On 14/02/2018 12:14, Christian Borntraeger wrote: > > > On 02/14/2018 11:10 AM, Paolo Bonzini wrote: >> On 14/02/2018 02:03, David Rientjes wrote: >>> On Tue, 13 Feb 2018, Paolo Bonzini wrote: >>> >>>>>> The KVM_SET_GSI_ROUTING ioctl does a vmalloc() of >>>>>> sizeof(struct kvm_irq_routing_entry) multiplied by a user-supplied value. >>>>>> This can be up to 4096 entries on architectures such as arm64 and s390 >>>>>> (and the upper bound may be increased on s390 eventually). >>>>>> >>>>>> This can produce a vmalloc allocation failure warning: >>>>>> >>>>> [...] >>>>>> kvm_vm_ioctl+0x910/0x15e0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:4153 >>>>> >>>>> ^^^^^ >>>>> >>>>>> @@ -3063,7 +3063,8 @@ static long kvm_vm_ioctl(struct file *filp, >>>>> >>>>> ^^^^^ >>>>> >>>>> >>>>> Are you sure that you got the right vmalloc? >>>> >>>> Nice catch! But well, it's the only one in the whole file. :) >>>> >>>> That seems very much like an old patch then. I'm unqueuing it. >>>> >>> >>> It's not a catch at all, the fact that I saw this warning with an older >>> kernel for KVM_SET_GSI_ROUTING doesn't mean that I can't patch it with an >>> upstream kernel. Would you prefer I remove the stack trace completely? >> >> The upstream kernel doesn't warn. It checks "if (routing.nr)" before >> calling vmalloc. > > It will warn of the vmalloc space is really exhausted. But then I really ask > myself if we really want to suppress this warning. This should be a big > ALERT to the host admin. Especially since the biggest allocation KVM_SET_GSI_ROUTING can do is 128 KiB... Paolo
