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Thu, 17 Nov 2022 11:26:55 -0800 (PST) Received: from localhost ([192.55.54.55]) by smtp.gmail.com with ESMTPSA id qe1-20020a17090b4f8100b00210039560c0sm3940135pjb.49.2022.11.17.11.26.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 17 Nov 2022 11:26:54 -0800 (PST) Date: Thu, 17 Nov 2022 11:26:53 -0800 From: Isaku Yamahata To: Chenyi Qiang Cc: isaku.yamahata@intel.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, isaku.yamahata@gmail.com, Paolo Bonzini , erdemaktas@google.com, Sean Christopherson , Sagi Shahar , David Matlack , Kai Huang Subject: Re: [PATCH v10 049/108] KVM: x86/tdp_mmu: Support TDX private mapping for TDP MMU Message-ID: <20221117192653.GM2350331@ls.amr.corp.intel.com> References: <9d5595dfe1b5ab77bcb5650bc4d940dd977b0a32.1667110240.git.isaku.yamahata@intel.com> <67b782ee-c95c-d6bc-3cca-cdfe75f4bf6a@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <67b782ee-c95c-d6bc-3cca-cdfe75f4bf6a@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 16, 2022 at 09:40:38AM +0800, Chenyi Qiang wrote: > > +static int __must_check handle_changed_private_spte(struct kvm *kvm, gfn_t gfn, > > + u64 old_spte, u64 new_spte, > > + int level) > > +{ > > + bool was_present = is_shadow_present_pte(old_spte); > > + bool is_present = is_shadow_present_pte(new_spte); > > + bool was_leaf = was_present && is_last_spte(old_spte, level); > > + bool is_leaf = is_present && is_last_spte(new_spte, level); > > + kvm_pfn_t old_pfn = spte_to_pfn(old_spte); > > + kvm_pfn_t new_pfn = spte_to_pfn(new_spte); > > + int ret; > > int ret = 0; > > > + > > + lockdep_assert_held(&kvm->mmu_lock); > > + if (is_present) { > > + /* TDP MMU doesn't change present -> present */ > > + KVM_BUG_ON(was_present, kvm); > > + > > + /* > > + * Use different call to either set up middle level > > + * private page table, or leaf. > > + */ > > + if (is_leaf) > > + ret = static_call(kvm_x86_set_private_spte)(kvm, gfn, level, new_pfn); > > + else { > > + void *private_spt = get_private_spt(gfn, new_spte, level); > > + > > + KVM_BUG_ON(!private_spt, kvm); > > + ret = static_call(kvm_x86_link_private_spt)(kvm, gfn, level, private_spt); > > + } > > + } else if (was_leaf) { > > + /* non-present -> non-present doesn't make sense. */ > > + KVM_BUG_ON(!was_present, kvm); > > + /* > > + * Zap private leaf SPTE. Zapping private table is done > > + * below in handle_removed_tdp_mmu_page(). > > + */ > > + lockdep_assert_held_write(&kvm->mmu_lock); > > + ret = static_call(kvm_x86_zap_private_spte)(kvm, gfn, level); > > + if (!ret) { > > + ret = static_call(kvm_x86_remove_private_spte)(kvm, gfn, level, old_pfn); > > + WARN_ON_ONCE(ret); > > + } > > + } > > Otherwise, "ret" may be returned without initialization. Then it will > trigger the WARN_ON_ONCE(ret) after handle_changed_spte() in patch 48. Thanks for catching it. Compiler didn't complain it. Maybe W=1 is needed. -- Isaku Yamahata