[PATCH v2 08/24] KVM: TDX: Set gfn_direct_bits to shared bit

Yan Zhao
2024-11-12T07:38:44Z

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 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>
Co-developed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Co-developed-by: Yan Zhao <yan.y.zhao@intel.com>
Signed-off-by: Yan Zhao <yan.y.zhao@intel.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
---
TDX MMU part 2 v2:
- Added Paolo's rb
- Use TDX 1.5 naming of config_flags instead of exec_controls (Xiaoyao)
- Use macro TDX_SHARED_BITS_PWL_5 and TDX_SHARED_BITS_PWL_4 for
gfn_direct_bits. (Yan)

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 785ee9f95504..38369cafc175 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -1041,6 +1041,11 @@ 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->config_flags & TDX_CONFIG_FLAGS_MAX_GPAW)
+ kvm->arch.gfn_direct_bits = TDX_SHARED_BIT_PWL_5;
+ else
+ kvm->arch.gfn_direct_bits = TDX_SHARED_BIT_PWL_4;
+
kvm_tdx->state = TD_STATE_INITIALIZED;
out:
/* kfree() accepts NULL. */
--
2.43.2