From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S967497AbeBNLch (ORCPT ); Wed, 14 Feb 2018 06:32:37 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:44104 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S967342AbeBNLcd (ORCPT ); Wed, 14 Feb 2018 06:32:33 -0500 Subject: Re: [patch] kvm: suppress KVM_SET_GSI_ROUTING allocation failure To: Christian Borntraeger , David Rientjes Cc: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , linux-kernel@vger.kernel.org, kvm@vger.kernel.org References: <47a55220-0006-6486-5a9d-1d1142efcc47@de.ibm.com> <179c1c39-2b3f-20f6-d4cb-0044aa49e570@redhat.com> From: Paolo Bonzini Message-ID: <55452103-8c14-19df-38d8-99459e9abd6a@redhat.com> Date: Wed, 14 Feb 2018 12:32:29 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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