From nobody Mon Apr 6 10:43:19 2026 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 21B8E3A8747 for ; Mon, 30 Mar 2026 07:58:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774857520; cv=none; b=AscHmHaKF+OcmzExN34ElkazfI3Lk1e2t9yP9LzEa7KFl2HobgqkREICot1TOM2/CzhsooRbsqP6TuTmMaiAhrPqJfrDs2gbD0cSlmVso6Yex1JrmMQMXaRUsMdkEVSA3n1QRbeWva0X6t8Q1qv39qlMa6giD9UQHt5ByP8q2CI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774857520; c=relaxed/simple; bh=zEZGwGF3sKc0G9zq1ffG0PV9TQ4YaNhIAp7e0h+68pU=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=Ejif+T045ZmcS1xgbUWlGE4c0sR9CFKFAv1F5Vs8bcm8coZg4SW1ea6w+M1U45D0ItuHX54jthwNAgXCYUtgQd9w6Rfv2hSfiUDHoPp+/mcaOqz0AN1siuQwmjO7XBQFiCYAWleFOMipxIaX457lLS13ifpydV0igyJC3wy61Ic= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=KUXXfz5M; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b=snK2Ns/c; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="KUXXfz5M"; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b="snK2Ns/c" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1774857518; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=I9UHxN7TKiM+B8XGIaW8UV2fs43HChjHFnISdi8ej/0=; b=KUXXfz5MjhsQTQwbOTY35MEN17/zCDxj0tpasDhApEKJBXK1FPjSV6jw9uiaKDooHwaKpA 5fFY9rpV7vIarDkueWw4lNph1yd0UjlIC1zDac+O4RtXB8G5e/zMpTensMyNt8Nm754WeE Khd4iyQtm9hMi7nMUOvD2dd+30aV4dk= Received: from mail-wr1-f69.google.com (mail-wr1-f69.google.com [209.85.221.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-384-aEqcgprbMrGGUYYXCZrIag-1; Mon, 30 Mar 2026 03:58:36 -0400 X-MC-Unique: aEqcgprbMrGGUYYXCZrIag-1 X-Mimecast-MFC-AGG-ID: aEqcgprbMrGGUYYXCZrIag_1774857515 Received: by mail-wr1-f69.google.com with SMTP id ffacd0b85a97d-43ba02dc34bso2307766f8f.1 for ; Mon, 30 Mar 2026 00:58:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=google; t=1774857514; x=1775462314; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=I9UHxN7TKiM+B8XGIaW8UV2fs43HChjHFnISdi8ej/0=; b=snK2Ns/cMIQbzd3fAvTfGWy2J1uhkaxgwxvE+sZxNsCSwKrWvaKoos3+SSnueadsGE n8xh9SUUw7cSNOVbP1Pc7hFzGI0u/4NukHXkE/IutV+nn27UOI7rhgJP97Hxc2MsAg5N jovKvIfxX207ao8z7IllRfAq46ddajgwBAHJqd5If9Tx1czy9cQoikx37s40Dht+oQr5 mxbcXfJy/9V4a/YgWHjCZJi3fjnAI0m9n0lMGGpTXfh9SMEkA6gjlqnEdIOmerqT/elN 4FUttZ5wMvYxkjh5B08CU5s74FvbLuXjWPmNHH57O5aekRCocI8QkTNlThf0o/50FgiP kUeg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1774857514; x=1775462314; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=I9UHxN7TKiM+B8XGIaW8UV2fs43HChjHFnISdi8ej/0=; b=SPj51RnPpFwplMyKdF8RSB5QlsXlEKoVsaNIKmuFaAvAWiWEjeaH1i4WPfVCBE+8r4 4OsAPvw/7XnRCwV1N18BebWF0Bu+ZrfF5XYo8aS0kvVLZ+9xRqhlbSeM+o75QIaQvDqM UatvTTfvWNc9NyWhTf7Ed+CspXk/uFvjvpjYgzArchttNp8qDnELiCxRwvV23SnIpvWB XR6P1uY6edf3A/6Zhn2oFRQqt5aAuitoNQ42N1jFuoJA5JhbHp9alhqSzMDIZXbC6xDc 2ih/Fj45Mn09TMzOhELrrmQwNWUqpRFp5U3+8+U21WajXMH4MzPEjGdMOXIk0sYdBVhD 6Vnw== X-Gm-Message-State: AOJu0Yw448TKou1bFi9afRxPinkNY1Bc3nuezgXxYMM4SPuBZr1e7Geg 9zd8FDFkf9GyHeB9XM7mInuHFY9K9AKz5HZPuglgfAr3k7kxvG2MXn4E2oa6P5zU6jxvAYgNqax xM11cIvsY/cDes3bM+R76ttavsg6DBCM7MgMMzV2CDhaLuawu0//vKl/nyggA3Nlb7i2veWgWkV QDD/xEo6063d1ehxo+xFJHpjLSNo5tYgXwVW04VqmbZAg30m823Q== X-Gm-Gg: ATEYQzwtQVJT+YUGmHDIRWVRVnJ2fpp7taGSWsyq8VOo1v6MBPkep3TtwEQltyg7QZ+ wybDxxz2xaMkOtvFqkmOgJWRZW9UeVR6aAQ3ZSKHXh89fxu8JdK/EQ1Rs48/yvJXeypUnhtaWyu 87HcUV57C4m6pcD3ZQRk0wpnYk3HZ6fZ72azovM6/FLg1Ezsw4ShHyx/5smeRNXg+vV4xyWKESn D8gE7Ag2XzcuxJdO9vLU7AsqCpRIZ4Dcy0RpFlRrUtBeZIKzK8xkPiD4RAChgQBgPyFd0p/WSFs ZASnz6YaHuTF6huhImPqrs6MGIaHaR61ZHERBHFITkdYSdJk1aViKTmeH2g7uBynuEMBiipb9qN WW/X/3xIRBbtH6x2sPSCrgttVVjz7jUVkHrUGzST4z4bHlB3qDNFnuTMASEPgdXkgyE9uqasplI XycYONqe3CrNTA+mcQMcR3ospe X-Received: by 2002:a05:6000:2307:b0:43b:3d02:7806 with SMTP id ffacd0b85a97d-43b9ea4a457mr18934817f8f.28.1774857514370; Mon, 30 Mar 2026 00:58:34 -0700 (PDT) X-Received: by 2002:a05:6000:2307:b0:43b:3d02:7806 with SMTP id ffacd0b85a97d-43b9ea4a457mr18934767f8f.28.1774857513811; Mon, 30 Mar 2026 00:58:33 -0700 (PDT) Received: from [192.168.10.48] ([151.49.85.67]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43cf24739easm17845984f8f.30.2026.03.30.00.58.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 30 Mar 2026 00:58:33 -0700 (PDT) From: Paolo Bonzini To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Sean Christopherson , Alexander Bulekov , Fred Griffoul , stable@vger.kernel.org Subject: [PATCH for-6.1] KVM: x86/mmu: Drop/zap existing present SPTE even when creating an MMIO SPTE Date: Mon, 30 Mar 2026 09:58:31 +0200 Message-ID: <20260330075831.153407-1-pbonzini@redhat.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Sean Christopherson commit aad885e774966e97b675dfe928da164214a71605 upstream. When installing an emulated MMIO SPTE, do so *after* dropping/zapping the existing SPTE (if it's shadow-present). While commit a54aa15c6bda3 was right about it being impossible to convert a shadow-present SPTE to an MMIO SPTE due to a _guest_ write, it failed to account for writes to guest memory that are outside the scope of KVM. E.g. if host userspace modifies a shadowed gPTE to switch from a memslot to emulted MMIO and then the guest hits a relevant page fault, KVM will install the MMIO SPTE without first zapping the shadow-present SPTE. ------------[ cut here ]------------ is_shadow_present_pte(*sptep) WARNING: arch/x86/kvm/mmu/mmu.c:484 at mark_mmio_spte+0xb2/0xc0 [kvm], CP= U#0: vmx_ept_stale_r/4292 Modules linked in: kvm_intel kvm irqbypass CPU: 0 UID: 1000 PID: 4292 Comm: vmx_ept_stale_r Not tainted 7.0.0-rc2-ea= febd2d2ab0-sink-vm #319 PREEMPT Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:mark_mmio_spte+0xb2/0xc0 [kvm] Call Trace: mmu_set_spte+0x237/0x440 [kvm] ept_page_fault+0x535/0x7f0 [kvm] kvm_mmu_do_page_fault+0xee/0x1f0 [kvm] kvm_mmu_page_fault+0x8d/0x620 [kvm] vmx_handle_exit+0x18c/0x5a0 [kvm_intel] kvm_arch_vcpu_ioctl_run+0xc55/0x1c20 [kvm] kvm_vcpu_ioctl+0x2d5/0x980 [kvm] __x64_sys_ioctl+0x8a/0xd0 do_syscall_64+0xb5/0x730 entry_SYSCALL_64_after_hwframe+0x4b/0x53 RIP: 0033:0x47fa3f ---[ end trace 0000000000000000 ]--- Reported-by: Alexander Bulekov Debugged-by: Alexander Bulekov Suggested-by: Fred Griffoul Fixes: a54aa15c6bda3 ("KVM: x86/mmu: Handle MMIO SPTEs directly in mmu_set_= spte()") Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson Signed-off-by: Paolo Bonzini --- arch/x86/kvm/mmu/mmu.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 04d060f37053..a9f24eeb4477 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -2814,12 +2814,6 @@ static int mmu_set_spte(struct kvm_vcpu *vcpu, struc= t kvm_memory_slot *slot, pgprintk("%s: spte %llx write_fault %d gfn %llx\n", __func__, *sptep, write_fault, gfn); =20 - if (unlikely(is_noslot_pfn(pfn))) { - vcpu->stat.pf_mmio_spte_created++; - mark_mmio_spte(vcpu, sptep, gfn, pte_access); - return RET_PF_EMULATE; - } - if (is_shadow_present_pte(*sptep)) { /* * If we overwrite a PTE page pointer with a 2MB PMD, unlink @@ -2841,6 +2835,15 @@ static int mmu_set_spte(struct kvm_vcpu *vcpu, struc= t kvm_memory_slot *slot, was_rmapped =3D 1; } =20 + if (unlikely(is_noslot_pfn(pfn))) { + vcpu->stat.pf_mmio_spte_created++; + mark_mmio_spte(vcpu, sptep, gfn, pte_access); + if (flush) + kvm_flush_remote_tlbs_with_address(vcpu->kvm, gfn, + KVM_PAGES_PER_HPAGE(level)); + return RET_PF_EMULATE; + } + wrprot =3D make_spte(vcpu, sp, slot, pte_access, gfn, pfn, *sptep, prefet= ch, true, host_writable, &spte); =20 --=20 2.53.0