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KVM: s390: Handle hosts not supporting s390-virtio.

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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>
This commit is contained in:
Cornelia Huck 2012-12-14 17:02:16 +01:00 committed by Gleb Natapov
parent d4b06c2d4c
commit 55c171a6d9
1 changed files with 30 additions and 8 deletions
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38
drivers/s390/kvm/kvm_virtio.c
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@ -421,6 +421,26 @@ 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();