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Date: Sat, 11 Feb 2023 00:35:33 +0000
From: Sean Christopherson <seanjc@...gle.com>
To: Vitaly Kuznetsov <vkuznets@...hat.com>,
Sean Christopherson <seanjc@...gle.com>,
Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/3] KVM: VMX: Stub out enable_evmcs static key for CONFIG_HYPERV=n
Wrap enable_evmcs in a helper and stub it out when CONFIG_HYPERV=n in
order to eliminate the static branch nop placeholders. clang-14 is clever
enough to elide the nop, but gcc-12 is not. Stubbing out the key reduces
the size of kvm-intel.ko by ~7.5% (200KiB) when compiled with gcc-12
(there are a _lot_ of VMCS accesses throughout KVM).
Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
arch/x86/kvm/vmx/hyperv.c | 4 ++--
arch/x86/kvm/vmx/hyperv.h | 10 ++++++++--
arch/x86/kvm/vmx/vmx.c | 15 +++++++--------
arch/x86/kvm/vmx/vmx_ops.h | 22 +++++++++++-----------
4 files changed, 28 insertions(+), 23 deletions(-)
diff --git a/arch/x86/kvm/vmx/hyperv.c b/arch/x86/kvm/vmx/hyperv.c
index b6748055c586..274fbd38c64e 100644
--- a/arch/x86/kvm/vmx/hyperv.c
+++ b/arch/x86/kvm/vmx/hyperv.c
@@ -118,8 +118,6 @@
#define EVMCS1_SUPPORTED_VMFUNC (0)
-DEFINE_STATIC_KEY_FALSE(enable_evmcs);
-
#define EVMCS1_OFFSET(x) offsetof(struct hv_enlightened_vmcs, x)
#define EVMCS1_FIELD(number, name, clean_field)[ROL16(number, 6)] = \
{EVMCS1_OFFSET(name), clean_field}
@@ -611,6 +609,8 @@ int nested_evmcs_check_controls(struct vmcs12 *vmcs12)
}
#if IS_ENABLED(CONFIG_HYPERV)
+DEFINE_STATIC_KEY_FALSE(enable_evmcs);
+
/*
* KVM on Hyper-V always uses the latest known eVMCSv1 revision, the assumption
* is: in case a feature has corresponding fields in eVMCS described and it was
diff --git a/arch/x86/kvm/vmx/hyperv.h b/arch/x86/kvm/vmx/hyperv.h
index 1299143d00df..a54a2fdf0a5b 100644
--- a/arch/x86/kvm/vmx/hyperv.h
+++ b/arch/x86/kvm/vmx/hyperv.h
@@ -16,8 +16,6 @@
struct vmcs_config;
-DECLARE_STATIC_KEY_FALSE(enable_evmcs);
-
#define current_evmcs ((struct hv_enlightened_vmcs *)this_cpu_read(current_vmcs))
#define KVM_EVMCS_VERSION 1
@@ -69,6 +67,13 @@ static inline u64 evmcs_read_any(struct hv_enlightened_vmcs *evmcs,
#if IS_ENABLED(CONFIG_HYPERV)
+DECLARE_STATIC_KEY_FALSE(enable_evmcs);
+
+static __always_inline bool kvm_is_using_evmcs(void)
+{
+ return static_branch_unlikely(&enable_evmcs);
+}
+
static __always_inline int get_evmcs_offset(unsigned long field,
u16 *clean_field)
{
@@ -158,6 +163,7 @@ static inline void evmcs_load(u64 phys_addr)
void evmcs_sanitize_exec_ctrls(struct vmcs_config *vmcs_conf);
#else /* !IS_ENABLED(CONFIG_HYPERV) */
+static __always_inline bool kvm_is_using_evmcs(void) { return false; }
static __always_inline void evmcs_write64(unsigned long field, u64 value) {}
static __always_inline void evmcs_write32(unsigned long field, u32 value) {}
static __always_inline void evmcs_write16(unsigned long field, u16 value) {}
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 33614ee2cd67..d80cbe01b5d7 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -595,7 +595,7 @@ static void hv_reset_evmcs(void)
{
struct hv_vp_assist_page *vp_ap;
- if (!static_branch_unlikely(&enable_evmcs))
+ if (!kvm_is_using_evmcs())
return;
/*
@@ -2818,8 +2818,7 @@ static int vmx_hardware_enable(void)
* This can happen if we hot-added a CPU but failed to allocate
* VP assist page for it.
*/
- if (static_branch_unlikely(&enable_evmcs) &&
- !hv_get_vp_assist_page(cpu))
+ if (kvm_is_using_evmcs() && !hv_get_vp_assist_page(cpu))
return -EFAULT;
intel_pt_handle_vmx(1);
@@ -2871,7 +2870,7 @@ struct vmcs *alloc_vmcs_cpu(bool shadow, int cpu, gfp_t flags)
memset(vmcs, 0, vmcs_config.size);
/* KVM supports Enlightened VMCS v1 only */
- if (static_branch_unlikely(&enable_evmcs))
+ if (kvm_is_using_evmcs())
vmcs->hdr.revision_id = KVM_EVMCS_VERSION;
else
vmcs->hdr.revision_id = vmcs_config.revision_id;
@@ -2966,7 +2965,7 @@ static __init int alloc_kvm_area(void)
* still be marked with revision_id reported by
* physical CPU.
*/
- if (static_branch_unlikely(&enable_evmcs))
+ if (kvm_is_using_evmcs())
vmcs->hdr.revision_id = vmcs_config.revision_id;
per_cpu(vmxarea, cpu) = vmcs;
@@ -3936,7 +3935,7 @@ static void vmx_msr_bitmap_l01_changed(struct vcpu_vmx *vmx)
* 'Enlightened MSR Bitmap' feature L0 needs to know that MSR
* bitmap has changed.
*/
- if (IS_ENABLED(CONFIG_HYPERV) && static_branch_unlikely(&enable_evmcs)) {
+ if (kvm_is_using_evmcs()) {
struct hv_enlightened_vmcs *evmcs = (void *)vmx->vmcs01.vmcs;
if (evmcs->hv_enlightenments_control.msr_bitmap)
@@ -7313,7 +7312,7 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu)
vmx_vcpu_enter_exit(vcpu, __vmx_vcpu_run_flags(vmx));
/* All fields are clean at this point */
- if (static_branch_unlikely(&enable_evmcs)) {
+ if (kvm_is_using_evmcs()) {
current_evmcs->hv_clean_fields |=
HV_VMX_ENLIGHTENED_CLEAN_FIELD_ALL;
@@ -7443,7 +7442,7 @@ static int vmx_vcpu_create(struct kvm_vcpu *vcpu)
* feature only for vmcs01, KVM currently isn't equipped to realize any
* performance benefits from enabling it for vmcs02.
*/
- if (IS_ENABLED(CONFIG_HYPERV) && static_branch_unlikely(&enable_evmcs) &&
+ if (kvm_is_using_evmcs() &&
(ms_hyperv.nested_features & HV_X64_NESTED_MSR_BITMAP)) {
struct hv_enlightened_vmcs *evmcs = (void *)vmx->vmcs01.vmcs;
diff --git a/arch/x86/kvm/vmx/vmx_ops.h b/arch/x86/kvm/vmx/vmx_ops.h
index db95bde52998..ce47dc265f89 100644
--- a/arch/x86/kvm/vmx/vmx_ops.h
+++ b/arch/x86/kvm/vmx/vmx_ops.h
@@ -147,7 +147,7 @@ static __always_inline unsigned long __vmcs_readl(unsigned long field)
static __always_inline u16 vmcs_read16(unsigned long field)
{
vmcs_check16(field);
- if (static_branch_unlikely(&enable_evmcs))
+ if (kvm_is_using_evmcs())
return evmcs_read16(field);
return __vmcs_readl(field);
}
@@ -155,7 +155,7 @@ static __always_inline u16 vmcs_read16(unsigned long field)
static __always_inline u32 vmcs_read32(unsigned long field)
{
vmcs_check32(field);
- if (static_branch_unlikely(&enable_evmcs))
+ if (kvm_is_using_evmcs())
return evmcs_read32(field);
return __vmcs_readl(field);
}
@@ -163,7 +163,7 @@ static __always_inline u32 vmcs_read32(unsigned long field)
static __always_inline u64 vmcs_read64(unsigned long field)
{
vmcs_check64(field);
- if (static_branch_unlikely(&enable_evmcs))
+ if (kvm_is_using_evmcs())
return evmcs_read64(field);
#ifdef CONFIG_X86_64
return __vmcs_readl(field);
@@ -175,7 +175,7 @@ static __always_inline u64 vmcs_read64(unsigned long field)
static __always_inline unsigned long vmcs_readl(unsigned long field)
{
vmcs_checkl(field);
- if (static_branch_unlikely(&enable_evmcs))
+ if (kvm_is_using_evmcs())
return evmcs_read64(field);
return __vmcs_readl(field);
}
@@ -222,7 +222,7 @@ static __always_inline void __vmcs_writel(unsigned long field, unsigned long val
static __always_inline void vmcs_write16(unsigned long field, u16 value)
{
vmcs_check16(field);
- if (static_branch_unlikely(&enable_evmcs))
+ if (kvm_is_using_evmcs())
return evmcs_write16(field, value);
__vmcs_writel(field, value);
@@ -231,7 +231,7 @@ static __always_inline void vmcs_write16(unsigned long field, u16 value)
static __always_inline void vmcs_write32(unsigned long field, u32 value)
{
vmcs_check32(field);
- if (static_branch_unlikely(&enable_evmcs))
+ if (kvm_is_using_evmcs())
return evmcs_write32(field, value);
__vmcs_writel(field, value);
@@ -240,7 +240,7 @@ static __always_inline void vmcs_write32(unsigned long field, u32 value)
static __always_inline void vmcs_write64(unsigned long field, u64 value)
{
vmcs_check64(field);
- if (static_branch_unlikely(&enable_evmcs))
+ if (kvm_is_using_evmcs())
return evmcs_write64(field, value);
__vmcs_writel(field, value);
@@ -252,7 +252,7 @@ static __always_inline void vmcs_write64(unsigned long field, u64 value)
static __always_inline void vmcs_writel(unsigned long field, unsigned long value)
{
vmcs_checkl(field);
- if (static_branch_unlikely(&enable_evmcs))
+ if (kvm_is_using_evmcs())
return evmcs_write64(field, value);
__vmcs_writel(field, value);
@@ -262,7 +262,7 @@ static __always_inline void vmcs_clear_bits(unsigned long field, u32 mask)
{
BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6000) == 0x2000,
"vmcs_clear_bits does not support 64-bit fields");
- if (static_branch_unlikely(&enable_evmcs))
+ if (kvm_is_using_evmcs())
return evmcs_write32(field, evmcs_read32(field) & ~mask);
__vmcs_writel(field, __vmcs_readl(field) & ~mask);
@@ -272,7 +272,7 @@ static __always_inline void vmcs_set_bits(unsigned long field, u32 mask)
{
BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6000) == 0x2000,
"vmcs_set_bits does not support 64-bit fields");
- if (static_branch_unlikely(&enable_evmcs))
+ if (kvm_is_using_evmcs())
return evmcs_write32(field, evmcs_read32(field) | mask);
__vmcs_writel(field, __vmcs_readl(field) | mask);
@@ -289,7 +289,7 @@ static inline void vmcs_load(struct vmcs *vmcs)
{
u64 phys_addr = __pa(vmcs);
- if (static_branch_unlikely(&enable_evmcs))
+ if (kvm_is_using_evmcs())
return evmcs_load(phys_addr);
vmx_asm1(vmptrld, "m"(phys_addr), vmcs, phys_addr);
--
2.39.1.581.gbfd45094c4-goog
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