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authorCornelia Huck <cornelia.huck@de.ibm.com>2012-12-14 17:02:16 +0100
committerGleb Natapov <gleb@redhat.com>2012-12-18 13:36:38 +0100
commit55c171a6d90dc0574021f9c836127cfd1a7d2e30 (patch)
treeb13fae2636784f86aecf148beeb353bc21ac2531 /drivers/s390
parentkvm: fix i8254 counter 0 wraparound (diff)
downloadlinux-55c171a6d90dc0574021f9c836127cfd1a7d2e30.tar.xz
linux-55c171a6d90dc0574021f9c836127cfd1a7d2e30.zip
KVM: s390: Handle hosts not supporting s390-virtio.
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. Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com> Reviewed-by: Alexander Graf <agraf@suse.de> Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com> cc: stable@vger.kernel.org Signed-off-by: Gleb Natapov <gleb@redhat.com>
Diffstat (limited to 'drivers/s390')
-rw-r--r--drivers/s390/kvm/kvm_virtio.c38
1 files changed, 30 insertions, 8 deletions
diff --git a/drivers/s390/kvm/kvm_virtio.c b/drivers/s390/kvm/kvm_virtio.c
index 7dabef624da3..b846b6c4130a 100644
--- a/drivers/s390/kvm/kvm_virtio.c
+++ b/drivers/s390/kvm/kvm_virtio.c
@@ -422,6 +422,26 @@ 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
*/
@@ -432,21 +452,23 @@ static int __init kvm_devices_init(void)
if (!MACHINE_IS_KVM)
return -ENODEV;
+ if (test_devices_support(real_memory_size) < 0)
+ return -ENODEV;
+
+ 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();