[RFC PATCH v6 35/36] KVM: VMX: Cache MSR_IA32_VMX_MISC in vmcs_config

Sean Christopherson
2022-08-24T03:05:14Z

Like other host VMX control MSRs, MSR_IA32_VMX_MISC can be cached in
vmcs_config to avoid the need to re-read it later, e.g. from
cpu_has_vmx_intel_pt() or cpu_has_vmx_shadow_vmcs().

No (real) functional change intended.

Reviewed-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/vmx/capabilities.h | 11 +++--------
arch/x86/kvm/vmx/vmx.c | 8 +++++---
2 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kvm/vmx/capabilities.h b/arch/x86/kvm/vmx/capabilities.h
index faee1db8b0e0..87c4e46daf37 100644
--- a/arch/x86/kvm/vmx/capabilities.h
+++ b/arch/x86/kvm/vmx/capabilities.h
@@ -65,6 +65,7 @@ struct vmcs_config {
u64 cpu_based_3rd_exec_ctrl;
u32 vmexit_ctrl;
u32 vmentry_ctrl;
+ u64 misc;
struct nested_vmx_msrs nested;
};
extern struct vmcs_config vmcs_config;
@@ -225,11 +226,8 @@ static inline bool cpu_has_vmx_vmfunc(void)

static inline bool cpu_has_vmx_shadow_vmcs(void)
{
- u64 vmx_msr;
-
/* check if the cpu supports writing r/o exit information fields */
- rdmsrl(MSR_IA32_VMX_MISC, vmx_msr);
- if (!(vmx_msr & MSR_IA32_VMX_MISC_VMWRITE_SHADOW_RO_FIELDS))
+ if (!(vmcs_config.misc & MSR_IA32_VMX_MISC_VMWRITE_SHADOW_RO_FIELDS))
return false;

return vmcs_config.cpu_based_2nd_exec_ctrl &
@@ -371,10 +369,7 @@ static inline bool cpu_has_vmx_invvpid_global(void)

static inline bool cpu_has_vmx_intel_pt(void)
{
- u64 vmx_msr;
-
- rdmsrl(MSR_IA32_VMX_MISC, vmx_msr);
- return (vmx_msr & MSR_IA32_VMX_MISC_INTEL_PT) &&
+ return (vmcs_config.misc & MSR_IA32_VMX_MISC_INTEL_PT) &&
(vmcs_config.cpu_based_2nd_exec_ctrl & SECONDARY_EXEC_PT_USE_GPA) &&
(vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_IA32_RTIT_CTL);
}
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index c42b6646afa4..f3d3a546dd2a 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2551,6 +2551,7 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf,
u64 _cpu_based_3rd_exec_control = 0;
u32 _vmexit_control = 0;
u32 _vmentry_control = 0;
+ u64 misc_msr;
int i;

/*
@@ -2684,6 +2685,8 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf,
if (((vmx_msr_high >> 18) & 15) != 6)
return -EIO;

+ rdmsrl(MSR_IA32_VMX_MISC, misc_msr);
+
vmcs_conf->size = vmx_msr_high & 0x1fff;
vmcs_conf->basic_cap = vmx_msr_high & ~0x1fff;

@@ -2695,6 +2698,7 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf,
vmcs_conf->cpu_based_3rd_exec_ctrl = _cpu_based_3rd_exec_control;
vmcs_conf->vmexit_ctrl = _vmexit_control;
vmcs_conf->vmentry_ctrl = _vmentry_control;
+ vmcs_conf->misc = misc_msr;

return 0;
}
@@ -8311,11 +8315,9 @@ static __init int hardware_setup(void)

if (enable_preemption_timer) {
u64 use_timer_freq = 5000ULL * 1000 * 1000;
- u64 vmx_msr;

- rdmsrl(MSR_IA32_VMX_MISC, vmx_msr);
cpu_preemption_timer_multi =
- vmx_msr & VMX_MISC_PREEMPTION_TIMER_RATE_MASK;
+ vmcs_config.misc & VMX_MISC_PREEMPTION_TIMER_RATE_MASK;

if (tsc_khz)
use_timer_freq = (u64)tsc_khz * 1000;
--
2.37.1.595.g718a3a8f04-goog