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([2001:b07:6468:f312:75e3:aaa7:77d6:f4e4]) by smtp.gmail.com with ESMTPSA id o4sm4123220wrv.86.2020.09.30.10.39.38 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 30 Sep 2020 10:39:38 -0700 (PDT) Subject: Re: [PATCH 03/22] kvm: mmu: Init / Uninit the TDP MMU To: Sean Christopherson , Ben Gardon Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Cannon Matthews , Peter Xu , Peter Shier , Peter Feiner , Junaid Shahid , Jim Mattson , Yulei Zhang , Wanpeng Li , Vitaly Kuznetsov , Xiao Guangrong References: <20200925212302.3979661-1-bgardon@google.com> <20200925212302.3979661-4-bgardon@google.com> <20200930165734.GE32672@linux.intel.com> From: Paolo Bonzini Message-ID: <2633cc07-f106-25ba-0ab9-d4a422aca171@redhat.com> Date: Wed, 30 Sep 2020 19:39:38 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20200930165734.GE32672@linux.intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 30/09/20 18:57, Sean Christopherson wrote: >> + >> +static bool __read_mostly tdp_mmu_enabled = true; >> +module_param_named(tdp_mmu, tdp_mmu_enabled, bool, 0644); > This param should not exist until the TDP MMU is fully functional, e.g. running > KVM against "kvm: mmu: Support zapping SPTEs in the TDP MMU" immediately hits a > BUG() in the rmap code. I haven't wrapped my head around the entire series to > grok whether it make sense to incrementally enable the TDP MMU, but my gut says > that's probably non-sensical. No, it doesn't. Whether to add the module parameter is kind of secondary, but I agree it shouldn't be true---not even at the end of this series, since fast page fault for example is not implemented yet. Paolo