From: Chao Gao Date: Tue, 12 Aug 2025 02:55:13 +0000 (-0700) Subject: KVM: x86: Zero XSTATE components on INIT by iterating over supported features X-Git-Tag: v6.18-rc1~55^2~6^2~21 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=c26675447faff8c4ddc1dc5d2cd28326b8181aaf;p=thirdparty%2Fkernel%2Flinux.git KVM: x86: Zero XSTATE components on INIT by iterating over supported features Tweak the code a bit to facilitate resetting more xstate components in the future, e.g., CET's xstate-managed MSRs. No functional change intended. Suggested-by: Sean Christopherson Tested-by: Mathias Krause Tested-by: John Allen Signed-off-by: Chao Gao Tested-by: Rick Edgecombe Link: https://lore.kernel.org/r/20250812025606.74625-6-chao.gao@intel.com Signed-off-by: Sean Christopherson --- diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index d398ee84c8f3e..8bfba7d8f7509 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -12401,6 +12401,8 @@ void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu) static void kvm_xstate_reset(struct kvm_vcpu *vcpu, bool init_event) { struct fpstate *fpstate = vcpu->arch.guest_fpu.fpstate; + u64 xfeatures_mask; + int i; /* * Guest FPU state is zero allocated and so doesn't need to be manually @@ -12414,16 +12416,20 @@ static void kvm_xstate_reset(struct kvm_vcpu *vcpu, bool init_event) * are unchanged. Currently, the only components that are zeroed and * supported by KVM are MPX related. */ - if (!kvm_mpx_supported()) + xfeatures_mask = (kvm_caps.supported_xcr0 | kvm_caps.supported_xss) & + (XFEATURE_MASK_BNDREGS | XFEATURE_MASK_BNDCSR); + if (!xfeatures_mask) return; + BUILD_BUG_ON(sizeof(xfeatures_mask) * BITS_PER_BYTE <= XFEATURE_MAX); + /* * All paths that lead to INIT are required to load the guest's FPU * state (because most paths are buried in KVM_RUN). */ kvm_put_guest_fpu(vcpu); - fpstate_clear_xstate_component(fpstate, XFEATURE_BNDREGS); - fpstate_clear_xstate_component(fpstate, XFEATURE_BNDCSR); + for_each_set_bit(i, (unsigned long *)&xfeatures_mask, XFEATURE_MAX) + fpstate_clear_xstate_component(fpstate, i); kvm_load_guest_fpu(vcpu); }