Running under a kvm host does not necessarily imply the presence of
a page mapped above the main memory with the virtio information;
however, the code includes a hard coded access to that page.
Instead, check for the presence of the page and exit gracefully
before we hit an addressing exception if it does not exist.
Signed-off-by: Cornelia Huck <cornelia.huck@xxxxxxxxxx>
---
Changes v1->v2:
- check for the presence of the patch with lura
- reorder init sequence
- comments
---
drivers/s390/kvm/kvm_virtio.c | 39 +++++++++++++++++++++++++++++++--------
1 file changed, 31 insertions(+), 8 deletions(-)
diff --git a/drivers/s390/kvm/kvm_virtio.c b/drivers/s390/kvm/kvm_virtio.c
index 47cccd5..76b95f3 100644
--- a/drivers/s390/kvm/kvm_virtio.c
+++ b/drivers/s390/kvm/kvm_virtio.c
@@ -419,6 +419,26 @@ static void kvm_extint_handler(struct ext_code ext_code,
}
/*
+ * For s390-virtio, we expect a page above main storage containing
+ * the virtio configuration. Try to actually load from this area
+ * in order to figure out if the host provides this page.
+ */
+static int __init test_devices_support(unsigned long addr)
+{
+ int ret = -EIO;
+
+ asm volatile(
+ "0: lura 0,%1\n"
+ "1: xgr %0,%0\n"
+ "2:\n"
+ EX_TABLE(0b,2b)
+ EX_TABLE(1b,2b)
+ : "+d" (ret)
+ : "a" (addr)
+ : "0", "cc");
+ return ret;
+}
+/*
* Init function for virtio
* devices are in a single page above top of "normal" mem
*/
@@ -429,21 +449,24 @@ static int __init kvm_devices_init(void)
if (!MACHINE_IS_KVM)
return -ENODEV;
+ if (test_devices_support(real_memory_size) < 0)
+ /* No error. */
+ return 0;
+
+ rc = vmem_add_mapping(real_memory_size, PAGE_SIZE);
+ if (rc)
+ return rc;
+
+ kvm_devices = (void *) real_memory_size;
+
kvm_root = root_device_register("kvm_s390");
if (IS_ERR(kvm_root)) {
rc = PTR_ERR(kvm_root);
printk(KERN_ERR "Could not register kvm_s390 root device");
+ vmem_remove_mapping(real_memory_size, PAGE_SIZE);
return rc;
}
- rc = vmem_add_mapping(real_memory_size, PAGE_SIZE);
- if (rc) {
- root_device_unregister(kvm_root);
- return rc;
- }
-
- kvm_devices = (void *) real_memory_size;
-
INIT_WORK(&hotplug_work, hotplug_devices);
service_subclass_irq_register();
--
1.7.11.5
--
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