On 1/25/2024 6:17 PM, Chao Gao wrote:
On Tue, Jan 23, 2024 at 06:41:43PM -0800, Yang Weijiang wrote: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@xxxxxxxxx> Reviewed-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx> --- 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); + }Checking whether KVM supports MPX is indirect and adds complexity. how about something like: #define XSTATE_NEED_RESET_MASK (XFEATURE_MASK_BNDREGS | \ XFEATURE_MASK_BNDCSR) u64 reset_mask; ... reset_mask = (kvm_caps.supported_xcr0 | kvm_caps.supported_xss) & XSTATE_NEED_RESET_MASK; if (vcpu->arch.guest_fpu.fpstate && reset_mask) { ... for_each_set_bit(i, &reset_mask, XFEATURE_MAX) fpstate_clear_xstate_component(fpstate, i); ... } then in patch 24, you can simply add CET_U/S into XSTATE_NEED_RESET_MASK.
Yes, the proposal looks good to me, will apply it in next version, thanks!
