From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sean Christopherson Date: Wed, 18 Dec 2019 21:55:06 +0000 Subject: [PATCH v2 21/45] KVM: x86: Remove spurious clearing of async #PF MSR Message-Id: <20191218215530.2280-22-sean.j.christopherson@intel.com> List-Id: References: <20191218215530.2280-1-sean.j.christopherson@intel.com> In-Reply-To: <20191218215530.2280-1-sean.j.christopherson@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Marc Zyngier , James Hogan , Paul Mackerras , Christian Borntraeger , Janosch Frank , Paolo Bonzini Cc: James Morse , Julien Thierry , Suzuki K Poulose , David Hildenbrand , Cornelia Huck , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-mips@vger.kernel.org, kvm-ppc@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Greg Kurz Remove a bogus clearing of apf.msr_val from kvm_arch_vcpu_destroy(). apf.msr_val is only set to a non-zero value by kvm_pv_enable_async_pf(), which is only reachable by kvm_set_msr_common(), i.e. by writing MSR_KVM_ASYNC_PF_EN. KVM does not autonomously write said MSR, i.e. can only be written via KVM_SET_MSRS or KVM_RUN. Since KVM_SET_MSRS and KVM_RUN are vcpu ioctls, they require a valid vcpu file descriptor. kvm_arch_vcpu_destroy() is only called if KVM_CREATE_VCPU fails, and KVM declares KVM_CREATE_VCPU successful once the vcpu fd is installed and thus visible to userspace. Ergo, apf.msr_val cannot be non-zero when kvm_arch_vcpu_destroy() is called. Fixes: 344d9588a9df0 ("KVM: Add PV MSR to enable asynchronous page faults delivery.") Signed-off-by: Sean Christopherson --- arch/x86/kvm/x86.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 19c14b786255..46626b52a4da 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -9176,8 +9176,6 @@ void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu) void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu) { - vcpu->arch.apf.msr_val = 0; - kvm_arch_vcpu_free(vcpu); } -- 2.24.1