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

[Rick Edgecombe <rick.p.edgecombe@intel.com>]

From: Isaku Yamahata <isaku.yamahata@intel.com>

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@intel.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
---
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);
-- 
2.34.1