| From | Luis Henriques <> | Subject | [PATCH 002/139] KVM: s390: Handle hosts not supporting s390-virtio. | Date | Thu, 28 Feb 2013 14:42:32 +0000 |
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3.5.7.7 -stable review patch. If anyone has any objections, please let me know.
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From: Cornelia Huck <cornelia.huck@de.ibm.com>
commit 55c171a6d90dc0574021f9c836127cfd1a7d2e30 upstream.
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> Signed-off-by: Gleb Natapov <gleb@redhat.com> Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- drivers/s390/kvm/kvm_virtio.c | 38 ++++++++++++++++++++++++++++++-------- 1 file changed, 30 insertions(+), 8 deletions(-)
diff --git a/drivers/s390/kvm/kvm_virtio.c b/drivers/s390/kvm/kvm_virtio.c index d74e9ae..f97b2aa 100644 --- a/drivers/s390/kvm/kvm_virtio.c +++ b/drivers/s390/kvm/kvm_virtio.c @@ -418,6 +418,26 @@ 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 */ @@ -428,21 +448,23 @@ 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(); -- 1.8.1.2
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