From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 61AEE474255; Wed, 12 Aug 2026 16:34:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786552498; cv=none; b=tGFz3KbiariNgfgcl2f/yBJkoUGE6to6cu2SvK0Y+CpQ+FvQKgywzuxQDN8z9YPglg0LHMbc4d2kVPgNYfkZGpjFcC2oZzry5E1vWojPNxn8XyC5EY4C06jbWagsi3vfOKSf5QkimhcoTTmolG43ISUDBPVhO8le7uSOy4O4ZE0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786552498; c=relaxed/simple; bh=bXPw2zrr3HNv+m8YFn+LFkOKPx459ndG5pwc8rj+GeY=; h=From:Subject:To:Cc:In-Reply-To:References:Content-Type:Date: Message-Id; b=MuO5LgYfy3g5fO6dX0flv9X6LPsucUSuC7Nu+8+SqV0XxAUp5ylwUu6RaRDBpXojOKGq4EdHhf/hvl7knXnJMdzLLea+kNDLDJYuwsTZ09JjocxB3WOhaU0GV4F+ccDDuKT/ebP3rkMeejH++DvTDavY5Y8g3z8s3U+G15Qp4AI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BN6B0Pby; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="BN6B0Pby" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AEE411F00A3E; Wed, 12 Aug 2026 16:34:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786552495; bh=upbWTzqNqM69HHErB/pnhM+z1EMh2CSTyRgg19hTYik=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=BN6B0PbykivghP3eIWEIQE6qwIyx/jl+16xazgtlBsUMlKwj8L9ZU4ZMrvIL2Truf CXDnHEirGrH9asaoUM/aBOoT5ANgzlY/eSmPfvHnPRFXlYvxQWkp1V7Uxw2cHANkfS ZsmGOfjQwrJakgeloxJF0ClEJ3AUFDXOcI1AVMthjz2CU8hEOEESoI20AyVYfl+0Jq 4dHHsd95UD3eTwpT28qlGHUZpOS+DG0r3dI6f0LunfJ5VDd9YkhzZh512zwfG5Opj9 JBYGqyP7bmaiiaLjOuZ0lMw2FaKRUb/8/GDVG0SBwKFadwV27dxqUwbah9rKPbj/M7 r5XuUMd/ZNnsw== From: sashiko-bot@kernel.org Subject: Re: [PATCH v6 32/33] KVM: s390: arm64: Implement basic page fault handler Reply-To: sashiko-reviews@lists.linux.dev To: "Steffen Eiden" Cc: "Heiko Carstens" , "Alexander Gordeev" , "Oliver Upton" , "Christian Borntraeger" , "Marc Zyngier" , linux-s390@vger.kernel.org, kvmarm@lists.linux.dev, kvm@vger.kernel.org, "Vasily Gorbik" In-Reply-To: <20260812153631.3376090-33-seiden@linux.ibm.com> References: <20260812153631.3376090-1-seiden@linux.ibm.com> <20260812153631.3376090-33-seiden@linux.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Wed, 12 Aug 2026 16:34:54 +0000 Message-Id: <20260812163454.AEE411F00A3E@smtp.kernel.org> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Thank you for your contribution! Sashiko AI review found 1 potential issue(= s) to consider: - [High] Guest-triggerable KVM_BUG on unexpected program interrupt codes (P= ICs) causes host denial of service. -- --- Patch [32]: [PATCH v6 32/33] KVM: s390: arm64: Implement basic page fau= lt handler --- commit 1cc2a3fc0641697d83c316659559bcf0aaa389a1 Author: Steffen Eiden KVM: s390: arm64: Implement basic page fault handler Add host functionality to page in guest memory. If the guest does something unexpected or illegal exit to userspace abort guest execution. > diff --git a/arch/s390/kvm/arm64/mmu.c b/arch/s390/kvm/arm64/mmu.c > new file mode 100644 > index 0000000000000..71cd582f24ff8 > --- /dev/null > +++ b/arch/s390/kvm/arm64/mmu.c [ ... ] > +static int kvm_handle_pic(struct kvm_vcpu *vcpu, bool *translation) > +{ > + switch (kvm_vcpu_fault_pic(vcpu)) { > + /* expected cases: */ > + case PGM_ASCE_TYPE: > + case PGM_REGION_FIRST_TRANS: > + case PGM_REGION_SECOND_TRANS: > + case PGM_REGION_THIRD_TRANS: > + case PGM_SEGMENT_TRANSLATION: > + case PGM_PAGE_TRANSLATION: > + *translation =3D true; > + break; > + case PGM_PROTECTION: > + break; > + /* unexpected cases: */ > + case 0: > + KVM_BUG(1, vcpu->kvm, "On MMU fault path but no fault occurred"); [Severity: High] Does this KVM_BUG() allow a guest to trigger a host warning? If a guest performs an action that triggers a hardware exit with an unexpected program interrupt code (like an alignment fault that exits with pic =3D=3D 0), kvm_handle_pic() falls into these branches. Since KVM_BUG() expands to a WARN_ONCE in the host kernel, this could cause a host kernel panic on systems configured with panic_on_warn. Should this cleanly return -EFAULT to userspace to gracefully abort the guest without asserting instead? > + return -EFAULT; > + default: > + KVM_BUG(1, vcpu->kvm, "Unexpected program interrupt 0x%x, TEID 0x%016l= x", > + vcpu->arch.sae_block.hai.pic, vcpu->arch.sae_block.hai.teid.val); > + send_sig(SIGSEGV, current, 0); > + return -EFAULT; > + } > + > + return 0; > +} --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20260812153631.3376= 090-1-seiden@linux.ibm.com?part=3D32