Re: [PATCH 1/5] KVM: x86: Add function to inject guest page fault with reserved bits set

[Sean Christopherson]

On Thu, Feb 27, 2020 at 07:23:02PM +0200, Mohammed Gamal wrote:
> Signed-off-by: Mohammed Gamal <mgamal@xxxxxxxxxx>
> ---
>  arch/x86/kvm/x86.c | 14 ++++++++++++++
>  arch/x86/kvm/x86.h |  1 +
>  2 files changed, 15 insertions(+)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 359fcd395132..434c55a8b719 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -10494,6 +10494,20 @@ u64 kvm_spec_ctrl_valid_bits(struct kvm_vcpu *vcpu)
>  }
>  EXPORT_SYMBOL_GPL(kvm_spec_ctrl_valid_bits);
>  
> +void kvm_inject_rsvd_bits_pf(struct kvm_vcpu *vcpu, gpa_t gpa)
> +{
> +	struct x86_exception fault;
> +
> +	fault.vector = PF_VECTOR;
> +	fault.error_code_valid = true;
> +	fault.error_code = PFERR_RSVD_MASK;

As Jim pointed out, by definition this is PRESENT.  Other bits needs to
be translated from the VMCS.EXIT_QUALIFICATION field and/or manually
calculated for EPT.  I assume NPT is more or less good to go, i.e. just
pass in the error_code?

> +	fault.nested_page_fault = false;
> +	fault.address = gpa;

Taking the GPA is wrong, @address is CR3, a GVA.

> +	kvm_inject_page_fault(vcpu, &fault);

This needs to be

	vcpu->arch.walk_mmu->inject_page_fault(vcpu, &fault);

so that L1 (nested VMX) can intercept the #PF.

> +}
> +EXPORT_SYMBOL_GPL(kvm_inject_rsvd_bits_pf);
> +
>  EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_exit);
>  EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_fast_mmio);
>  EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_inj_virq);
> diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
> index 3624665acee4..7d8ab28a6983 100644
> --- a/arch/x86/kvm/x86.h
> +++ b/arch/x86/kvm/x86.h
> @@ -276,6 +276,7 @@ int kvm_mtrr_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata);
>  bool kvm_mtrr_check_gfn_range_consistency(struct kvm_vcpu *vcpu, gfn_t gfn,
>  					  int page_num);
>  bool kvm_vector_hashing_enabled(void);
> +void kvm_inject_rsvd_bits_pf(struct kvm_vcpu *vcpu, gpa_t gpa);
>  int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
>  			    int emulation_type, void *insn, int insn_len);
>  enum exit_fastpath_completion handle_fastpath_set_msr_irqoff(struct kvm_vcpu *vcpu);
> -- 
> 2.21.1
>