vfio-ccw: Move guest_cp storage into common struct

Rather than allocating/freeing a piece of memory every time
we try to figure out how long a CCW chain is, let's use a piece
of memory allocated for each device.

The io_mutex added with commit 4f76617378ee9 ("vfio-ccw: protect
the I/O region") is held for the duration of the VFIO_CCW_EVENT_IO_REQ
event that accesses/uses this space, so there should be no race
concerns with another CPU attempting an (unexpected) SSCH for the
same device.

Suggested-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Eric Farman <farman@linux.ibm.com>
Message-Id: <20190618202352.39702-2-farman@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.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 90d86e1354c1a47a27e789181d3702bd6270f020..f358502376be2e6fd1e825e5833706cc2a2703e9 100644 (file)
--- a/drivers/s390/cio/vfio_ccw_cp.c
+++ b/drivers/s390/cio/vfio_ccw_cp.c
@@ -16,12 +16,6 @@
 
 #include "vfio_ccw_cp.h"
 
-/*
- * Max length for ccw chain.
- * XXX: Limit to 256, need to check more?
- */
-#define CCWCHAIN_LEN_MAX       256
-
 struct pfn_array {
        /* Starting guest physical I/O address. */
        unsigned long           pa_iova;
@@ -386,7 +380,7 @@ static void ccwchain_cda_free(struct ccwchain *chain, int idx)
  */
 static int ccwchain_calc_length(u64 iova, struct channel_program *cp)
 {
-       struct ccw1 *ccw, *p;
+       struct ccw1 *ccw = cp->guest_cp;
        int cnt;
 
        /*
@@ -394,15 +388,9 @@ static int ccwchain_calc_length(u64 iova, struct channel_program *cp)
         * Currently the chain length is limited to CCWCHAIN_LEN_MAX (256).
         * So copying 2K is enough (safe).
         */
-       p = ccw = kcalloc(CCWCHAIN_LEN_MAX, sizeof(*ccw), GFP_KERNEL);
-       if (!ccw)
-               return -ENOMEM;
-
        cnt = copy_ccw_from_iova(cp, ccw, iova, CCWCHAIN_LEN_MAX);
-       if (cnt) {
-               kfree(ccw);
+       if (cnt)
                return cnt;
-       }
 
        cnt = 0;
        do {
@@ -413,10 +401,8 @@ static int ccwchain_calc_length(u64 iova, struct channel_program *cp)
                 * orb specified one of the unsupported formats, we defer
                 * checking for IDAWs in unsupported formats to here.
                 */
-               if ((!cp->orb.cmd.c64 || cp->orb.cmd.i2k) && ccw_is_idal(ccw)) {
-                       kfree(p);
+               if ((!cp->orb.cmd.c64 || cp->orb.cmd.i2k) && ccw_is_idal(ccw))
                        return -EOPNOTSUPP;
-               }
 
                /*
                 * We want to keep counting if the current CCW has the
@@ -435,7 +421,6 @@ static int ccwchain_calc_length(u64 iova, struct channel_program *cp)
        if (cnt == CCWCHAIN_LEN_MAX + 1)
                cnt = -EINVAL;
 
-       kfree(p);
        return cnt;
 }
 
@@ -461,7 +446,7 @@ static int ccwchain_handle_ccw(u32 cda, struct channel_program *cp)
        struct ccwchain *chain;
        int len, ret;
 
-       /* Get chain length. */
+       /* Copy the chain from cda to cp, and count the CCWs in it */
        len = ccwchain_calc_length(cda, cp);
        if (len < 0)
                return len;

diff --git a/drivers/s390/cio/vfio_ccw_cp.h b/drivers/s390/cio/vfio_ccw_cp.h
index 3c20cd208da59e3bf78d4343447d3bb632a57a30..7cdc380490337a1dd75fb1936da37f8d6b7d3987 100644 (file)
--- a/drivers/s390/cio/vfio_ccw_cp.h
+++ b/drivers/s390/cio/vfio_ccw_cp.h
@@ -16,6 +16,12 @@
 
 #include "orb.h"
 
+/*
+ * Max length for ccw chain.
+ * XXX: Limit to 256, need to check more?
+ */
+#define CCWCHAIN_LEN_MAX       256
+
 /**
  * struct channel_program - manage information for channel program
  * @ccwchain_list: list head of ccwchains
@@ -32,6 +38,7 @@ struct channel_program {
        union orb orb;
        struct device *mdev;
        bool initialized;
+       struct ccw1 *guest_cp;
 };
 
 extern int cp_init(struct channel_program *cp, struct device *mdev,

diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
index 66a66ac1f3d128d9ba8e0ceff9ebc70dbc551419..34a9a5e3fd36eb7f2f96c44a9da5200c5151b469 100644 (file)
--- a/drivers/s390/cio/vfio_ccw_drv.c
+++ b/drivers/s390/cio/vfio_ccw_drv.c
@@ -129,6 +129,11 @@ static int vfio_ccw_sch_probe(struct subchannel *sch)
        if (!private)
                return -ENOMEM;
 
+       private->cp.guest_cp = kcalloc(CCWCHAIN_LEN_MAX, sizeof(struct ccw1),
+                                      GFP_KERNEL);
+       if (!private->cp.guest_cp)
+               goto out_free;
+
        private->io_region = kmem_cache_zalloc(vfio_ccw_io_region,
                                               GFP_KERNEL | GFP_DMA);
        if (!private->io_region)
@@ -169,6 +174,7 @@ out_free:
                kmem_cache_free(vfio_ccw_cmd_region, private->cmd_region);
        if (private->io_region)
                kmem_cache_free(vfio_ccw_io_region, private->io_region);
+       kfree(private->cp.guest_cp);
        kfree(private);
        return ret;
 }
@@ -185,6 +191,7 @@ static int vfio_ccw_sch_remove(struct subchannel *sch)
 
        kmem_cache_free(vfio_ccw_cmd_region, private->cmd_region);
        kmem_cache_free(vfio_ccw_io_region, private->io_region);
+       kfree(private->cp.guest_cp);
        kfree(private);
 
        return 0;