linux-kernel - [RFC PATCH 09/21] KVM: TDX: Enable 2MB mapping size after TD is RUNNABLE

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Message-ID: <20250424030618.352-1-yan.y.zhao@intel.com>
Date: Thu, 24 Apr 2025 11:06:18 +0800
From: Yan Zhao <yan.y.zhao@...el.com>
To: pbonzini@...hat.com,
	seanjc@...gle.com
Cc: linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org,
	x86@...nel.org,
	rick.p.edgecombe@...el.com,
	dave.hansen@...el.com,
	kirill.shutemov@...el.com,
	tabba@...gle.com,
	ackerleytng@...gle.com,
	quic_eberman@...cinc.com,
	michael.roth@....com,
	david@...hat.com,
	vannapurve@...gle.com,
	vbabka@...e.cz,
	jroedel@...e.de,
	thomas.lendacky@....com,
	pgonda@...gle.com,
	zhiquan1.li@...el.com,
	fan.du@...el.com,
	jun.miao@...el.com,
	ira.weiny@...el.com,
	isaku.yamahata@...el.com,
	xiaoyao.li@...el.com,
	binbin.wu@...ux.intel.com,
	chao.p.peng@...el.com,
	Yan Zhao <yan.y.zhao@...el.com>
Subject: [RFC PATCH 09/21] KVM: TDX: Enable 2MB mapping size after TD is RUNNABLE

Allow TDX's .private_max_mapping_level hook to return 2MB after the TD is
RUNNABLE, enabling KVM to map TDX private pages at the 2MB level. Remove
TODOs and adjust KVM_BUG_ON()s accordingly.

Note: Instead of placing this patch at the tail of the series, it's
positioned here to show the code changes for basic mapping of private huge
pages (i.e., transitioning from non-present to present).

However, since this patch also allows KVM to trigger the merging of small
entries into a huge leaf entry or the splitting of a huge leaf entry into
small entries, errors are expected if any of these operations are triggered
due to the current lack of splitting/merging support.

Signed-off-by: Xiaoyao Li <xiaoyao.li@...el.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
Signed-off-by: Yan Zhao <yan.y.zhao@...el.com>
---
 arch/x86/kvm/vmx/tdx.c | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index e23dce59fc72..6b3a8f3e6c9c 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -1561,10 +1561,6 @@ int tdx_sept_set_private_spte(struct kvm *kvm, gfn_t gfn,
 	struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm);
 	struct page *page = pfn_to_page(pfn);
 
-	/* TODO: handle large pages. */
-	if (KVM_BUG_ON(level != PG_LEVEL_4K, kvm))
-		return -EINVAL;
-
 	/*
 	 * Because guest_memfd doesn't support page migration with
 	 * a_ops->migrate_folio (yet), no callback is triggered for KVM on page
@@ -1612,8 +1608,7 @@ static int tdx_sept_drop_private_spte(struct kvm *kvm, gfn_t gfn,
 	gpa_t gpa = gfn_to_gpa(gfn);
 	u64 err, entry, level_state;
 
-	/* TODO: handle large pages. */
-	if (KVM_BUG_ON(level != PG_LEVEL_4K, kvm))
+	if (KVM_BUG_ON(kvm_tdx->state != TD_STATE_RUNNABLE && level != PG_LEVEL_4K, kvm))
 		return -EINVAL;
 
 	if (KVM_BUG_ON(!is_hkid_assigned(kvm_tdx), kvm))
@@ -1714,8 +1709,8 @@ static int tdx_sept_zap_private_spte(struct kvm *kvm, gfn_t gfn,
 	gpa_t gpa = gfn_to_gpa(gfn) & KVM_HPAGE_MASK(level);
 	u64 err, entry, level_state;
 
-	/* For now large page isn't supported yet. */
-	WARN_ON_ONCE(level != PG_LEVEL_4K);
+	/* Before TD runnable, large page is not supported */
+	WARN_ON_ONCE(kvm_tdx->state != TD_STATE_RUNNABLE && level != PG_LEVEL_4K);
 
 	err = tdh_mem_range_block(&kvm_tdx->td, gpa, tdx_level, &entry, &level_state);
 
@@ -1817,6 +1812,9 @@ int tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn,
 	struct page *page = pfn_to_page(pfn);
 	int ret;
 
+	WARN_ON_ONCE(folio_page_idx(page_folio(page), page) + KVM_PAGES_PER_HPAGE(level) >
+		     folio_nr_pages(page_folio(page)));
+
 	/*
 	 * HKID is released after all private pages have been removed, and set
 	 * before any might be populated. Warn if zapping is attempted when
@@ -3265,7 +3263,7 @@ int tdx_gmem_private_max_mapping_level(struct kvm *kvm, kvm_pfn_t pfn)
 	if (unlikely(to_kvm_tdx(kvm)->state != TD_STATE_RUNNABLE))
 		return PG_LEVEL_4K;
 
-	return PG_LEVEL_4K;
+	return PG_LEVEL_2M;
 }
 
 static int tdx_online_cpu(unsigned int cpu)
-- 
2.43.2