Re: [RFC PATCH v2 16/26] KVM: x86: Export kvm_mmu_gva_to_gpa_{read,write}() for SGX (VMX)

[Jarkko Sakkinen <jarkko@kernel.org>]

On Mon, Jan 18, 2021 at 04:28:27PM +1300, Kai Huang wrote:
> From: Sean Christopherson <sean.j.christopherson@intel.com>
> 
> Export the gva_to_gpa() helpers for use by SGX virtualization when
> executing ENCLS[ECREATE] and ENCLS[EINIT] on behalf of the guest.
> To execute ECREATE and EINIT, KVM must obtain the GPA of the target
> Secure Enclave Control Structure (SECS) in order to get its
> corresponding HVA.
> 
> Because the SECS must reside in the Enclave Page Cache (EPC), copying
> the SECS's data to a host-controlled buffer via existing exported
> helpers is not a viable option as the EPC is not readable or writable
> by the kernel.
> 
> SGX virtualization will also use gva_to_gpa() to obtain HVAs for
> non-EPC pages in order to pass user pointers directly to ECREATE and
> EINIT, which avoids having to copy pages worth of data into the kernel.
> 
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> Signed-off-by: Kai Huang <kai.huang@intel.com>

Acked-by: Jarkko Sakkinen <jarkko@kernel.org>

/Jarkko

> ---
>  arch/x86/kvm/x86.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 9a8969a6dd06..5ca7b181a3ae 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -5891,6 +5891,7 @@ gpa_t kvm_mmu_gva_to_gpa_read(struct kvm_vcpu *vcpu, gva_t gva,
>  	u32 access = (kvm_x86_ops.get_cpl(vcpu) == 3) ? PFERR_USER_MASK : 0;
>  	return vcpu->arch.walk_mmu->gva_to_gpa(vcpu, gva, access, exception);
>  }
> +EXPORT_SYMBOL_GPL(kvm_mmu_gva_to_gpa_read);
>  
>   gpa_t kvm_mmu_gva_to_gpa_fetch(struct kvm_vcpu *vcpu, gva_t gva,
>  				struct x86_exception *exception)
> @@ -5907,6 +5908,7 @@ gpa_t kvm_mmu_gva_to_gpa_write(struct kvm_vcpu *vcpu, gva_t gva,
>  	access |= PFERR_WRITE_MASK;
>  	return vcpu->arch.walk_mmu->gva_to_gpa(vcpu, gva, access, exception);
>  }
> +EXPORT_SYMBOL_GPL(kvm_mmu_gva_to_gpa_write);
>  
>  /* uses this to access any guest's mapped memory without checking CPL */
>  gpa_t kvm_mmu_gva_to_gpa_system(struct kvm_vcpu *vcpu, gva_t gva,
> -- 
> 2.29.2
> 
>