linux-kernel - [PATCH v2 04/15] KVM: x86/mmu: Add a new mirror_pt member for union kvm_mmu_page

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Message-Id: <20240530210714.364118-5-rick.p.edgecombe@intel.com>
Date: Thu, 30 May 2024 14:07:03 -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 v2 04/15] KVM: x86/mmu: Add a new mirror_pt member for union kvm_mmu_page_role

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

Introduce a "mirror_pt" 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 "mirror_pt" 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 "mirror_pt" 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>
---
TDX MMU Prep v2:
 - Rename private -> mirrored

TDX MMU Prep:
- Remove warning and NULL check in is_private_sptep() (Rick)
- Update commit log (Yan)

v19:
- Fix is_private_sptep() when NULL case.
- drop CONFIG_KVM_MMU_PRIVATE
---
 arch/x86/include/asm/kvm_host.h | 13 ++++++++++++-
 arch/x86/kvm/mmu/mmu_internal.h |  5 +++++
 arch/x86/kvm/mmu/spte.h         |  5 +++++
 3 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 250899a0239b..084f4708aff1 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 mirror_pt:1;
+		unsigned :4;
 
 		/*
 		 * This is left at the top of the word so that
@@ -363,6 +364,16 @@ union kvm_mmu_page_role {
 	};
 };
 
+static inline bool kvm_mmu_page_role_is_mirror(union kvm_mmu_page_role role)
+{
+	return !!role.mirror_pt;
+}
+
+static inline void kvm_mmu_page_role_set_mirrored(union kvm_mmu_page_role *role)
+{
+	role->mirror_pt = 1;
+}
+
 /*
  * kvm_mmu_extended_role complements kvm_mmu_page_role, tracking properties
  * relevant to the current MMU configuration.   When loading CR0, CR4, or EFER,
diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
index faef40a561f9..6d82e389cd65 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 kvm_mmu_page_role_is_mirror(sp->role);
+}
+
 static inline void *kvm_mmu_mirrored_spt(struct kvm_mmu_page *sp)
 {
 	return sp->mirrored_spt;
diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h
index 5dd5405fa07a..b3c065280ba1 100644
--- a/arch/x86/kvm/mmu/spte.h
+++ b/arch/x86/kvm/mmu/spte.h
@@ -265,6 +265,11 @@ 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