Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | Date | Tue, 6 Jun 2023 12:20:03 +0800 | Subject | Re: [PATCH v1 5/6] KVM: x86: LASS protection on KVM emulation | From | Binbin Wu <> |
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On 6/1/2023 10:23 PM, Zeng Guang wrote: > Do LASS violation check for instructions emulated by KVM. Note that for > instructions executed in the guest directly, hardware will perform the > check. > > Not all instruction emulation leads to accesses to guest linear addresses > because 1) some instructions like CPUID, RDMSR, don't take memory as > operands 2) instruction fetch in most cases is already done inside the > guest. > > Four cases in which KVM uses a linear address to access guest memory: > - KVM emulates instruction fetches or data accesses > - KVM emulates implicit data access to a system data structure > - VMX instruction emulation > - SGX ENCLS instruction emulation > > LASS violation check applies to these linear addresses so as to enforce > mode-based protections as hardware behaves. > > As exceptions, the target memory address of emulation of invlpg, branch > and call instructions doesn't require LASS violation check. I think LASS doesn't apply to the target addresses in the descriptors of INVPCID and INVVPID. Although no code change needed, IMHO, it's better to describe it in the changelog or/and comments.
> > Signed-off-by: Zeng Guang <guang.zeng@intel.com> > Tested-by: Xuelian Guo <xuelian.guo@intel.com> > --- > arch/x86/kvm/emulate.c | 30 ++++++++++++++++++++++++++++-- > arch/x86/kvm/vmx/nested.c | 3 +++ > arch/x86/kvm/vmx/sgx.c | 4 ++++ > 3 files changed, 35 insertions(+), 2 deletions(-) > [...] > diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c > index e35cf0bd0df9..bb1c3fa13c13 100644 > --- a/arch/x86/kvm/vmx/nested.c > +++ b/arch/x86/kvm/vmx/nested.c > @@ -4986,6 +4986,9 @@ int get_vmx_mem_address(struct kvm_vcpu *vcpu, unsigned long exit_qualification, > * destination for long mode! > */ > exn = is_noncanonical_address(*ret, vcpu); > + > + if (!exn) > + exn = vmx_check_lass(vcpu, 0, *ret, 0); Can be simpler by using logical-or:
exn = is_noncanonical_address(*ret, vcpu) || vmx_check_lass(vcpu, 0, *ret, 0);
> } else { > /* > * When not in long mode, the virtual/linear address is > diff --git a/arch/x86/kvm/vmx/sgx.c b/arch/x86/kvm/vmx/sgx.c > index 2261b684a7d4..3825275827eb 100644 > --- a/arch/x86/kvm/vmx/sgx.c > +++ b/arch/x86/kvm/vmx/sgx.c > @@ -46,6 +46,10 @@ static int sgx_get_encls_gva(struct kvm_vcpu *vcpu, unsigned long offset, > ((s.base != 0 || s.limit != 0xffffffff) && > (((u64)*gva + size - 1) > s.limit + 1)); > } > + > + if (!fault && is_long_mode(vcpu)) > + fault = vmx_check_lass(vcpu, 0, *gva, 0); > + > if (fault) > kvm_inject_gp(vcpu, 0); > return fault ? -EINVAL : 0;
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