Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:8 as permitted sender) client-ip=2620:137:e000::3:8;
From:   isaku.yamahata@intel.com
To:     kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Cc:     isaku.yamahata@intel.com, isaku.yamahata@gmail.com,
        Paolo Bonzini <pbonzini@redhat.com>, erdemaktas@google.com,
        Sean Christopherson <seanjc@google.com>,
        Sagi Shahar <sagis@google.com>,
        David Matlack <dmatlack@google.com>,
        Kai Huang <kai.huang@intel.com>,
        Zhi Wang <zhi.wang.linux@gmail.com>, chen.bo@intel.com,
        hang.yuan@intel.com, tina.zhang@intel.com,
        Xiaoyao Li <xiaoyao.li@intel.com>
Subject: [RFC PATCH v5 12/16] KVM: x86/tdp_mmu, TDX: Split a large page when 4KB page within it converted to shared
Date:   Mon, 16 Oct 2023 09:21:03 -0700
Message-Id: <3606f99cd9b083cdf44b7bfc81a524ed5ab85031.1697473009.git.isaku.yamahata@intel.com>
In-Reply-To: <cover.1697473009.git.isaku.yamahata@intel.com>
References: <cover.1697473009.git.isaku.yamahata@intel.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

From: Xiaoyao Li <xiaoyao.li@intel.com>

When mapping the shared page for TDX, it needs to zap private alias.

In the case that private page is mapped as large page (2MB), it can be
removed directly only when the whole 2MB is converted to shared.
Otherwise, it has to split 2MB page into 512 4KB page, and only remove
the pages that converted to shared.

When a present large leaf spte switches to present non-leaf spte, TDX needs
to split the corresponding SEPT page to reflect it.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
---
 arch/x86/include/asm/kvm-x86-ops.h |  1 +
 arch/x86/include/asm/kvm_host.h    |  2 ++
 arch/x86/kvm/mmu/tdp_mmu.c         | 21 ++++++++++++++++-----
 arch/x86/kvm/vmx/tdx.c             | 25 +++++++++++++++++++++++--
 arch/x86/kvm/vmx/tdx_arch.h        |  1 +
 arch/x86/kvm/vmx/tdx_ops.h         |  7 +++++++
 6 files changed, 50 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
index ba74cb7199b3..d751c8b58c45 100644
--- a/arch/x86/include/asm/kvm-x86-ops.h
+++ b/arch/x86/include/asm/kvm-x86-ops.h
@@ -103,6 +103,7 @@ KVM_X86_OP_OPTIONAL_RET0(get_mt_mask)
 KVM_X86_OP(load_mmu_pgd)
 KVM_X86_OP_OPTIONAL(link_private_spt)
 KVM_X86_OP_OPTIONAL(free_private_spt)
+KVM_X86_OP_OPTIONAL(split_private_spt)
 KVM_X86_OP_OPTIONAL(set_private_spte)
 KVM_X86_OP_OPTIONAL(remove_private_spte)
 KVM_X86_OP_OPTIONAL(zap_private_spte)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index bb2b4f8c0c57..d9ada89c0c55 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1745,6 +1745,8 @@ struct kvm_x86_ops {
 				void *private_spt);
 	int (*free_private_spt)(struct kvm *kvm, gfn_t gfn, enum pg_level level,
 				void *private_spt);
+	int (*split_private_spt)(struct kvm *kvm, gfn_t gfn, enum pg_level level,
+				  void *private_spt);
 	int (*set_private_spte)(struct kvm *kvm, gfn_t gfn, enum pg_level level,
 				 kvm_pfn_t pfn);
 	int (*remove_private_spte)(struct kvm *kvm, gfn_t gfn, enum pg_level level,
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 366f1b58af09..6828394cedec 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -647,23 +647,34 @@ static int __must_check __set_private_spte_present(struct kvm *kvm, tdp_ptep_t s
 {
 	bool was_present = is_shadow_present_pte(old_spte);
 	bool is_present = is_shadow_present_pte(new_spte);
+	bool was_leaf = was_present && is_last_spte(old_spte, level);
 	bool is_leaf = is_present && is_last_spte(new_spte, level);
 	kvm_pfn_t new_pfn = spte_to_pfn(new_spte);
+	void *private_spt;
 	int ret = 0;
 
 	lockdep_assert_held(&kvm->mmu_lock);
-	/* TDP MMU doesn't change present -> present */
-	KVM_BUG_ON(was_present, kvm);
 
 	/*
 	 * Use different call to either set up middle level
 	 * private page table, or leaf.
 	 */
-	if (is_leaf)
+	if (level > PG_LEVEL_4K && was_leaf && !is_leaf) {
+		/*
+		 * splitting large page into 4KB.
+		 * tdp_mmu_split_huage_page() => tdp_mmu_link_sp()
+		 */
+		private_spt = get_private_spt(gfn, new_spte, level);
+		KVM_BUG_ON(!private_spt, kvm);
+		ret = static_call(kvm_x86_zap_private_spte)(kvm, gfn, level);
+		kvm_flush_remote_tlbs(kvm);
+		if (!ret)
+			ret = static_call(kvm_x86_split_private_spt)(kvm, gfn,
+								     level, private_spt);
+	} else if (is_leaf)
 		ret = static_call(kvm_x86_set_private_spte)(kvm, gfn, level, new_pfn);
 	else {
-		void *private_spt = get_private_spt(gfn, new_spte, level);
-
+		private_spt = get_private_spt(gfn, new_spte, level);
 		KVM_BUG_ON(!private_spt, kvm);
 		ret = static_call(kvm_x86_link_private_spt)(kvm, gfn, level, private_spt);
 	}
diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index 2c760947ab21..1db56696ad99 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -1661,6 +1661,28 @@ static int tdx_sept_link_private_spt(struct kvm *kvm, gfn_t gfn,
 	return 0;
 }
 
+static int tdx_sept_split_private_spt(struct kvm *kvm, gfn_t gfn,
+				      enum pg_level level, void *private_spt)
+{
+	int tdx_level = pg_level_to_tdx_sept_level(level);
+	struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm);
+	gpa_t gpa = gfn_to_gpa(gfn) & KVM_HPAGE_MASK(level);
+	hpa_t hpa = __pa(private_spt);
+	struct tdx_module_args out;
+	u64 err;
+
+	/* See comment in tdx_sept_set_private_spte() */
+	err = tdh_mem_page_demote(kvm_tdx->tdr_pa, gpa, tdx_level, hpa, &out);
+	if (unlikely(err == TDX_ERROR_SEPT_BUSY))
+		return -EAGAIN;
+	if (KVM_BUG_ON(err, kvm)) {
+		pr_tdx_error(TDH_MEM_PAGE_DEMOTE, err, &out);
+		return -EIO;
+	}
+
+	return 0;
+}
+
 static int tdx_sept_zap_private_spte(struct kvm *kvm, gfn_t gfn,
 				      enum pg_level level)
 {
@@ -1674,8 +1696,6 @@ static int tdx_sept_zap_private_spte(struct kvm *kvm, gfn_t gfn,
 	if (unlikely(!is_hkid_assigned(kvm_tdx)))
 		return 0;
 
-	/* For now large page isn't supported yet. */
-	WARN_ON_ONCE(level != PG_LEVEL_4K);
 	err = tdh_mem_range_block(kvm_tdx->tdr_pa, gpa, tdx_level, &out);
 	if (unlikely(err == TDX_ERROR_SEPT_BUSY))
 		return -EAGAIN;
@@ -3283,6 +3303,7 @@ int __init tdx_hardware_setup(struct kvm_x86_ops *x86_ops)
 
 	x86_ops->link_private_spt = tdx_sept_link_private_spt;
 	x86_ops->free_private_spt = tdx_sept_free_private_spt;
+	x86_ops->split_private_spt = tdx_sept_split_private_spt;
 	x86_ops->set_private_spte = tdx_sept_set_private_spte;
 	x86_ops->remove_private_spte = tdx_sept_remove_private_spte;
 	x86_ops->zap_private_spte = tdx_sept_zap_private_spte;
diff --git a/arch/x86/kvm/vmx/tdx_arch.h b/arch/x86/kvm/vmx/tdx_arch.h
index 93934851610b..0c9823fcf829 100644
--- a/arch/x86/kvm/vmx/tdx_arch.h
+++ b/arch/x86/kvm/vmx/tdx_arch.h
@@ -21,6 +21,7 @@
 #define TDH_MNG_CREATE			9
 #define TDH_VP_CREATE			10
 #define TDH_MNG_RD			11
+#define TDH_MEM_PAGE_DEMOTE		15
 #define TDH_MR_EXTEND			16
 #define TDH_MR_FINALIZE			17
 #define TDH_VP_FLUSH			18
diff --git a/arch/x86/kvm/vmx/tdx_ops.h b/arch/x86/kvm/vmx/tdx_ops.h
index afc85e7ffb8e..7293510fa2e5 100644
--- a/arch/x86/kvm/vmx/tdx_ops.h
+++ b/arch/x86/kvm/vmx/tdx_ops.h
@@ -183,6 +183,13 @@ static inline u64 tdh_mng_rd(hpa_t tdr, u64 field, struct tdx_module_args *out)
 	return tdx_seamcall(TDH_MNG_RD, tdr, field, 0, 0, out);
 }
 
+static inline u64 tdh_mem_page_demote(hpa_t tdr, gpa_t gpa, int level, hpa_t page,
+				      struct tdx_module_args *out)
+{
+	tdx_clflush_page(page, PG_LEVEL_4K);
+	return tdx_seamcall_sept(TDH_MEM_PAGE_DEMOTE, gpa | level, tdr, page, 0, out);
+}
+
 static inline u64 tdh_mr_extend(hpa_t tdr, gpa_t gpa,
 				struct tdx_module_args *out)
 {
-- 
2.25.1