From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 07B644657D6 for ; Tue, 31 Mar 2026 23:17:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774999044; cv=none; b=M+3PByBiJvB77ohiYrE/Dn2/mUU18sf1TTrxesDlJ8+ZpRC4u1NGKG7m4pGd8TaaeEtBk+whmz2QORVry9qZXVPZwgNaug4vQvlTsiF/EjkrQ63GcwHmrUrz/vxW1noeAidwxI6QfAUoggWuipWvwEvwelG8+xoScvYfFFNwJDk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774999044; c=relaxed/simple; bh=W1CB8O9hwmeUfTz1ieyEzxVgRKBi/KZxAgWHXxdlLbA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=uqPcBY4zurBM97CVs762PUmvDAh6WW5GZKXsamJk7bAKUkk0SGx0qPV93PJTLKqMUO06tJn2lT2qzdBRbvG7ti2Cz1hH7FulpHqRnKCzGVJfQKn+BUk+chbeMgN6isJgSbs95z4GZAhc/IPyMsQCAdnlIvebf0QDFo6c1p4WRIA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=i+dkxSaO; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="i+dkxSaO" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 503FEC19423; Tue, 31 Mar 2026 23:17:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774999043; bh=W1CB8O9hwmeUfTz1ieyEzxVgRKBi/KZxAgWHXxdlLbA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=i+dkxSaOUSzqZ4QabiPYZcuWRaZr6IjjJVLEUOw5VN+oO7IbJaOrJ+cWBVvDZC3sb yqe3XWhWgx/iZxLpkn7ZnUCaEeLUnOGAorIeMOPzsKCJmWW4AlyEwEvPx4pHDnFvJ0 R+d5Bz8U/nIcyEZIZ47EadPk6XD9EzsEpBK31R1A0OWheeAoxt9HHvie/BB2ot/u7Q ILrWywHYEUYztrCW3aUps6qBy+veTynRzU0kr4/rkCHRHt2LetYt76/Kit5GsTswu9 hUoKiGjbzqyGsJKbX5xKv67+i/vt7w3fjHn/15peUT1uw5Xe1IZ7NUd9Sq9ROvZMlu KSLBKoROu3mvg== From: Sasha Levin To: stable@vger.kernel.org Cc: Sean Christopherson , Alexander Bulekov , Fred Griffoul , Sasha Levin Subject: [PATCH 6.1.y] KVM: x86/mmu: Drop/zap existing present SPTE even when creating an MMIO SPTE Date: Tue, 31 Mar 2026 19:17:21 -0400 Message-ID: <20260331231721.3421247-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026033049-dial-everyone-46da@gregkh> References: <2026033049-dial-everyone-46da@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Sean Christopherson [ Upstream commit aad885e774966e97b675dfe928da164214a71605 ] 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], CPU#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-eafebd2d2ab0-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 [ replaced kvm_flush_remote_tlbs_gfn() with kvm_flush_remote_tlbs_with_address() and preserved pgprintk call ] Signed-off-by: Sasha Levin --- 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 04d060f370535..ed5ba38bec869 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, struct kvm_memory_slot *slot, pgprintk("%s: spte %llx write_fault %d gfn %llx\n", __func__, *sptep, write_fault, gfn); - 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, struct kvm_memory_slot *slot, was_rmapped = 1; } + 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 = make_spte(vcpu, sp, slot, pte_access, gfn, pfn, *sptep, prefetch, true, host_writable, &spte); -- 2.53.0