From nobody Mon Apr 6 10:32:54 2026 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 944FD382367 for ; Mon, 30 Mar 2026 08:01:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774857712; cv=none; b=q5t3upFWfO7IPD2RMRuhqHZZpl6G/wC0A5RDVfb5/VfFDqyEqjpqTslPVsZzSAgcXC8LjZ3J0EPZb7OIhvk7HJrF2AaFCXTis2fWB4MiAo1uhmQj+qwJpG0+RKvu1Aj9pitzK9bgHayG7rBLdiUN6nva5/959wzZmXO/F//Sbag= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774857712; c=relaxed/simple; bh=woHof7wfkrzWjNOrAi7nzaTttmXDmDaMclAa0u+1qkM=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=jbqF7PTTsbxodHj1WeuzFWmVoQ17O/NpXRfAAUT6ACqpkqFCSsAl8Zf6xYdDuHt7k2YsIZzX+TwwxPb3AAvMfcKT+I7zgr23VC+MCjT18iULAEpUAfzzNMJ1254/KulkWbdWErmaT1AVhgQ+BArnbBrYiZWZsznRCzJSGt5rL9Y= 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=G2FbehJZ; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b=cKL8TGw9; arc=none smtp.client-ip=170.10.129.124 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="G2FbehJZ"; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b="cKL8TGw9" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1774857710; 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=ZMEDTog/V2EbiuJTJRgUNGd1J4MxLV+lIo/zs81mrgs=; b=G2FbehJZjs2EqJNJ191uU4m1jZPX8E/JJGn6uutdga4yWMw0kZvjzxd5ZKXFOCjY7TaBGg 4cA+Xdc/wjVHuYBzEwvjQNcjrtbQQZ6FGgPdZpaWrjnFCkDIcUB6LDa9WuOIk62WFi+PQl PcqyovUShOpy+22mQ909MX+ooyaIqks= Received: from mail-wm1-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-695-_BqzWEcTMu69wyXGZsqmig-1; Mon, 30 Mar 2026 04:01:49 -0400 X-MC-Unique: _BqzWEcTMu69wyXGZsqmig-1 X-Mimecast-MFC-AGG-ID: _BqzWEcTMu69wyXGZsqmig_1774857708 Received: by mail-wm1-f72.google.com with SMTP id 5b1f17b1804b1-4852d27f473so24201845e9.1 for ; Mon, 30 Mar 2026 01:01:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=google; t=1774857707; x=1775462507; 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=ZMEDTog/V2EbiuJTJRgUNGd1J4MxLV+lIo/zs81mrgs=; b=cKL8TGw9JS13WZEJGUXPN2Sxu4TfZMBm+1JOZIjSMPvRd/2uYVirj3QeDh79TkD4tz sKfyH2b8lt6/4bBV54aTmXeNp0XIPEhx/fKl9yFK3+cTRiD63FV2Lxg1y02cmfVeNnxC IGqJ1g0jEXVrBYgm20sf5VDOp0TPih6u3LFOl/EX6rZoCipKLQ3h4oaIcXgCpBl8ktob kz4sPq2AoSfcYdaEjVeIU9mHqe1sEC55hq/qytxZ5yj1Zj3JDg19MZiFbgL0uI7+p7S+ HGMwgvhFixbZDlqxZOGmq4ZPWh20BkxaNMojGlDFTVL2S7IsCLbbCF8wRyZfSg8SqSMv P0DA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1774857707; x=1775462507; 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=ZMEDTog/V2EbiuJTJRgUNGd1J4MxLV+lIo/zs81mrgs=; b=PTR78Q3Kp02b4H0gRxPyRVhq7C55XI+yCY7GJmFf0iQ/0q/A+nbiEDNETg9bP8+MS1 4TO62dma2MohHcwoKy6vU5kSRE7Mr7oi0sauQ4Wbc5XvEVT/5ZlqJrs2WqKOMt8w8ol0 N84JPIzCfi11IKIlx4xKdvvTbx5yA9UpOtrHluJyOtJuJgxbvg1qDEQH9jZsHf3A9Hwh R0aYCXgb1A0DPhej/FgBDZ1sqjlJu3klw1S2RK+FzsWlfJCRCNWV9aBxD/IhvyNvs5Do szMTZdmKYwYeT/Mfj7lOk79qqlH42xWSk3/Q5GWZj/5I00DC2a37YyXndxyZ9ewEia4k QHuw== X-Gm-Message-State: AOJu0YzMu9GPGOhmJAANO8iGLMeMjtE1nnFN/oLvyarn0jcxxtNEBweN NniQHnFvlYZ8fm/pCt+IKxgJyNdlLkePDtKIT7j8N3eP8eP1YGRdz0QVdIz4O0PwxQS5EbKXcrF 8yL6RheOE6ZQYEkh7EN2gx2+ZK2TEDYU88QlAALyL0ulwoyvKuiNi8vAV43OYk/T5QwXP3VqMd7 4HsjkwSwD1uzHQhW+2gfETRI/P/go1RcqHCuuyIYJzWkCrQrKsIA== X-Gm-Gg: ATEYQzynuulliN7DKsJRX1KoDnXjF5V+s56/gUpu6xK92UlcbU81MBX/zO/NjMI0p0a 3lDLezUvY2OhWUb4eXVFLPAkM0niPf1kMruDZ4G3MQi2xdG2hYle97jsOij77UWqKVhMcfJ+cCp bY777iTg8UmXE2UkI2eeSrytcCwdNkK0IxSQG6br5GYpQENvOp9Ifhylg10gnOS+JfgG7+NanFt /76rkzcsxHe9M2oK3K2g8xSBuZZPK0mX0LM3QK8UI8kTL3ZwremE3FmXEnqsGAvKtubs4nEJVeH kEhOmWU/c1wzIOp+7kDouctXuI085XP83iTid3e5TLN/mRJyEj0PYSWmXYW78rblVUuGlFUHiS4 nX7lLYyYKG8nC5vpzsQU95zncDG6YzrbfJ7JeV7R3aOJYcEURg7cJ0AYdvous1tWrAxWQslE6ri bZOpXpA335juOFmFNTdtOQPnbc X-Received: by 2002:a05:600c:529b:b0:485:3ec6:e634 with SMTP id 5b1f17b1804b1-48727d84100mr178013655e9.15.1774857707014; Mon, 30 Mar 2026 01:01:47 -0700 (PDT) X-Received: by 2002:a05:600c:529b:b0:485:3ec6:e634 with SMTP id 5b1f17b1804b1-48727d84100mr178013245e9.15.1774857706436; Mon, 30 Mar 2026 01:01:46 -0700 (PDT) Received: from [192.168.10.48] ([151.49.85.67]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4873069d469sm150150745e9.14.2026.03.30.01.01.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 30 Mar 2026 01:01:45 -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-5.15] KVM: x86/mmu: Drop/zap existing present SPTE even when creating an MMIO SPTE Date: Mon, 30 Mar 2026 10:01:44 +0200 Message-ID: <20260330080144.158592-1-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 | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index acb9193fc06a..3a705aebb52b 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -2717,11 +2717,6 @@ static int mmu_set_spte(struct kvm_vcpu *vcpu, u64 *= sptep, pgprintk("%s: spte %llx write_fault %d gfn %llx\n", __func__, *sptep, write_fault, gfn); =20 - if (unlikely(is_noslot_pfn(pfn))) { - 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 @@ -2743,6 +2738,14 @@ static int mmu_set_spte(struct kvm_vcpu *vcpu, u64 *= sptep, was_rmapped =3D 1; } =20 + if (unlikely(is_noslot_pfn(pfn))) { + 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; + } + set_spte_ret =3D set_spte(vcpu, sptep, pte_access, level, gfn, pfn, speculative, true, host_writable); if (set_spte_ret & SET_SPTE_WRITE_PROTECTED_PT) { --=20 2.53.0