linux-kernel - Re: RFC: silencing kvm unimplemented msr spew.

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Message-ID: <20160721202440.GA10908@fb.com>
Date:	Thu, 21 Jul 2016 16:24:40 -0400
From:	Dave Jones <dsj@...com>
To:	Bandan Das <bsd@...hat.com>
CC:	Paolo Bonzini <pbonzini@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Radim Krčmář <rkrcmar@...hat.com>,
	<kvm@...r.kernel.org>
Subject: Re: RFC: silencing kvm unimplemented msr spew.

On Tue, Jul 19, 2016 at 04:24:31PM -0400, Bandan Das wrote:

 > Heh, actually after speaking about this to Paolo a while back, I had this sleeping
 > in my local branch for a while. Same as what you suggested (without the ratelimiting)
 > 
 > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
 > index def97b3..c6e6f64 100644
 > --- a/arch/x86/kvm/mmu.c
 > +++ b/arch/x86/kvm/mmu.c
 > @@ -4952,7 +4952,7 @@ void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm, struct kvm_memslots *slots)
 >          * zap all shadow pages.
 >          */
 >         if (unlikely((slots->generation & MMIO_GEN_MASK) == 0)) {
 > -               printk_ratelimited(KERN_DEBUG "kvm: zapping shadow pages for mmio generation wraparound\n");
 > +               kvm_debug("zapping shadow pages for mmio generation wraparound\n");
 >                 kvm_mmu_invalidate_zap_all_pages(kvm);
 >         }
 >  }
 > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
 > index 7da5dd2..02d09f9 100644
 > --- a/arch/x86/kvm/x86.c
 > +++ b/arch/x86/kvm/x86.c
 > @@ -2229,7 +2229,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 >                 if (kvm_pmu_is_valid_msr(vcpu, msr))
 >                         return kvm_pmu_set_msr(vcpu, msr_info);
 >                 if (!ignore_msrs) {
 > -                       vcpu_unimpl(vcpu, "unhandled wrmsr: 0x%x data %llx\n",
 > +                       vcpu_debug(vcpu, "unhandled wrmsr: 0x%x data %llx\n",
 >                                     msr, data);
 >                         return 1;
 >                 } else {
 > @@ -2441,7 +2441,7 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 >                 if (kvm_pmu_is_valid_msr(vcpu, msr_info->index))
 >                         return kvm_pmu_get_msr(vcpu, msr_info->index, &msr_info->data);
 >                 if (!ignore_msrs) {
 > -                       vcpu_unimpl(vcpu, "unhandled rdmsr: 0x%x\n", msr_info->index);
 > +                       vcpu_debug(vcpu, "unhandled rdmsr: 0x%x\n", msr_info->index);
 >                         return 1;
 >                 } else {
 >                         vcpu_unimpl(vcpu, "ignored rdmsr: 0x%x\n", msr_info->index);
 > 
 > I had the same reasoning regarding  dynamic debugging which I think is
 > enabled by default on most builds anyway.

Yeah, that's close. Though I would have done the same for the other side of the if's too.
(Still evaluating which mode is actually more useful for us).

Paolo, would you prefer this, or the other approach you already ack'd ?

	Dave