From c33f6f2228fe8517e38941a508e9f905f99ecba9 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Tue, 7 Jun 2022 21:35:50 +0000 Subject: KVM: x86: Split kvm_is_valid_cr4() and export only the non-vendor bits 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 Message-Id: <20220607213604.3346000-2-seanjc@google.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/svm/nested.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'arch/x86/kvm/svm/nested.c') diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index 23252ab82194..76dcc8a3e849 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -325,7 +325,8 @@ static bool __nested_vmcb_check_save(struct kvm_vcpu *vcpu, 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))) -- cgit v1.2.3