Re: [RFC PATCH v3 23/27] KVM: VMX: Add SGX ENCLS[ECREATE] handler to enforce CPUID restrictions

Sean Christopherson
2021-02-03T01:37:02Z

On Wed, Feb 03, 2021, Edgecombe, Rick P wrote:
> On Tue, 2021-01-26 at 22:31 +1300, Kai Huang wrote:
> > +static int handle_encls_ecreate(struct kvm_vcpu *vcpu)
> > +{
> > +       unsigned long a_hva, m_hva, x_hva, s_hva, secs_hva;
> > +       struct kvm_cpuid_entry2 *sgx_12_0, *sgx_12_1;
> > +       gpa_t metadata_gpa, contents_gpa, secs_gpa;
> > +       struct sgx_pageinfo pageinfo;
> > +       gva_t pageinfo_gva, secs_gva;
> > +       u64 attributes, xfrm, size;
> > +       struct x86_exception ex;
> > +       u8 max_size_log2;
> > +       u32 miscselect;
> > +       int trapnr, r;
> > +
> > +       sgx_12_0 = kvm_find_cpuid_entry(vcpu, 0x12, 0);
> > +       sgx_12_1 = kvm_find_cpuid_entry(vcpu, 0x12, 1);
> > +       if (!sgx_12_0 || !sgx_12_1) {
> > +               kvm_inject_gp(vcpu, 0);
> > +               return 1;
> > +       }
> > +
> > +       if (sgx_get_encls_gva(vcpu, kvm_rbx_read(vcpu), 32, 32,
> > &pageinfo_gva) ||
> > +           sgx_get_encls_gva(vcpu, kvm_rcx_read(vcpu), 4096, 4096,
> > &secs_gva))
> > +               return 1;
> > +
> > +       /*
> > +        * Copy the PAGEINFO to local memory, its pointers need to be
> > +        * translated, i.e. we need to do a deep copy/translate.
> > +        */
> > +       r = kvm_read_guest_virt(vcpu, pageinfo_gva, &pageinfo,
> > +                               sizeof(pageinfo), &ex);
> > +       if (r == X86EMUL_PROPAGATE_FAULT) {
> > +               kvm_inject_emulated_page_fault(vcpu, &ex);
> > +               return 1;
> > +       } else if (r != X86EMUL_CONTINUE) {
> > +               sgx_handle_emulation_failure(vcpu, pageinfo_gva,
> > size);
> > +               return 0;
> > +       }
> > +
> > +       /*
> > +        * Verify alignment early.  This conveniently avoids having
> > to worry
> > +        * about page splits on userspace addresses.
> > +        */
> > +       if (!IS_ALIGNED(pageinfo.metadata, 64) ||
> > +           !IS_ALIGNED(pageinfo.contents, 4096)) {
> > +               kvm_inject_gp(vcpu, 0);
> > +               return 1;
> > +       }
> > +
> > +       /*
> > +        * Translate the SECINFO, SOURCE and SECS pointers from GVA
> > to GPA.
> > +        * Resume the guest on failure to inject a #PF.
> > +        */
> > +       if (sgx_gva_to_gpa(vcpu, pageinfo.metadata, false,
> > &metadata_gpa) ||
> > +           sgx_gva_to_gpa(vcpu, pageinfo.contents, false,
> > &contents_gpa) ||
> > +           sgx_gva_to_gpa(vcpu, secs_gva, true, &secs_gpa))
> > +               return 1;
> > +
>
> Do pageinfo.metadata and pageinfo.contents need cannonical checks here?

Bugger, yes. So much boilerplate needed in this code :-/

Maybe add yet another helper to do alignment+canonical checks, up where the
IS_ALIGNED() calls are?