3 files changed, 20 insertions, 6 deletions
diff --git a/pc-bios/s390-ccw/s390-ccw.h b/pc-bios/s390-ccw/s390-ccw.h
index 6fdc8589cf..25d4d213ea 100644
--- a/pc-bios/s390-ccw/s390-ccw.h
+++ b/pc-bios/s390-ccw/s390-ccw.h
@@ -44,6 +44,8 @@ typedef unsigned long long __u64;
                             ((b) == 0 ? (a) : (MIN(a, b))))
 #endif
 
+#define ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]))
+
 #include "cio.h"
 #include "iplb.h"
 
diff --git a/pc-bios/s390-ccw/virtio.c b/pc-bios/s390-ccw/virtio.c
index 9d9e61faa3..18fc5d1672 100644
--- a/pc-bios/s390-ccw/virtio.c
+++ b/pc-bios/s390-ccw/virtio.c
@@ -12,6 +12,7 @@
 #include "s390-ccw.h"
 #include "virtio.h"
 #include "virtio-scsi.h"
+#include "bswap.h"
 
 #define VRING_WAIT_REPLY_TIMEOUT 3
 
@@ -249,8 +250,12 @@ int virtio_run(VDev *vdev, int vqid, VirtioCmd *cmd)
 
 void virtio_setup_ccw(VDev *vdev)
 {
-    int i, cfg_size = 0;
+    int i, rc, cfg_size = 0;
     unsigned char status = VIRTIO_CONFIG_S_DRIVER_OK;
+    struct VirtioFeatureDesc {
+        uint32_t features;
+        uint8_t index;
+    } __attribute__((packed)) feats;
 
     IPL_assert(virtio_is_supported(vdev->schid), "PE");
     /* device ID has been established now */
@@ -277,11 +282,17 @@ void virtio_setup_ccw(VDev *vdev)
     IPL_assert(run_ccw(vdev, CCW_CMD_READ_CONF, &vdev->config, cfg_size) == 0,
                "Could not get block device configuration");
 
-    /*
-     * Skipping CCW_CMD_READ_FEAT. We're not doing anything fancy, and
-     * we'll just stop dead anyway if anything does not work like we
-     * expect it.
-     */
+    /* Feature negotiation */
+    for (i = 0; i < ARRAY_SIZE(vdev->guest_features); i++) {
+        feats.features = 0;
+        feats.index = i;
+        rc = run_ccw(vdev, CCW_CMD_READ_FEAT, &feats, sizeof(feats));
+        IPL_assert(rc == 0, "Could not get features bits");
+        vdev->guest_features[i] &= bswap32(feats.features);
+        feats.features = bswap32(vdev->guest_features[i]);
+        rc = run_ccw(vdev, CCW_CMD_WRITE_FEAT, &feats, sizeof(feats));
+        IPL_assert(rc == 0, "Could not set features bits");
+    }
 
     for (i = 0; i < vdev->nr_vqs; i++) {
         VqInfo info = {
diff --git a/pc-bios/s390-ccw/virtio.h b/pc-bios/s390-ccw/virtio.h
index d7337803ee..a00a320968 100644
--- a/pc-bios/s390-ccw/virtio.h
+++ b/pc-bios/s390-ccw/virtio.h
@@ -251,6 +251,7 @@ struct VDev {
     ScsiDevice selected_scsi_device;
     uint64_t netboot_start_addr;
     uint32_t max_transfer;
+    uint32_t guest_features[2];
 };
 typedef struct VDev VDev;