linux-kernel - [PATCH 13/29] KVM: TDX: Set gfn_direct

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Message-ID: <20250226195529.2314580-14-pbonzini@redhat.com>
Date: Wed, 26 Feb 2025 14:55:13 -0500
From: Paolo Bonzini <pbonzini@...hat.com>
To: linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org
Cc: seanjc@...gle.com,
	Yan Zhao <yan.y.zhao@...el.com>,
	Rick Edgecombe <rick.p.edgecombe@...el.com>,
	Isaku Yamahata <isaku.yamahata@...el.com>
Subject: [PATCH 13/29] KVM: TDX: Set gfn_direct_bits to shared bit

From: Isaku Yamahata <isaku.yamahata@...el.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@...el.com>
Co-developed-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
Co-developed-by: Yan Zhao <yan.y.zhao@...el.com>
Signed-off-by: Yan Zhao <yan.y.zhao@...el.com>
Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>
Message-ID: <20241112073613.22100-1-yan.y.zhao@...el.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 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 ec86c97ada80..09c4d314e6f5 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -1045,6 +1045,11 @@ 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. */
-- 
2.43.5