From nobody Mon Feb 9 01:29:16 2026 Received: from mail-pl1-f201.google.com (mail-pl1-f201.google.com [209.85.214.201]) (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 C683A338585 for ; Thu, 29 Jan 2026 01:16:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769649403; cv=none; b=bu9+QY/+u349Gem8kkkb22KtUDuLZ+GUdvZJoSz2eW3PPnUADHWoK3U2ogt59HCwP878vRo7Ukz0Pz7wHVabfBqZ9830nwDFnwXDKY8NGSgsnhDlMN0weu3B4HLxeDcfWrr0fUba2O6wqMgk7WQgYmfLlCmOIGgJde/MFFQidaU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769649403; c=relaxed/simple; bh=748IjIIuUafEiIM83Ku56LzDm+kATSx23KWSqCyn9i4=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=kgCUFLXQ0ckCqXHEd8uob87aOUehv1+x5N8C7UZpdniAhzE9q3Uq6BU+WAHRUsvcZcZAcyVMXbvwjd+8X2h63moShPwyIoyVtnqtWWOOeUKiMVRceX8vbMjkxbTtUQzPgV7t/LkAL70TNp53RzsVC/jYriWadBGTqO7V17T467E= 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=sEuSOiDV; arc=none smtp.client-ip=209.85.214.201 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="sEuSOiDV" Received: by mail-pl1-f201.google.com with SMTP id d9443c01a7336-29f1f79d6afso3992605ad.0 for ; Wed, 28 Jan 2026 17:16:41 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1769649401; x=1770254201; 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=QSAxn7KWvy+xJKU0DNDq3fpgZfT3mJRUWulB6u+627E=; b=sEuSOiDVz3kgLmg+QRTGoCJnBp6tAVQhpvov++AvSZYsTWc3bJowjohb2kmc2rCWLD KBV2VbnwNVtw31lHjPU18xL3yiWcrnAe43avbY8es96+TWu1hOY4g3PaTl488/ZDuxlu m1eAh1taMnwxvgjkS9HT27noMNxXULl46D6+XfcYsy2GzaUwapx2YnQykkr1DkLmcrNW S2f6HGIAQgp3DkdBYURltgW6pHAiFwg2Utwa2ubD+9p2JwO6pJkyn8zk4HPS8RtNQE3o uVHdg02GBC8MayI6PJKfGHIdPRli8dqfVHONTS2Vth4oI0TTShHLzUL/3rnQFMFjKSj1 1Mrw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1769649401; x=1770254201; 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=QSAxn7KWvy+xJKU0DNDq3fpgZfT3mJRUWulB6u+627E=; b=Ck3wu/nIdonJdnjpndcu0Kye5aeRKVX7sVqmsIqHPBhloUxkLFL3IRqNpqOdWbb5cc Pmhsxyi+/qv92vXVE/+N8phJv/+6mKGheGceumWTcNwY4Y3yyJ/ZW7JTvmlVS9s0v6Ou vu+x1WupXOixncz39vkX2KETOz6wzkTIZ9XSo6/ptSrf2uE+xPCLcb88vniF/IDmZV6u TmmLCg+bz0tE+fcNkcH2MDe3rGHW9HsJy0L1+5ghb2Sqtawc1/ODYGHpnei8IKFCUxsF aNkF1LTdTv0AHEcDqX4wm4P3K1AaTeXAe6RcnWbx58Q4YN9vWMs2X8wDyd/8AGmqBxJV b84g== X-Gm-Message-State: AOJu0YzrMCTZEznsyo4uNoyRWkmHFc9A+YT3LgFzER4okeV73MquK4+R biWvXt0h3P/lB1LjSbeXwFbOGbnQeYyBSkgNzK9e6uYdV57QiTFSIKtj9GBz4YH2IrULF2ySWlr f1tEdeQ== X-Received: from pght14.prod.google.com ([2002:a63:eb0e:0:b0:c1d:1cf6:2897]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a20:568e:b0:38d:fc34:c887 with SMTP id adf61e73a8af0-38ec654856dmr6765109637.65.1769649401195; Wed, 28 Jan 2026 17:16:41 -0800 (PST) Reply-To: Sean Christopherson Date: Wed, 28 Jan 2026 17:15:11 -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: <20260129011517.3545883-40-seanjc@google.com> Subject: [RFC PATCH v5 39/45] KVM: TDX: Add core support for splitting/demoting 2MiB S-EPT to 4KiB 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" From: Yan Zhao Add support for splitting, a.k.a. demoting, a 2MiB S-EPT hugepage to its 512 constituent 4KiB pages. As per the TDX-Module rules, first invoke MEM.RANGE.BLOCK to put the huge S-EPTE entry into a splittable state, then do MEM.TRACK and kick all vCPUs outside of guest mode to flush TLBs, and finally do MEM.PAGE.DEMOTE to demote/split the huge S-EPT entry. Assert the mmu_lock is held for write, as the BLOCK =3D> TRACK =3D> DEMOTE sequence needs to be "atomic" to guarantee success (and because mmu_lock must be held for write to use tdh_do_no_vcpus()). Note, even with kvm->mmu_lock held for write, tdh_mem_page_demote() may contend with tdh_vp_enter() and potentially with the guest's S-EPT entry operations. Therefore, wrap the call with tdh_do_no_vcpus() to kick other vCPUs out of the guest and prevent tdh_vp_enter() to ensure success. Signed-off-by: Xiaoyao Li Signed-off-by: Isaku Yamahata Signed-off-by: Yan Zhao [sean: wire up via tdx_sept_link_private_spt(), massage changelog] Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/tdx.c | 51 +++++++++++++++++++++++++++++++++++++++--- 1 file changed, 48 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index e90610540a0b..af63364c8713 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -1776,6 +1776,52 @@ static struct page *tdx_spte_to_external_spt(struct = kvm *kvm, gfn_t gfn, return virt_to_page(sp->external_spt); } =20 +/* + * Split a huge mapping into the target level. Currently only supports 2M= iB + * mappings (KVM doesn't yet support 1GiB mappings for TDX guests). + * + * Invoke "BLOCK + TRACK + kick off vCPUs (inside tdx_track())" since DEMO= TE + * now does not support yet the NON-BLOCKING-RESIZE feature. No UNBLOCK is + * needed after a successful DEMOTE. + * + * Under write mmu_lock, kick off all vCPUs (inside tdh_do_no_vcpus()) to = ensure + * DEMOTE will succeed on the second invocation if the first invocation re= turns + * BUSY. + */ +static int tdx_sept_split_private_spte(struct kvm *kvm, gfn_t gfn, u64 old= _spte, + u64 new_spte, enum pg_level level) +{ + struct kvm_vcpu *vcpu =3D kvm_get_running_vcpu(); + struct kvm_tdx *kvm_tdx =3D to_kvm_tdx(kvm); + gpa_t gpa =3D gfn_to_gpa(gfn); + u64 err, entry, level_state; + struct page *external_spt; + + lockdep_assert_held_write(&kvm->mmu_lock); + + external_spt =3D tdx_spte_to_external_spt(kvm, gfn, new_spte, level); + if (!external_spt) + return -EIO; + + if (KVM_BUG_ON(!vcpu || vcpu->kvm !=3D kvm, kvm)) + return -EIO; + + err =3D 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 -EIO; + + tdx_track(kvm); + + err =3D tdh_do_no_vcpus(tdh_mem_page_demote, kvm, &kvm_tdx->td, gpa, + level, spte_to_pfn(old_spte), external_spt, + &to_tdx(vcpu)->pamt_cache, &entry, &level_state); + if (TDX_BUG_ON_2(err, TDH_MEM_PAGE_DEMOTE, entry, level_state, kvm)) + return -EIO; + + return 0; +} + static int tdx_sept_link_private_spt(struct kvm *kvm, gfn_t gfn, u64 new_s= pte, enum pg_level level) { @@ -1853,9 +1899,8 @@ static int tdx_sept_remove_private_spte(struct kvm *k= vm, 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) { - /* 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; + if (is_shadow_present_pte(old_spte) && is_shadow_present_pte(new_spte)) + return tdx_sept_split_private_spte(kvm, gfn, old_spte, new_spte, level); else if (is_shadow_present_pte(old_spte)) return tdx_sept_remove_private_spte(kvm, gfn, old_spte, level); =20 --=20 2.53.0.rc1.217.geba53bf80e-goog