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AJvYcCW5gTSNBOwts/zVqi3vBDKPk2xvoy04NzYbGeaSOcSO9chUqou3QgOMSIFeAlb3D3YO86g9G+Hkz+xv81KwdKate2jvZENTEWKbl/9Z X-Gm-Message-State: AOJu0Yxf/tMn5cWsG7/lKG75qcejpNFiIfYA1Q8vXfoysYuEk/p8gUNm fXI59b0X4khuY6f7JLOGUd25C4IjSH/xliJIVNkCwxRRc4L0MlBxiG4ivoJcAzd+XAsnq7X93Zc p/A== X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a0d:d513:0:b0:604:103:567d with SMTP id x19-20020a0dd513000000b006040103567dmr152824ywd.0.1707517253085; Fri, 09 Feb 2024 14:20:53 -0800 (PST) Reply-To: Sean Christopherson Date: Fri, 9 Feb 2024 14:20:47 -0800 In-Reply-To: <20240209222047.394389-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240209222047.394389-1-seanjc@google.com> X-Mailer: git-send-email 2.43.0.687.g38aa6559b0-goog Message-ID: <20240209222047.394389-3-seanjc@google.com> Subject: [PATCH 2/2] KVM: x86: Sanity check that kvm_has_noapic_vcpu is zero at module_exit() From: Sean Christopherson To: Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Li RongQing , Maxim Levitsky X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1790461770774501546 X-GMAIL-MSGID: 1790461770774501546 WARN if kvm.ko is unloaded with an elevated kvm_has_noapic_vcpu to guard against incorrect management of the key, e.g. to detect if KVM fails to decrement the key in error paths. Because kvm_has_noapic_vcpu is purely an optimization, in all likelihood KVM could completely botch handling of kvm_has_noapic_vcpu and no one would notice (which is a good argument for deleting the key entirely, but that's a problem for another day). Note, ideally the sanity check would be performance when kvm_usage_count goes to zero, but adding an arch callback just for this sanity check isn't at all worth doing. Signed-off-by: Sean Christopherson --- arch/x86/kvm/x86.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 59119157bd20..779a5b32a5bf 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -13878,9 +13878,6 @@ module_init(kvm_x86_init); static void __exit kvm_x86_exit(void) { - /* - * If module_init() is implemented, module_exit() must also be - * implemented to allow module unload. - */ + WARN_ON_ONCE(static_branch_unlikely(&kvm_has_noapic_vcpu)); } module_exit(kvm_x86_exit);