[PATCH v9 10/27] KVM: x86: Refine xsave-managed guest register/MSR reset handling

Yang Weijiang
2024-01-24T02:42:39Z

Tweak the code a bit to facilitate resetting more xstate components in
the future, e.g., adding CET's xstate-managed MSRs.

No functional change intended.

Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
---
arch/x86/kvm/x86.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0e7dc3398293..3671f4868d1b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -12205,6 +12205,11 @@ void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
static_branch_dec(&kvm_has_noapic_vcpu);
}

+static inline bool is_xstate_reset_needed(void)
+{
+ return kvm_cpu_cap_has(X86_FEATURE_MPX);
+}
+
void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
{
struct kvm_cpuid_entry2 *cpuid_0x1;
@@ -12262,7 +12267,7 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
kvm_async_pf_hash_reset(vcpu);
vcpu->arch.apf.halted = false;

- if (vcpu->arch.guest_fpu.fpstate && kvm_mpx_supported()) {
+ if (vcpu->arch.guest_fpu.fpstate && is_xstate_reset_needed()) {
struct fpstate *fpstate = vcpu->arch.guest_fpu.fpstate;

/*
@@ -12272,8 +12277,12 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
if (init_event)
kvm_put_guest_fpu(vcpu);

- fpstate_clear_xstate_component(fpstate, XFEATURE_BNDREGS);
- fpstate_clear_xstate_component(fpstate, XFEATURE_BNDCSR);
+ if (kvm_cpu_cap_has(X86_FEATURE_MPX)) {
+ fpstate_clear_xstate_component(fpstate,
+ XFEATURE_BNDREGS);
+ fpstate_clear_xstate_component(fpstate,
+ XFEATURE_BNDCSR);
+ }

if (init_event)
kvm_load_guest_fpu(vcpu);
--
2.39.3