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Reply-To: Sean Christopherson <seanjc@google.com>
Date:   Wed,  2 Nov 2022 23:18:37 +0000
In-Reply-To: <20221102231911.3107438-1-seanjc@google.com>
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Message-ID: <20221102231911.3107438-11-seanjc@google.com>
Subject: [PATCH 10/44] KVM: VMX: Clean up eVMCS enabling if KVM initialization fails
From:   Sean Christopherson <seanjc@google.com>
To:     Paolo Bonzini <pbonzini@redhat.com>, Marc Zyngier <maz@kernel.org>,
        Huacai Chen <chenhuacai@kernel.org>,
        Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>,
        Anup Patel <anup@brainfault.org>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Christian Borntraeger <borntraeger@linux.ibm.com>,
        Janosch Frank <frankja@linux.ibm.com>,
        Claudio Imbrenda <imbrenda@linux.ibm.com>,
        Matthew Rosato <mjrosato@linux.ibm.com>,
        Eric Farman <farman@linux.ibm.com>,
        Sean Christopherson <seanjc@google.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>
Cc:     James Morse <james.morse@arm.com>,
        Alexandru Elisei <alexandru.elisei@arm.com>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        Oliver Upton <oliver.upton@linux.dev>,
        Atish Patra <atishp@atishpatra.org>,
        David Hildenbrand <david@redhat.com>, kvm@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev,
        kvmarm@lists.cs.columbia.edu, linux-mips@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org,
        linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Isaku Yamahata <isaku.yamahata@intel.com>,
        Fabiano Rosas <farosas@linux.ibm.com>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Chao Gao <chao.gao@intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Yuan Yao <yuan.yao@intel.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

To make it obvious that KVM doesn't have a lurking bug, cleanup eVMCS
enabling if kvm_init() fails even though the enabling doesn't strictly
need to be unwound.  eVMCS enabling only toggles values that are fully
contained in the VMX module, i.e. it's technically ok to leave the values
as-is since they'll disappear entirely when the module is unloaded, but
doing proper cleanup is relatively simple, and having a chunk of code
that isn't unwound is confusing.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/vmx/vmx.c | 137 +++++++++++++++++++++++------------------
 1 file changed, 78 insertions(+), 59 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 05a747c9a9ff..b3fd4049de01 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -524,6 +524,8 @@ static inline void vmx_segment_cache_clear(struct vcpu_vmx *vmx)
 static unsigned long host_idt_base;
 
 #if IS_ENABLED(CONFIG_HYPERV)
+static struct kvm_x86_ops vmx_x86_ops __initdata;
+
 static bool __read_mostly enlightened_vmcs = true;
 module_param(enlightened_vmcs, bool, 0444);
 
@@ -552,6 +554,71 @@ static int hv_enable_direct_tlbflush(struct kvm_vcpu *vcpu)
 	return 0;
 }
 
+static __init void hv_setup_evmcs(void)
+{
+	int cpu;
+
+	if (!enlightened_vmcs)
+		return;
+
+	/*
+	 * Enlightened VMCS usage should be recommended and the host needs
+	 * to support eVMCS v1 or above.
+	 */
+	if (ms_hyperv.hints & HV_X64_ENLIGHTENED_VMCS_RECOMMENDED &&
+	    (ms_hyperv.nested_features & HV_X64_ENLIGHTENED_VMCS_VERSION) >=
+	     KVM_EVMCS_VERSION) {
+
+		/* Check that we have assist pages on all online CPUs */
+		for_each_online_cpu(cpu) {
+			if (!hv_get_vp_assist_page(cpu)) {
+				enlightened_vmcs = false;
+				break;
+			}
+		}
+
+		if (enlightened_vmcs) {
+			pr_info("KVM: vmx: using Hyper-V Enlightened VMCS\n");
+			static_branch_enable(&enable_evmcs);
+		}
+
+		if (ms_hyperv.nested_features & HV_X64_NESTED_DIRECT_FLUSH)
+			vmx_x86_ops.enable_direct_tlbflush
+				= hv_enable_direct_tlbflush;
+
+	} else {
+		enlightened_vmcs = false;
+	}
+}
+static void hv_cleanup_evmcs(void)
+{
+	struct hv_vp_assist_page *vp_ap;
+	int cpu;
+
+	if (!static_branch_unlikely(&enable_evmcs))
+		return;
+
+	/*
+	 * Reset everything to support using non-enlightened VMCS access later
+	 * (e.g. when we reload the module with enlightened_vmcs=0)
+	 */
+	for_each_online_cpu(cpu) {
+		vp_ap =	hv_get_vp_assist_page(cpu);
+
+		if (!vp_ap)
+			continue;
+
+		vp_ap->nested_control.features.directhypercall = 0;
+		vp_ap->current_nested_vmcs = 0;
+		vp_ap->enlighten_vmentry = 0;
+	}
+
+	static_branch_disable(&enable_evmcs);
+}
+
+#else /* IS_ENABLED(CONFIG_HYPERV) */
+static void hv_setup_evmcs(void) {}
+static void hv_cleanup_evmcs(void) {}
 #endif /* IS_ENABLED(CONFIG_HYPERV) */
 
 /*
@@ -8435,29 +8502,8 @@ static void vmx_exit(void)
 
 	kvm_exit();
 
-#if IS_ENABLED(CONFIG_HYPERV)
-	if (static_branch_unlikely(&enable_evmcs)) {
-		int cpu;
-		struct hv_vp_assist_page *vp_ap;
-		/*
-		 * Reset everything to support using non-enlightened VMCS
-		 * access later (e.g. when we reload the module with
-		 * enlightened_vmcs=0)
-		 */
-		for_each_online_cpu(cpu) {
-			vp_ap =	hv_get_vp_assist_page(cpu);
+	hv_cleanup_evmcs();
 
-			if (!vp_ap)
-				continue;
-
-			vp_ap->nested_control.features.directhypercall = 0;
-			vp_ap->current_nested_vmcs = 0;
-			vp_ap->enlighten_vmentry = 0;
-		}
-
-		static_branch_disable(&enable_evmcs);
-	}
-#endif
 	vmx_cleanup_l1d_flush();
 
 	allow_smaller_maxphyaddr = false;
@@ -8468,43 +8514,12 @@ static int __init vmx_init(void)
 {
 	int r, cpu;
 
-#if IS_ENABLED(CONFIG_HYPERV)
-	/*
-	 * Enlightened VMCS usage should be recommended and the host needs
-	 * to support eVMCS v1 or above. We can also disable eVMCS support
-	 * with module parameter.
-	 */
-	if (enlightened_vmcs &&
-	    ms_hyperv.hints & HV_X64_ENLIGHTENED_VMCS_RECOMMENDED &&
-	    (ms_hyperv.nested_features & HV_X64_ENLIGHTENED_VMCS_VERSION) >=
-	    KVM_EVMCS_VERSION) {
-
-		/* Check that we have assist pages on all online CPUs */
-		for_each_online_cpu(cpu) {
-			if (!hv_get_vp_assist_page(cpu)) {
-				enlightened_vmcs = false;
-				break;
-			}
-		}
-
-		if (enlightened_vmcs) {
-			pr_info("KVM: vmx: using Hyper-V Enlightened VMCS\n");
-			static_branch_enable(&enable_evmcs);
-		}
-
-		if (ms_hyperv.nested_features & HV_X64_NESTED_DIRECT_FLUSH)
-			vmx_x86_ops.enable_direct_tlbflush
-				= hv_enable_direct_tlbflush;
-
-	} else {
-		enlightened_vmcs = false;
-	}
-#endif
+	hv_setup_evmcs();
 
 	r = kvm_init(&vmx_init_ops, sizeof(struct vcpu_vmx),
 		     __alignof__(struct vcpu_vmx), THIS_MODULE);
 	if (r)
-		return r;
+		goto err_kvm_init;
 
 	/*
 	 * Must be called after kvm_init() so enable_ept is properly set
@@ -8514,10 +8529,8 @@ static int __init vmx_init(void)
 	 * mitigation mode.
 	 */
 	r = vmx_setup_l1d_flush(vmentry_l1d_flush_param);
-	if (r) {
-		vmx_exit();
-		return r;
-	}
+	if (r)
+		goto err_l1d_flush;
 
 	vmx_setup_fb_clear_ctrl();
 
@@ -8542,5 +8555,11 @@ static int __init vmx_init(void)
 		allow_smaller_maxphyaddr = true;
 
 	return 0;
+
+err_l1d_flush:
+	vmx_exit();
+err_kvm_init:
+	hv_cleanup_evmcs();
+	return r;
 }
 module_init(vmx_init);
-- 
2.38.1.431.g37b22c650d-goog