM if alloc failed
*/
-static int pfn_array_alloc_pin(struct pfn_array *pa, struct device *mdev,
- u64 iova, unsigned int len)
+static int pfn_array_alloc(struct pfn_array *pa, u64 iova, unsigned int len)
{
- int i, ret = 0;
+ int i;
if (!len)
return 0;
@@ -97,23 +94,33 @@ static int pfn_array_alloc_pin(struct pfn_array *pa, struct device *mdev,
for (i = 1; i < pa->pa_nr; i++)
pa->pa_iova_pfn[i] = pa->pa_iova_pfn[i - 1] + 1;
+ return 0;
+}
+
+/*
+ * pfn_array_pin() - Pin user pages in memory
+ * @pa: pfn_array on which to perform the operation
+ * @mdev: the mediated device to perform pin operations
+ *
+ * Returns:
+ * Number of pages pinned on success.
+ * If fewer pages than requested were pinned, returns -EINVAL
+ * If no pages were pinned, returns -errno.
I don't really like the 'returns -errno' :) It's actually the return
code of vfio_pin_pages(), and that might include -EINVAL as well.
So, what about mentioning in the function description that
pfn_array_pin() only succeeds if it coult pin all pages, and simply
stating that it returns a negative error value on failure?
Seems reasonable to me... Something like:
* Returns number of pages pinned upon success.
* If the pin request partially succeeds, or fails completely,
* all pages are left unpinned and a negative error value is returned.
+ */
+static int pfn_array_pin(struct pfn_array *pa, struct device *mdev)
+{
+ int ret = 0;
+
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) {
+ if (ret > 0 && ret != pa->pa_nr) {
vfio_unpin_pages(mdev, pa->pa_iova_pfn, ret);
ret = -EINVAL;
- goto err_out;
}
- return ret;
-
-err_out:
- pa->pa_nr = 0;
- kfree(pa->pa_iova_pfn);
- pa->pa_iova_pfn = NULL;
+ if (ret < 0)
+ pa->pa_iova = 0;
return ret;
}
(...)
