From nobody Mon Feb 9 13:01:16 2026 Received: from mail-pg1-f202.google.com (mail-pg1-f202.google.com [209.85.215.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C461B36CE0D for ; Thu, 29 Jan 2026 01:16:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769649398; cv=none; b=p3O8imwGbPg6NkBhcQt7m7fHE+3VCUHoAwgHfoEQvUzKLimc+o/cBBM2QKRHNVADPBtr2JqkybyGNPHdsyFsTWdWWIf/o+gCXauXeuPHmHjCgE8nvIBuRBCVmOWxYYz5yWzifcAXYRUFyzeH9Dyzz6DvchjQ3RR/s9HQTHeYQa4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769649398; c=relaxed/simple; bh=ZA7lO6Iqcxv2nIH6jvLo0wih4TGT7nAoCV3mCXKZU8Q=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=ebuD3JM/MxWV0Gg3YP0L80pLKo2puuLKl+zcOfijFqPx1oJ0ZaFlBE+mEc40PzEGJwCSg59xkdmDUCIEvs/5h5An2CHhpRVDBeoUNFc23dlD6BaYU8sjZi0nnS6Ka7u9BIPaGrL2oHnqVoAADUhVPfXaIMW6gfH+SGu4zx+B2/o= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=nhqDFrpt; arc=none smtp.client-ip=209.85.215.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="nhqDFrpt" Received: by mail-pg1-f202.google.com with SMTP id 41be03b00d2f7-c6133262e4eso233408a12.2 for ; Wed, 28 Jan 2026 17:16:36 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1769649396; x=1770254196; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=yjclvkjmE1zw/GHq/jW5Y/EQUpO3A2fBpqR5d3bbX+8=; b=nhqDFrptFZSlTjl5ZcbC29HI4IjTrLVEH06tZSxjzl9PrBFvmlrkxxiF8cbIl1Im1X eTh72iMiNYC/MAcrzvZ0sCehqpIj94BMP4k/fZIFTr34s+Co8LArZO6xMjr8rNLyEnnH upoyXiPxcvxyHFRi0wUL4ZovSaf2gSOq4ei4mQUvoJkqqlWR1V37Hv8QIMacC9T3VV5b pRSlssFfjakI+Sn6hWWA7EFKuMH4Dq0TbmfSX0uGz3rsuWjH3JyXAFzlZvcaAim1tpLc TsNBN9u0IJue1UJtuJHgDgWf06h9o0BaegCbrPQKAdkii2qkufZyIvoav7vpqFnUBHk2 L17A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1769649396; x=1770254196; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=yjclvkjmE1zw/GHq/jW5Y/EQUpO3A2fBpqR5d3bbX+8=; b=a1ldzw07cHSihsVyh7UA4tAZ9QeqSkcrnVlQvKfPs9g8ivgEE/9dPvPVHohk/ooAF9 rHyH6lz4x1o3jplPrRCiU9EUzp2eL0Ewle1OIkcgubOpCcYwJAgzvU1OMfyrBVBgdDCw Hq08BDu7aH6CVQntaUq8FelA3HjiKlxMH7/BHGc5lTBCcsmdqClgZ69rePNR8VO//sC/ TDlRXuK6vxK2Jic+sfv/FQQXVCmbiC7nvWVCuODDymMP7wGOdEtVHIAX5MHlgsy/5do4 D13TdMkv2OxpiDRexku3j5ZstWtUcl/UfV//9Z53O84Y6R0Y45Jz87V2icUKjn/nN30i h20w== X-Gm-Message-State: AOJu0YwNgVGlwjoSuo3VgreAYq8NZha7jBH6C9QHqSxpmxBxdtljETt7 VI1hPTCgj6fPYFwHYyzXOB5WCSWXh7v3b/Y7A0ggJzOvqoAty1bfKQA6RpniXGf8V4zA3jXR6xL kU7IxdA== X-Received: from pjof4.prod.google.com ([2002:a17:90a:8e84:b0:34c:cb46:dad7]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a20:7484:b0:366:14af:9bbb with SMTP id adf61e73a8af0-38ec65898bfmr7510420637.69.1769649396157; Wed, 28 Jan 2026 17:16:36 -0800 (PST) Reply-To: Sean Christopherson Date: Wed, 28 Jan 2026 17:15:08 -0800 In-Reply-To: <20260129011517.3545883-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260129011517.3545883-1-seanjc@google.com> X-Mailer: git-send-email 2.53.0.rc1.217.geba53bf80e-goog Message-ID: <20260129011517.3545883-37-seanjc@google.com> Subject: [RFC PATCH v5 36/45] KVM: TDX: Move S-EPT page demotion TODO to tdx_sept_set_private_spte() From: Sean Christopherson To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, Kiryl Shutsemau , Sean Christopherson , Paolo Bonzini Cc: linux-kernel@vger.kernel.org, linux-coco@lists.linux.dev, kvm@vger.kernel.org, Kai Huang , Rick Edgecombe , Yan Zhao , Vishal Annapurve , Ackerley Tng , Sagi Shahar , Binbin Wu , Xiaoyao Li , Isaku Yamahata Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Now that handle_changed_spte() can handles all mirror SPTE updates, move the TDP MMU's assertion that it doesn't replace a shadow-present mirror SPTE with another shadow-present SPTE into TDX, in the form of a TODO that calls out that KVM needs to add support for splitting/demoting hugepage. Drop the "!is_leaf" condition so that an unexpected/unsupported update to a shadow-present S-EPT triggers a KVM_BUG_ON(), versus being silently ignored (well, silent until it causes explosions in the future). Signed-off-by: Sean Christopherson --- arch/x86/kvm/mmu/tdp_mmu.c | 9 +-------- arch/x86/kvm/vmx/tdx.c | 5 ++++- 2 files changed, 5 insertions(+), 9 deletions(-) diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index d49aecba18d8..3b0da898824a 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -572,7 +572,7 @@ static void handle_changed_spte(struct kvm *kvm, int as= _id, tdp_ptep_t sptep, 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 (was_leaf && is_mirror_sptep(sptep) && !is_leaf) + else if (was_leaf && is_mirror_sptep(sptep)) KVM_BUG_ON(kvm_x86_call(set_external_spte)(kvm, gfn, old_spte, new_spte, level), kvm); } @@ -704,13 +704,6 @@ static u64 tdp_mmu_set_spte(struct kvm *kvm, int as_id= , tdp_ptep_t sptep, =20 handle_changed_spte(kvm, as_id, sptep, gfn, old_spte, new_spte, level, fa= lse); =20 - /* - * Users that do non-atomic setting of PTEs don't operate on mirror - * roots. Bug the VM as this path doesn't propagate such writes to the - * external page tables. - */ - KVM_BUG_ON(is_mirror_sptep(sptep) && is_shadow_present_pte(new_spte), kvm= ); - return old_spte; } =20 diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index e6ac4aca8114..59b7ba36d3d9 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -1850,7 +1850,10 @@ static int tdx_sept_remove_private_spte(struct kvm *= kvm, gfn_t gfn, static int tdx_sept_set_private_spte(struct kvm *kvm, gfn_t gfn, u64 old_s= pte, u64 new_spte, enum pg_level level) { - if (is_shadow_present_pte(old_spte)) + /* TODO: Support replacing huge SPTE with non-leaf SPTE. (a.k.a. demotion= ). */ + if (KVM_BUG_ON(is_shadow_present_pte(old_spte) && is_shadow_present_pte(n= ew_spte), kvm)) + return -EIO; + else if (is_shadow_present_pte(old_spte)) return tdx_sept_remove_private_spte(kvm, gfn, old_spte, level); =20 if (KVM_BUG_ON(!is_shadow_present_pte(new_spte), kvm)) --=20 2.53.0.rc1.217.geba53bf80e-goog