Re: [PATCH 08/21] KVM: TDX: Set gfn_direct_bits to shared bit

[Paolo Bonzini]

On 9/4/24 05:07, Rick Edgecombe wrote:
> From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
>
> Make the direct root handle memslot GFNs at an alias with the TDX shared
> bit set.
>
> For TDX shared memory, the memslot GFNs need to be mapped at an alias with
> the shared bit set. These shared mappings will be be mapped on the KVM
> MMU's "direct" root. The direct root has it's mappings shifted by
> applying "gfn_direct_bits" as a mask. The concept of "GPAW" (guest
> physical address width) determines the location of the shared bit. So set
> gfn_direct_bits based on this, to map shared memory at the proper GPA.
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
> ---
> TDX MMU part 2 v1:
>   - Move setting of gfn_direct_bits to separate patch (Yan)
> ---
>   arch/x86/kvm/vmx/tdx.c | 5 +++++
>   1 file changed, 5 insertions(+)
>
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index 8f43977ef4c6..25c24901061b 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -921,6 +921,11 @@ static int tdx_td_init(struct kvm *kvm, struct kvm_tdx_cmd *cmd)
>   	kvm_tdx->attributes = td_params->attributes;
>   	kvm_tdx->xfam = td_params->xfam;
>   
> +	if (td_params->exec_controls & TDX_EXEC_CONTROL_MAX_GPAW)
> +		kvm->arch.gfn_direct_bits = gpa_to_gfn(BIT_ULL(51));
> +	else
> +		kvm->arch.gfn_direct_bits = gpa_to_gfn(BIT_ULL(47));
> +
>   out:
>   	/* kfree() accepts NULL. */
>   	kfree(init_vm);

Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>