Ah, here you add emulation of these bits.
On Tue, Sep 02, 2014 at 05:13:48PM +0200, Paolo Bonzini wrote:
> This is similar to what the EPT code does with the exit qualification.
> This allows the guest to see a valid value for bits 33:32.
>
> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
> ---
> arch/x86/kvm/paging_tmpl.h | 6 ++++++
> arch/x86/kvm/svm.c | 26 ++++++++++++++++++++++----
> 2 files changed, 28 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
> index 410776528265..99d4c4e836a0 100644
> --- a/arch/x86/kvm/paging_tmpl.h
> +++ b/arch/x86/kvm/paging_tmpl.h
> @@ -322,8 +322,14 @@ retry_walk:
>
> real_gfn = mmu->translate_gpa(vcpu, gfn_to_gpa(table_gfn),
> PFERR_USER_MASK|PFERR_WRITE_MASK);
> +
> + /*
> + * Can this happen (except if the guest is playing TOCTTOU
> games)?
> + * We should have gotten a nested page fault on table_gfn
> instead.
> + */
Comment is true, but doesn't make the check below obsolete, no?
> if (unlikely(real_gfn == UNMAPPED_GVA))
> goto error;
> @@ -1974,10 +1974,28 @@ static void nested_svm_inject_npf_exit(struct
> kvm_vcpu *vcpu,
> {
> struct vcpu_svm *svm = to_svm(vcpu);
>
> - svm->vmcb->control.exit_code = SVM_EXIT_NPF;
> - svm->vmcb->control.exit_code_hi = 0;
> - svm->vmcb->control.exit_info_1 = fault->error_code;
> - svm->vmcb->control.exit_info_2 = fault->address;
> + /*
> + * We can keep the value that the processor stored in the VMCB,
> + * but make up something sensible if we hit the WARN.
> + */
> + if (WARN_ON(svm->vmcb->control.exit_code != SVM_EXIT_NPF)) {
> + svm->vmcb->control.exit_code = SVM_EXIT_NPF;
> + svm->vmcb->control.exit_code_hi = 0;
> + svm->vmcb->control.exit_info_1 = (1ULL << 32);
> + svm->vmcb->control.exit_info_2 = fault->address;
> + }
Its been a while since I looked into this, but is an injected NPF exit
always the result of a real NPF exit? How about an io-port emulated on
L1 but passed through to L2 by the nested hypervisor. On emulation of
INS or OUTS, KVM would need to read/write to an L2 address space, maybe
causing NPF faults to be injected. In this case an IOIO exit would cause
an injected NPF exit for L1.
Joerg
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