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authorSean Christopherson <seanjc@google.com>2026-05-09 15:57:09 +0800
committerSean Christopherson <seanjc@google.com>2026-05-27 17:19:20 -0700
commit6eae9ce9461cc0ba16a779b49a70eaab2271a969 (patch)
tree6fbec5d9e6aaa898dca871b24a669f3095cdbb3a /arch
parentc74893aa56f4e7515c0877c5230f9f42357ff044 (diff)
downloadlinux-next-history-6eae9ce9461cc0ba16a779b49a70eaab2271a969.tar.gz
KVM: TDX: Drop kvm_x86_ops.remove_external_spte()
Drop kvm_x86_ops.remove_external_spte(), and instead handle the removal of leaf SPTEs in the S-EPT (a.k.a. external page table) in kvm_x86_ops.set_external_spte(). This will also allow extending tdx_sept_set_private_spte() to support splitting a huge S-EPT entry without needing yet another kvm_x86_ops hook. Now all changes for removing leaf mirror SPTEs are propagated through kvm_x86_ops.set_external_spte(). - When removing leaf mirror SPTEs under shared mmu_lock (though currently no path can trigger this scenario and TDX does not support this scenario), tdx_sept_remove_private_spte() may produce a warning due to lockdep_assert_held_write() or may return -EIO and trigger TDX_BUG_ON() due to concurrent BLOCK, TRACK, REMOVE. - When removing leaf mirror SPTEs under exclusive mmu_lock, all errors are unexpected. If any error occurs in this scenario, tdx_sept_remove_private_spte() will return -EIO and trigger KVM_BUG_ON(). A redundant KVM_BUG_ON() call will also be triggered in TDP MMU core in handle_changed_spte(), which is benign (the WARN will fire if and only if the VM isn't already bugged). Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com> Signed-off-by: Yan Zhao <yan.y.zhao@intel.com> Link: https://patch.msgid.link/20260509075709.4322-1-yan.y.zhao@intel.com Signed-off-by: Sean Christopherson <seanjc@google.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/include/asm/kvm-x86-ops.h1
-rw-r--r--arch/x86/include/asm/kvm_host.h3
-rw-r--r--arch/x86/kvm/mmu/tdp_mmu.c37
-rw-r--r--arch/x86/kvm/vmx/tdx.c39
4 files changed, 31 insertions, 49 deletions
diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
index 2cb393000ee92..771d991562caf 100644
--- a/arch/x86/include/asm/kvm-x86-ops.h
+++ b/arch/x86/include/asm/kvm-x86-ops.h
@@ -98,7 +98,6 @@ KVM_X86_OP_OPTIONAL_RET0(tdp_has_smep)
KVM_X86_OP(load_mmu_pgd)
KVM_X86_OP_OPTIONAL_RET0(set_external_spte)
KVM_X86_OP_OPTIONAL_RET0(free_external_spt)
-KVM_X86_OP_OPTIONAL(remove_external_spte)
KVM_X86_OP(has_wbinvd_exit)
KVM_X86_OP(get_l2_tsc_offset)
KVM_X86_OP(get_l2_tsc_multiplier)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index b8ca43241b115..dc5625950e5bf 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1919,9 +1919,6 @@ struct kvm_x86_ops {
int (*free_external_spt)(struct kvm *kvm, gfn_t gfn, enum pg_level level,
void *external_spt);
- /* Update external page table from spte getting removed, and flush TLB. */
- void (*remove_external_spte)(struct kvm *kvm, gfn_t gfn, enum pg_level level,
- u64 mirror_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 3ba7556a8d2fd..72d323f2d0dcc 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -359,25 +359,6 @@ static void tdp_mmu_unlink_sp(struct kvm *kvm, struct kvm_mmu_page *sp)
spin_unlock(&kvm->arch.tdp_mmu_pages_lock);
}
-static void remove_external_spte(struct kvm *kvm, gfn_t gfn, u64 old_spte,
- int level)
-{
- /*
- * External (TDX) SPTEs are limited to PG_LEVEL_4K, and external
- * PTs are removed in a special order, involving free_external_spt().
- * But remove_external_spte() will be called on non-leaf PTEs via
- * __tdp_mmu_zap_root(), so avoid the error the former would return
- * in this case.
- */
- if (!is_last_spte(old_spte, level))
- return;
-
- /* Zapping leaf spte is allowed only when write lock is held. */
- lockdep_assert_held_write(&kvm->mmu_lock);
-
- kvm_x86_call(remove_external_spte)(kvm, gfn, level, old_spte);
-}
-
/**
* handle_removed_pt() - handle a page table removed from the TDP structure
*
@@ -472,9 +453,6 @@ static void handle_removed_pt(struct kvm *kvm, tdp_ptep_t pt, bool shared)
FROZEN_SPTE, level);
}
handle_changed_spte(kvm, sp, gfn, old_spte, FROZEN_SPTE, level, shared);
-
- if (is_mirror_sp(sp))
- remove_external_spte(kvm, gfn, old_spte, level);
}
if (is_mirror_sp(sp) &&
@@ -585,14 +563,14 @@ static int __handle_changed_spte(struct kvm *kvm, struct kvm_mmu_page *sp,
* SPTE being converted to a hugepage (leaf) or being zapped. Shadow
* pages are kernel allocations and should never be migrated.
*
- * For the mirror page table, propagate changes to present or changes of
- * leaf SPTEs to !present under shared mmu_lock to the external SPTE via
+ * For the mirror page table, propagate all changes to the external SPTE
+ * (except zapping/promotion of non-leaf SPTEs) via the
* set_external_spte() op.
*/
if (was_present && !was_leaf &&
(is_leaf || !is_present || WARN_ON_ONCE(pfn_changed))) {
handle_removed_pt(kvm, spte_to_child_pt(old_spte, level), shared);
- } else if (is_mirror_sp(sp) && (is_present || shared)) {
+ } else if (is_mirror_sp(sp)) {
int r;
r = kvm_x86_call(set_external_spte)(kvm, gfn, old_spte, new_spte, level);
@@ -745,15 +723,6 @@ static u64 tdp_mmu_set_spte(struct kvm *kvm, tdp_ptep_t sptep, u64 old_spte,
handle_changed_spte(kvm, sp, gfn, old_spte, new_spte, level, false);
- /*
- * Users that do non-atomic setting of PTEs don't operate on mirror
- * roots, so don't handle it and bug the VM if it's seen.
- */
- if (is_mirror_sptep(sptep)) {
- KVM_BUG_ON(is_shadow_present_pte(new_spte), kvm);
- remove_external_spte(kvm, gfn, old_spte, level);
- }
-
return old_spte;
}
diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index 8991f08ef81cd..54c85b81a09f5 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -1764,11 +1764,11 @@ static void tdx_track(struct kvm *kvm)
kvm_make_all_cpus_request(kvm, KVM_REQ_OUTSIDE_GUEST_MODE);
}
-static void tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn,
- enum pg_level level, u64 mirror_spte)
+static int tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn,
+ enum pg_level level, u64 old_spte)
{
struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm);
- kvm_pfn_t pfn = spte_to_pfn(mirror_spte);
+ kvm_pfn_t pfn = spte_to_pfn(old_spte);
gpa_t gpa = gfn_to_gpa(gfn);
u64 err, entry, level_state;
@@ -1780,16 +1780,16 @@ static void 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;
+ return -EIO;
/* TODO: handle large pages. */
if (KVM_BUG_ON(level != PG_LEVEL_4K, kvm))
- return;
+ return -EIO;
err = tdh_do_no_vcpus(tdh_mem_range_block, kvm, &kvm_tdx->td, gpa,
level, &entry, &level_state);
if (TDX_BUG_ON_2(err, TDH_MEM_RANGE_BLOCK, entry, level_state, kvm))
- return;
+ return -EIO;
/*
* TDX requires TLB tracking before dropping private page. Do
@@ -1805,22 +1805,40 @@ static void tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn,
err = tdh_do_no_vcpus(tdh_mem_page_remove, kvm, &kvm_tdx->td, gpa,
level, &entry, &level_state);
if (TDX_BUG_ON_2(err, TDH_MEM_PAGE_REMOVE, entry, level_state, kvm))
- return;
+ return -EIO;
err = tdh_phymem_page_wbinvd_hkid((u16)kvm_tdx->hkid, pfn);
if (TDX_BUG_ON(err, TDH_PHYMEM_PAGE_WBINVD, kvm))
- return;
+ return -EIO;
tdx_quirk_reset_paddr(PFN_PHYS(pfn), PAGE_SIZE);
+ return 0;
}
+/*
+ * Handle changes for
+ * (1) leaf SPTEs from non-present to present
+ * (2) non-leaf SPTEs from non-present to present
+ * (3) leaf SPTEs from present to non-present
+ *
+ * - (1) and (2) must be under shared mmu_lock. If (1) and (2) are under
+ * exclusive mmu_lock (currently impossible), contention errors may lead to
+ * KVM_BUG_ON() in handle_changed_spte(), e.g., due to tdx_mem_page_aug(),
+ * tdx_mem_page_add(), or tdh_mem_sept_add() contending with tdh_vp_enter()
+ * due to zero-step mitigation or contending with TDCALLs.
+ * - (3) must be under write mmu_lock. If (3) is under shared mmu_lock
+ * (currently impossible), warnings will be generated due to
+ * lockdep_assert_held_write() or TDX_BUG_ON() caused by concurrent BLOCK,
+ * TRACK, REMOVE.
+ * - Promotion/demotion is not yet supported.
+ */
static int tdx_sept_set_private_spte(struct kvm *kvm, gfn_t gfn, u64 old_spte,
u64 new_spte, enum pg_level level)
{
lockdep_assert_held(&kvm->mmu_lock);
- if (KVM_BUG_ON(is_shadow_present_pte(old_spte), kvm))
- return -EIO;
+ if (is_shadow_present_pte(old_spte))
+ return tdx_sept_remove_private_spte(kvm, gfn, level, old_spte);
if (KVM_BUG_ON(!is_shadow_present_pte(new_spte), kvm))
return -EIO;
@@ -3446,7 +3464,6 @@ int __init tdx_hardware_setup(void)
vt_x86_ops.set_external_spte = tdx_sept_set_private_spte;
vt_x86_ops.free_external_spt = tdx_sept_free_private_spt;
- vt_x86_ops.remove_external_spte = tdx_sept_remove_private_spte;
vt_x86_ops.protected_apic_has_interrupt = tdx_protected_apic_has_interrupt;
return 0;
generated by cgit 1.3-korg (git 2.53.0) at 2026-06-01 04:07:33 +0000