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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.googlemail.com with ESMTPSA id e5-20020a170906374500b006d5825520a7sm752037ejc.71.2022.03.09.05.42.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 09 Mar 2022 05:42:03 -0800 (PST) Sender: Paolo Bonzini Message-ID: <68233503-3ac5-9161-c83d-6b8189dedc8f@redhat.com> Date: Wed, 9 Mar 2022 14:41:59 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [PATCH v3 6/7] KVM: x86: SVM: allow to force AVIC to be enabled Content-Language: en-US To: Maxim Levitsky , kvm@vger.kernel.org Cc: Ingo Molnar , Dave Hansen , Sean Christopherson , Borislav Petkov , "H. Peter Anvin" , Thomas Gleixner , Jim Mattson , x86@kernel.org, Vitaly Kuznetsov , Joerg Roedel , linux-kernel@vger.kernel.org, Wanpeng Li References: <20220301143650.143749-1-mlevitsk@redhat.com> <20220301143650.143749-7-mlevitsk@redhat.com> From: Paolo Bonzini In-Reply-To: <20220301143650.143749-7-mlevitsk@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/1/22 15:36, Maxim Levitsky wrote: > Apparently on some systems AVIC is disabled in CPUID but still usable. > > Allow the user to override the CPUID if the user is willing to > take the risk. > > Signed-off-by: Maxim Levitsky > --- > arch/x86/kvm/svm/svm.c | 11 +++++++++-- > 1 file changed, 9 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c > index 776585dd77769..a26b4c899899e 100644 > --- a/arch/x86/kvm/svm/svm.c > +++ b/arch/x86/kvm/svm/svm.c > @@ -202,6 +202,9 @@ module_param(tsc_scaling, int, 0444); > static bool avic; > module_param(avic, bool, 0444); > > +static bool force_avic; > +module_param_unsafe(force_avic, bool, 0444); > + > bool __read_mostly dump_invalid_vmcb; > module_param(dump_invalid_vmcb, bool, 0644); > > @@ -4896,10 +4899,14 @@ static __init int svm_hardware_setup(void) > nrips = false; > } > > - enable_apicv = avic = avic && npt_enabled && boot_cpu_has(X86_FEATURE_AVIC); > + enable_apicv = avic = avic && npt_enabled && (boot_cpu_has(X86_FEATURE_AVIC) || force_avic); > > if (enable_apicv) { > - pr_info("AVIC enabled\n"); > + if (!boot_cpu_has(X86_FEATURE_AVIC)) { > + pr_warn("AVIC is not supported in CPUID but force enabled"); > + pr_warn("Your system might crash and burn"); > + } else > + pr_info("AVIC enabled\n"); > > amd_iommu_register_ga_log_notifier(&avic_ga_log_notifier); > } else { Queued, thanks. Paolo