Commit c2667544 authored by Chao Gao's avatar Chao Gao Committed by Sean Christopherson
Browse files

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: default avatarSean Christopherson <seanjc@google.com>
Tested-by: default avatarMathias Krause <minipli@grsecurity.net>
Tested-by: default avatarJohn Allen <john.allen@amd.com>
Signed-off-by: default avatarChao Gao <chao.gao@intel.com>
Tested-by: default avatarRick Edgecombe <rick.p.edgecombe@intel.com>
Link: https://lore.kernel.org/r/20250812025606.74625-6-chao.gao@intel.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 41f6710f

arch/x86/kvm/x86.c

+9 −3
Original line number Diff line number Diff line
@@ -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);

}