From: Sean Christopherson seanjc@google.com
commit c33f6f2228fe8517e38941a508e9f905f99ecba9 upstream.
Split the common x86 parts of kvm_is_valid_cr4(), i.e. the reserved bits checks, into a separate helper, __kvm_is_valid_cr4(), and export only the inner helper to vendor code in order to prevent nested VMX from calling back into vmx_is_valid_cr4() via kvm_is_valid_cr4().
On SVM, this is a nop as SVM doesn't place any additional restrictions on CR4.
On VMX, this is also currently a nop, but only because nested VMX is missing checks on reserved CR4 bits for nested VM-Enter. That bug will be fixed in a future patch, and could simply use kvm_is_valid_cr4() as-is, but nVMX has _another_ bug where VMXON emulation doesn't enforce VMX's restrictions on CR0/CR4. The cleanest and most intuitive way to fix the VMXON bug is to use nested_host_cr{0,4}_valid(). If the CR4 variant routes through kvm_is_valid_cr4(), using nested_host_cr4_valid() won't do the right thing for the VMXON case as vmx_is_valid_cr4() enforces VMX's restrictions if and only if the vCPU is post-VMXON.
Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson seanjc@google.com Message-Id: 20220607213604.3346000-2-seanjc@google.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kvm/svm/nested.c | 3 ++- arch/x86/kvm/vmx/vmx.c | 4 ++-- arch/x86/kvm/x86.c | 12 +++++++++--- arch/x86/kvm/x86.h | 2 +- 4 files changed, 14 insertions(+), 7 deletions(-)
--- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -320,7 +320,8 @@ static bool __nested_vmcb_check_save(str return false; }
- if (CC(!kvm_is_valid_cr4(vcpu, save->cr4))) + /* Note, SVM doesn't have any additional restrictions on CR4. */ + if (CC(!__kvm_is_valid_cr4(vcpu, save->cr4))) return false;
if (CC(!kvm_valid_efer(vcpu, save->efer))) --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -3230,8 +3230,8 @@ static bool vmx_is_valid_cr4(struct kvm_ { /* * We operate under the default treatment of SMM, so VMX cannot be - * enabled under SMM. Note, whether or not VMXE is allowed at all is - * handled by kvm_is_valid_cr4(). + * enabled under SMM. Note, whether or not VMXE is allowed at all, + * i.e. is a reserved bit, is handled by common x86 code. */ if ((cr4 & X86_CR4_VMXE) && is_smm(vcpu)) return false; --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1094,7 +1094,7 @@ int kvm_emulate_xsetbv(struct kvm_vcpu * } EXPORT_SYMBOL_GPL(kvm_emulate_xsetbv);
-bool kvm_is_valid_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) +bool __kvm_is_valid_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) { if (cr4 & cr4_reserved_bits) return false; @@ -1102,9 +1102,15 @@ bool kvm_is_valid_cr4(struct kvm_vcpu *v if (cr4 & vcpu->arch.cr4_guest_rsvd_bits) return false;
- return static_call(kvm_x86_is_valid_cr4)(vcpu, cr4); + return true; +} +EXPORT_SYMBOL_GPL(__kvm_is_valid_cr4); + +static bool kvm_is_valid_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) +{ + return __kvm_is_valid_cr4(vcpu, cr4) && + static_call(kvm_x86_is_valid_cr4)(vcpu, cr4); } -EXPORT_SYMBOL_GPL(kvm_is_valid_cr4);
void kvm_post_set_cr4(struct kvm_vcpu *vcpu, unsigned long old_cr4, unsigned long cr4) { --- a/arch/x86/kvm/x86.h +++ b/arch/x86/kvm/x86.h @@ -407,7 +407,7 @@ static inline void kvm_machine_check(voi void kvm_load_guest_xsave_state(struct kvm_vcpu *vcpu); void kvm_load_host_xsave_state(struct kvm_vcpu *vcpu); int kvm_spec_ctrl_test_value(u64 value); -bool kvm_is_valid_cr4(struct kvm_vcpu *vcpu, unsigned long cr4); +bool __kvm_is_valid_cr4(struct kvm_vcpu *vcpu, unsigned long cr4); int kvm_handle_memory_failure(struct kvm_vcpu *vcpu, int r, struct x86_exception *e); int kvm_handle_invpcid(struct kvm_vcpu *vcpu, unsigned long type, gva_t gva);