linux-kernel - [PATCH 2/2] KVM: x86: VMX: untangle VMXON revision

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Date:   Thu,  5 Mar 2020 11:01:23 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] KVM: x86: VMX: untangle VMXON revision_id setting when using eVMCS

As stated in alloc_vmxon_regions(), VMXON region needs to be tagged with
revision id from MSR_IA32_VMX_BASIC even in case of eVMCS. The logic to
do so is not very straightforward: first, we set
hdr.revision_id = KVM_EVMCS_VERSION in alloc_vmcs_cpu() just to reset it
back to vmcs_config.revision_id in alloc_vmxon_regions(). Simplify this by
introducing 'enum vmx_area_type' parameter to what is now known as
alloc_vmx_area_cpu().

No functional change intended.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/kvm/vmx/vmx.c | 31 +++++++++++++------------------
 arch/x86/kvm/vmx/vmx.h | 12 +++++++++---
 2 files changed, 22 insertions(+), 21 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index dab19e4e5f2b..4ee19fb35cde 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2554,7 +2554,7 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf,
 	return 0;
 }
 
-struct vmcs *alloc_vmcs_cpu(bool shadow, int cpu, gfp_t flags)
+struct vmcs *alloc_vmx_area_cpu(enum vmx_area_type type, int cpu, gfp_t flags)
 {
 	int node = cpu_to_node(cpu);
 	struct page *pages;
@@ -2566,13 +2566,21 @@ struct vmcs *alloc_vmcs_cpu(bool shadow, int cpu, gfp_t flags)
 	vmcs = page_address(pages);
 	memset(vmcs, 0, vmcs_config.size);
 
-	/* KVM supports Enlightened VMCS v1 only */
-	if (static_branch_unlikely(&enable_evmcs))
+	/*
+	 * When eVMCS is enabled, vmcs->revision_id needs to be set to the
+	 * supported eVMCS version (KVM_EVMCS_VERSION) instead of revision_id
+	 * reported by MSR_IA32_VMX_BASIC.
+	 *
+	 * However, even though not explicitly documented by TLFS, VMXArea
+	 * passed as VMXON argument should still be marked with revision_id
+	 * reported by physical CPU.
+	 */
+	if (type != VMXON_REGION && static_branch_unlikely(&enable_evmcs))
 		vmcs->hdr.revision_id = KVM_EVMCS_VERSION;
 	else
 		vmcs->hdr.revision_id = vmcs_config.revision_id;
 
-	if (shadow)
+	if (type == SHADOW_VMCS_REGION)
 		vmcs->hdr.shadow_vmcs = 1;
 	return vmcs;
 }
@@ -2652,25 +2660,12 @@ static __init int alloc_vmxon_regions(void)
 	for_each_possible_cpu(cpu) {
 		struct vmcs *vmcs;
 
-		vmcs = alloc_vmcs_cpu(false, cpu, GFP_KERNEL);
+		vmcs = alloc_vmx_area_cpu(VMXON_REGION, cpu, GFP_KERNEL);
 		if (!vmcs) {
 			free_vmxon_regions();
 			return -ENOMEM;
 		}
 
-		/*
-		 * When eVMCS is enabled, alloc_vmcs_cpu() sets
-		 * vmcs->revision_id to KVM_EVMCS_VERSION instead of
-		 * revision_id reported by MSR_IA32_VMX_BASIC.
-		 *
-		 * However, even though not explicitly documented by
-		 * TLFS, VMXArea passed as VMXON argument should
-		 * still be marked with revision_id reported by
-		 * physical CPU.
-		 */
-		if (static_branch_unlikely(&enable_evmcs))
-			vmcs->hdr.revision_id = vmcs_config.revision_id;
-
 		per_cpu(vmxarea, cpu) = vmcs;
 	}
 	return 0;
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index e64da06c7009..7bdac5a50432 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -489,7 +489,13 @@ static inline struct pi_desc *vcpu_to_pi_desc(struct kvm_vcpu *vcpu)
 	return &(to_vmx(vcpu)->pi_desc);
 }
 
-struct vmcs *alloc_vmcs_cpu(bool shadow, int cpu, gfp_t flags);
+enum vmx_area_type {
+	VMXON_REGION,
+	VMCS_REGION,
+	SHADOW_VMCS_REGION,
+};
+
+struct vmcs *alloc_vmx_area_cpu(enum vmx_area_type type, int cpu, gfp_t flags);
 void free_vmcs(struct vmcs *vmcs);
 int alloc_loaded_vmcs(struct loaded_vmcs *loaded_vmcs);
 void free_loaded_vmcs(struct loaded_vmcs *loaded_vmcs);
@@ -498,8 +504,8 @@ void loaded_vmcs_clear(struct loaded_vmcs *loaded_vmcs);
 
 static inline struct vmcs *alloc_vmcs(bool shadow)
 {
-	return alloc_vmcs_cpu(shadow, raw_smp_processor_id(),
-			      GFP_KERNEL_ACCOUNT);
+	return alloc_vmx_area_cpu(shadow ? SHADOW_VMCS_REGION : VMCS_REGION,
+				  raw_smp_processor_id(), GFP_KERNEL_ACCOUNT);
 }
 
 u64 construct_eptp(struct kvm_vcpu *vcpu, unsigned long root_hpa);
-- 
2.24.1