From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Jones Subject: Re: RFC: silencing kvm unimplemented msr spew. Date: Tue, 19 Jul 2016 15:58:56 -0400 Message-ID: <20160719195856.GA31453@fb.com> References: <20160715192729.GA4712@fb.com> <110045299.8101686.1468855610053.JavaMail.zimbra@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Cc: Linux Kernel , Radim =?utf-8?B?S3LEjW3DocWZ?= , To: Paolo Bonzini Return-path: Content-Disposition: inline In-Reply-To: <110045299.8101686.1468855610053.JavaMail.zimbra@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Mon, Jul 18, 2016 at 11:26:50AM -0400, Paolo Bonzini wrote: > > > kvm is pretty noisy when you have guests poking at MSRs that the kernel > > doesn't implement. The conveniently named 'ignore_msrs' option initially > > seemed > > like it was what I was looking for, but it changes the printk instead > > of eliding it. > > > > Untested patch below converts ignore_msrs to a bitmask and adds an option to > > be > > completely silent. The idea being if after testing, things still work and you > > don't care about those messages, you can deploy in production with the > > silence option. > > > > Would something like this be acceptable ? > > Indeed, ignore_msrs does a completely different thing. It suppresses > general protection faults in the guest. It is related to behavior that > KVM injects in the guests, not to the things that KVM spews in the host. > > What about just downgrading the printf to KERN_DEBUG? You could simply > change from vcpu_unimpl to vcpu_debug, but it's probably a good idea to > keep the ratelimiting; there's a kvm_pr_unimpl, so maybe add a new > kvm_pr_debug and vcpu_pr_debug. Hm, we've certainly got a lot of options in terms of print primitives these days. We could just do this... diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 1c9c973a7dd9..a80b9a0a5f8c 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -423,7 +423,7 @@ struct kvm { #define kvm_debug(fmt, ...) \ pr_debug("kvm [%i]: " fmt, task_pid_nr(current), ## __VA_ARGS__) #define kvm_pr_unimpl(fmt, ...) \ - pr_err_ratelimited("kvm [%i]: " fmt, \ + pr_debug_ratelimited("kvm [%i]: " fmt, \ task_tgid_nr(current), ## __VA_ARGS__) /* The guest did something we don't support. */ Which I think would have the desired effect, and also gets us dynamic debug support for free. Thoughts ? Dave