linux-kernel - [RFC PATCH v2 08/18] KVM: x86/mmu: Drop the return code from kvm_x86_ops.remove_external

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Message-ID: <20250829000618.351013-9-seanjc@google.com>
Date: Thu, 28 Aug 2025 17:06:08 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Ira Weiny <ira.weiny@...el.com>, Kai Huang <kai.huang@...el.com>, 
	Michael Roth <michael.roth@....com>, Yan Zhao <yan.y.zhao@...el.com>, 
	Vishal Annapurve <vannapurve@...gle.com>, Rick Edgecombe <rick.p.edgecombe@...el.com>, 
	Ackerley Tng <ackerleytng@...gle.com>
Subject: [RFC PATCH v2 08/18] KVM: x86/mmu: Drop the return code from kvm_x86_ops.remove_external_spte()

Drop the return code from kvm_x86_ops.remove_external_spte(), a.k.a.
tdx_sept_remove_private_spte(), as KVM simply does a KVM_BUG_ON() failure,
and that KVM_BUG_ON() is redundant since all error paths in TDX also do a
KVM_BUG_ON().

Opportunistically pass the spte instead of the pfn, as the API is clearly
about removing an spte.

Suggested-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/include/asm/kvm_host.h |  4 ++--
 arch/x86/kvm/mmu/tdp_mmu.c      |  8 ++------
 arch/x86/kvm/vmx/tdx.c          | 17 ++++++++---------
 3 files changed, 12 insertions(+), 17 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 0d3cc0fc27af..d0a8404a6b8f 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1852,8 +1852,8 @@ struct kvm_x86_ops {
 				 void *external_spt);
 
 	/* Update external page table from spte getting removed, and flush TLB. */
-	int (*remove_external_spte)(struct kvm *kvm, gfn_t gfn, enum pg_level level,
-				    kvm_pfn_t pfn_for_gfn);
+	void (*remove_external_spte)(struct kvm *kvm, gfn_t gfn, enum pg_level level,
+				     u64 spte);
 
 	bool (*has_wbinvd_exit)(void);
 
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 3ea2dd64ce72..78ee085f7cbc 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -362,9 +362,6 @@ static void tdp_mmu_unlink_sp(struct kvm *kvm, struct kvm_mmu_page *sp)
 static void remove_external_spte(struct kvm *kvm, gfn_t gfn, u64 old_spte,
 				 int level)
 {
-	kvm_pfn_t old_pfn = spte_to_pfn(old_spte);
-	int ret;
-
 	/*
 	 * External (TDX) SPTEs are limited to PG_LEVEL_4K, and external
 	 * PTs are removed in a special order, involving free_external_spt().
@@ -377,9 +374,8 @@ static void remove_external_spte(struct kvm *kvm, gfn_t gfn, u64 old_spte,
 
 	/* Zapping leaf spte is allowed only when write lock is held. */
 	lockdep_assert_held_write(&kvm->mmu_lock);
-	/* Because write lock is held, operation should success. */
-	ret = kvm_x86_call(remove_external_spte)(kvm, gfn, level, old_pfn);
-	KVM_BUG_ON(ret, kvm);
+
+	kvm_x86_call(remove_external_spte)(kvm, gfn, level, old_spte);
 }
 
 /**
diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index 8cb6a2627eb2..07f9ad1fbfb6 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -1809,12 +1809,12 @@ static int tdx_sept_free_private_spt(struct kvm *kvm, gfn_t gfn,
 	return tdx_reclaim_page(virt_to_page(private_spt));
 }
 
-static int tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn,
-					enum pg_level level, kvm_pfn_t pfn)
+static void tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn,
+					 enum pg_level level, u64 spte)
 {
+	struct page *page = pfn_to_page(spte_to_pfn(spte));
 	int tdx_level = pg_level_to_tdx_sept_level(level);
 	struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm);
-	struct page *page = pfn_to_page(pfn);
 	gpa_t gpa = gfn_to_gpa(gfn);
 	u64 err, entry, level_state;
 	int ret;
@@ -1825,15 +1825,15 @@ static int tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn,
 	 * there can't be anything populated in the private EPT.
 	 */
 	if (KVM_BUG_ON(!is_hkid_assigned(to_kvm_tdx(kvm)), kvm))
-		return -EIO;
+		return;
 
 	/* TODO: handle large pages. */
 	if (KVM_BUG_ON(level != PG_LEVEL_4K, kvm))
-		return -EIO;
+		return;
 
 	ret = tdx_sept_zap_private_spte(kvm, gfn, level, page);
 	if (ret <= 0)
-		return ret;
+		return;
 
 	/*
 	 * TDX requires TLB tracking before dropping private page.  Do
@@ -1862,17 +1862,16 @@ static int tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn,
 
 	if (KVM_BUG_ON(err, kvm)) {
 		pr_tdx_error_2(TDH_MEM_PAGE_REMOVE, err, entry, level_state);
-		return -EIO;
+		return;
 	}
 
 	err = tdh_phymem_page_wbinvd_hkid((u16)kvm_tdx->hkid, page);
 	if (KVM_BUG_ON(err, kvm)) {
 		pr_tdx_error(TDH_PHYMEM_PAGE_WBINVD, err);
-		return -EIO;
+		return;
 	}
 
 	tdx_clear_page(page);
-	return 0;
 }
 
 void tdx_deliver_interrupt(struct kvm_lapic *apic, int delivery_mode,
-- 
2.51.0.318.gd7df087d1a-goog