linux-kernel - [PATCH v4 05/18] KVM: x86/mmu: Add an is_mirror member for union kvm_mmu_page

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Message-Id: <20240718211230.1492011-6-rick.p.edgecombe@intel.com>
Date: Thu, 18 Jul 2024 14:12:17 -0700
From: Rick Edgecombe <rick.p.edgecombe@...el.com>
To: seanjc@...gle.com,
	pbonzini@...hat.com,
	kvm@...r.kernel.org
Cc: kai.huang@...el.com,
	dmatlack@...gle.com,
	erdemaktas@...gle.com,
	isaku.yamahata@...il.com,
	linux-kernel@...r.kernel.org,
	sagis@...gle.com,
	yan.y.zhao@...el.com,
	rick.p.edgecombe@...el.com,
	Isaku Yamahata <isaku.yamahata@...el.com>
Subject: [PATCH v4 05/18] KVM: x86/mmu: Add an is_mirror member for union kvm_mmu_page_role

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

Introduce a "is_mirror" member to the kvm_mmu_page_role union to identify
SPTEs associated with the mirrored EPT.

The TDX module maintains the private half of the EPT mapped in the TD in
its protected memory. KVM keeps a copy of the private GPAs in a mirrored
EPT tree within host memory. This "is_mirror" attribute enables vCPUs to
find and get the root page of mirrored EPT from the MMU root list for a
guest TD. This also allows KVM MMU code to detect changes in mirrored EPT
according to the "is_mirror" mmu page role and propagate the changes to
the private EPT managed by TDX module.

Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
---
v3:
 - Rename role mirror_pt -> is_mirror (Paolo)
 - Remove unnessary helpers that just access a member (Paolo)

v2:
 - Rename private -> mirrored

v1:
- Remove warning and NULL check in is_private_sptep() (Rick)
- Update commit log (Yan)
---
 arch/x86/include/asm/kvm_host.h | 3 ++-
 arch/x86/kvm/mmu/mmu_internal.h | 5 +++++
 arch/x86/kvm/mmu/spte.h         | 5 +++++
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 09aa2c56bab6..f764a07a32f9 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -351,7 +351,8 @@ union kvm_mmu_page_role {
 		unsigned ad_disabled:1;
 		unsigned guest_mode:1;
 		unsigned passthrough:1;
-		unsigned :5;
+		unsigned is_mirror:1;
+		unsigned :4;
 
 		/*
 		 * This is left at the top of the word so that
diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
index 68f99d9d6e7c..3319d0a42f36 100644
--- a/arch/x86/kvm/mmu/mmu_internal.h
+++ b/arch/x86/kvm/mmu/mmu_internal.h
@@ -157,6 +157,11 @@ static inline int kvm_mmu_page_as_id(struct kvm_mmu_page *sp)
 	return kvm_mmu_role_as_id(sp->role);
 }
 
+static inline bool is_mirror_sp(const struct kvm_mmu_page *sp)
+{
+	return sp->role.is_mirror;
+}
+
 static inline void kvm_mmu_alloc_external_spt(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
 {
 	/*
diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h
index ef793c459b05..a72f0e3bde17 100644
--- a/arch/x86/kvm/mmu/spte.h
+++ b/arch/x86/kvm/mmu/spte.h
@@ -267,6 +267,11 @@ static inline struct kvm_mmu_page *root_to_sp(hpa_t root)
 	return spte_to_child_sp(root);
 }
 
+static inline bool is_mirror_sptep(u64 *sptep)
+{
+	return is_mirror_sp(sptep_to_sp(sptep));
+}
+
 static inline bool is_mmio_spte(struct kvm *kvm, u64 spte)
 {
 	return (spte & shadow_mmio_mask) == kvm->arch.shadow_mmio_value &&
-- 
2.34.1