s390/cio: Split pfn_array_alloc_pin into pieces

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>

diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
index 6e48b66ae31a77bbac2c80be084147468a5dfc6f..e33265fb80b005871975a99c3709f379d640c0b7 100644 (file)
--- 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 @@ err_out:
 /* 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;
        }