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Subject[PATCH v4 2/2] KVM: VMX: untangle VMXON revision_id setting when using eVMCS
Date
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 vmcs_type' parameter to alloc_vmcs_cpu()/alloc_vmcs().

No functional change intended.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
arch/x86/kvm/vmx/nested.c | 2 +-
arch/x86/kvm/vmx/vmx.c | 34 +++++++++++++++-------------------
arch/x86/kvm/vmx/vmx.h | 12 +++++++++---
3 files changed, 25 insertions(+), 23 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 8578513907d7..7170c7d8aa1d 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -4585,7 +4585,7 @@ static struct vmcs *alloc_shadow_vmcs(struct kvm_vcpu *vcpu)
WARN_ON(loaded_vmcs == &vmx->vmcs01 && loaded_vmcs->shadow_vmcs);

if (!loaded_vmcs->shadow_vmcs) {
- loaded_vmcs->shadow_vmcs = alloc_vmcs(true);
+ loaded_vmcs->shadow_vmcs = alloc_vmcs(SHADOW_VMCS);
if (loaded_vmcs->shadow_vmcs)
vmcs_clear(loaded_vmcs->shadow_vmcs);
}
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index f7ee7c31fe8c..534418b58247 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2541,7 +2541,7 @@ 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_vmcs_cpu(enum vmcs_type type, int cpu, gfp_t flags)
{
int node = cpu_to_node(cpu);
struct page *pages;
@@ -2553,13 +2553,21 @@ 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_VMCS && 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)
vmcs->hdr.shadow_vmcs = 1;
return vmcs;
}
@@ -2586,7 +2594,7 @@ void free_loaded_vmcs(struct loaded_vmcs *loaded_vmcs)

int alloc_loaded_vmcs(struct loaded_vmcs *loaded_vmcs)
{
- loaded_vmcs->vmcs = alloc_vmcs(false);
+ loaded_vmcs->vmcs = alloc_vmcs(VMCS);
if (!loaded_vmcs->vmcs)
return -ENOMEM;

@@ -2639,25 +2647,13 @@ static __init int alloc_vmxon_regions(void)
for_each_possible_cpu(cpu) {
struct vmcs *vmcs;

- vmcs = alloc_vmcs_cpu(false, cpu, GFP_KERNEL);
+ /* The VMXON region is really just a special type of VMCS. */
+ vmcs = alloc_vmcs_cpu(VMXON_VMCS, 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 be93d597306c..b353e8cc3e7b 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -488,16 +488,22 @@ 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 vmcs_type {
+ VMXON_VMCS,
+ VMCS,
+ SHADOW_VMCS,
+};
+
+struct vmcs *alloc_vmcs_cpu(enum vmcs_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);
void loaded_vmcs_init(struct loaded_vmcs *loaded_vmcs);
void loaded_vmcs_clear(struct loaded_vmcs *loaded_vmcs);

-static inline struct vmcs *alloc_vmcs(bool shadow)
+static inline struct vmcs *alloc_vmcs(enum vmcs_type type)
{
- return alloc_vmcs_cpu(shadow, raw_smp_processor_id(),
+ return alloc_vmcs_cpu(type, raw_smp_processor_id(),
GFP_KERNEL_ACCOUNT);
}

--
2.25.1
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