Commit ff8071eb authored by Sean Christopherson's avatar Sean Christopherson
Browse files

KVM: VMX: Always reflect SGX EPCM #PFs back into the guest 



When handling intercepted #PFs, reflect EPCM (Enclave Page Cache Map)
violations, i.e. #PFs with the SGX flag set, back into the guest.  KVM
doesn't shadow EPCM entries (the EPCM deals only with virtual/linear
addresses), and so EPCM violation cannot be due to KVM interference,
and more importantly can't be resolved by KVM.

On pre-SGX2 hardware, EPCM violations are delivered as #GP(0) faults, but
on SGX2+ hardware, they are delivered as #PF(SGX).  Failure to account for
the SGX2 behavior could put a vCPU into an infinite loop due to KVM not
realizing the #PF is the guest's responsibility.

Take care to deliver the EPCM violation as a #GP(0) if the _guest_ CPU
model is only SGX1.

Fixes: 72add915 ("KVM: VMX: Enable SGX virtualization for SGX1, SGX2 and LC")
Cc: Kai Huang <kai.huang@intel.com>
Reviewed-by: default avatarRichard Lyu <richard.lyu@suse.com>
Reviewed-by: default avatarKai Huang <kai.huang@intel.com>
Link: https://patch.msgid.link/20251121222018.348987-1-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 9ace4753

arch/x86/kvm/vmx/vmx.c

+44 −14
Original line number Diff line number Diff line
@@ -5303,12 +5303,53 @@ static bool is_xfd_nm_fault(struct kvm_vcpu *vcpu) 
	       !kvm_is_cr0_bit_set(vcpu, X86_CR0_TS);

}



static int vmx_handle_page_fault(struct kvm_vcpu *vcpu, u32 error_code)

{

	unsigned long cr2 = vmx_get_exit_qual(vcpu);



	if (vcpu->arch.apf.host_apf_flags)

		goto handle_pf;



	/* When using EPT, KVM intercepts #PF only to detect illegal GPAs. */

	WARN_ON_ONCE(enable_ept && !allow_smaller_maxphyaddr);



	/*

	 * On SGX2 hardware, EPCM violations are delivered as #PF with the SGX

	 * flag set in the error code (SGX1 hardware generates #GP(0)).  EPCM

	 * violations have nothing to do with shadow paging and can never be

	 * resolved by KVM; always reflect them into the guest.

	 */

	if (error_code & PFERR_SGX_MASK) {

		WARN_ON_ONCE(!IS_ENABLED(CONFIG_X86_SGX_KVM) ||

			     !cpu_feature_enabled(X86_FEATURE_SGX2));



		if (guest_cpu_cap_has(vcpu, X86_FEATURE_SGX2))

			kvm_fixup_and_inject_pf_error(vcpu, cr2, error_code);

		else

			kvm_inject_gp(vcpu, 0);

		return 1;

	}



	/*

	 * If EPT is enabled, fixup and inject the #PF.  KVM intercepts #PFs

	 * only to set PFERR_RSVD as appropriate (hardware won't set RSVD due

	 * to the GPA being legal with respect to host.MAXPHYADDR).

	 */

	if (enable_ept) {

		kvm_fixup_and_inject_pf_error(vcpu, cr2, error_code);

		return 1;

	}



handle_pf:

	return kvm_handle_page_fault(vcpu, error_code, cr2, NULL, 0);

}



static int handle_exception_nmi(struct kvm_vcpu *vcpu)

{

	struct vcpu_vmx *vmx = to_vmx(vcpu);

	struct kvm_run *kvm_run = vcpu->run;

	u32 intr_info, ex_no, error_code;

	unsigned long cr2, dr6;

	unsigned long dr6;

	u32 vect_info;



	vect_info = vmx->idt_vectoring_info;
@@ -5383,19 +5424,8 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu) 
		return 0;

	}



	if (is_page_fault(intr_info)) {

		cr2 = vmx_get_exit_qual(vcpu);

		if (enable_ept && !vcpu->arch.apf.host_apf_flags) {

			/*

			 * EPT will cause page fault only if we need to

			 * detect illegal GPAs.

			 */

			WARN_ON_ONCE(!allow_smaller_maxphyaddr);

			kvm_fixup_and_inject_pf_error(vcpu, cr2, error_code);

			return 1;

		} else

			return kvm_handle_page_fault(vcpu, error_code, cr2, NULL, 0);

	}

	if (is_page_fault(intr_info))

		return vmx_handle_page_fault(vcpu, error_code);



	ex_no = intr_info & INTR_INFO_VECTOR_MASK;