[PULL 3/7] s390/cio: Split pfn_array_alloc_pin into pieces

Cornelia Huck
2019-06-03T10:50:34Z

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@linux.ibm.com>
Message-Id: <20190514234248.36203-4-farman@linux.ibm.com>
Reviewed-by: Farhan Ali <alifm@linux.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
---
drivers/s390/cio/vfio_ccw_cp.c | 64 ++++++++++++++++++++++++----------
1 file changed, 46 insertions(+), 18 deletions(-)

diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
index 6e48b66ae31a..e33265fb80b0 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 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;
@@ -97,6 +94,22 @@ 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 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);

@@ -112,8 +125,6 @@ static int pfn_array_alloc_pin(struct pfn_array *pa, struct device *mdev,

err_out:
pa->pa_nr = 0;
- kfree(pa->pa_iova_pfn);
- pa->pa_iova_pfn = NULL;

return ret;
}
@@ -121,7 +132,9 @@ static int pfn_array_alloc_pin(struct pfn_array *pa, struct device *mdev,
/* 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);
+ /* Only unpin if any pages were pinned to begin with */
+ if (pa->pa_nr)
+ vfio_unpin_pages(mdev, pa->pa_iova_pfn, pa->pa_nr);
pa->pa_nr = 0;
kfree(pa->pa_iova_pfn);
}
@@ -209,10 +222,16 @@ static long copy_from_iova(struct device *mdev,
int i, ret;
unsigned long l, m;

- ret = pfn_array_alloc_pin(&pa, mdev, iova, n);
- if (ret <= 0)
+ ret = pfn_array_alloc(&pa, iova, n);
+ if (ret < 0)
return ret;

+ ret = pfn_array_pin(&pa, mdev);
+ if (ret < 0) {
+ pfn_array_unpin_free(&pa, mdev);
+ return ret;
+ }
+
l = n;
for (i = 0; i < pa.pa_nr; i++) {
from = pa.pa_pfn[i] << PAGE_SHIFT;
@@ -560,7 +579,11 @@ static int ccwchain_fetch_direct(struct ccwchain *chain,
if (ret)
goto out_init;

- ret = pfn_array_alloc_pin(pat->pat_pa, cp->mdev, ccw->cda, ccw->count);
+ ret = pfn_array_alloc(pat->pat_pa, ccw->cda, ccw->count);
+ if (ret < 0)
+ goto out_unpin;
+
+ ret = pfn_array_pin(pat->pat_pa, cp->mdev);
if (ret < 0)
goto out_unpin;

@@ -590,6 +613,7 @@ static int ccwchain_fetch_idal(struct ccwchain *chain,
{
struct ccw1 *ccw;
struct pfn_array_table *pat;
+ struct pfn_array *pa;
unsigned long *idaws;
u64 idaw_iova;
unsigned int idaw_nr, idaw_len;
@@ -628,9 +652,13 @@ static int ccwchain_fetch_idal(struct ccwchain *chain,

for (i = 0; i < idaw_nr; i++) {
idaw_iova = *(idaws + i);
+ pa = pat->pat_pa + i;
+
+ ret = pfn_array_alloc(pa, idaw_iova, 1);
+ if (ret < 0)
+ goto out_free_idaws;

- ret = pfn_array_alloc_pin(pat->pat_pa + i, cp->mdev,
- idaw_iova, 1);
+ ret = pfn_array_pin(pa, cp->mdev);
if (ret < 0)
goto out_free_idaws;
}
--
2.20.1