From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id E4D87C98307 for ; Wed, 23 Sep 2026 11:06:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=jw7cdKPvhQqCHfyfU5u17nrqt6E9Q3a8TKdmkl3BqS4=; b=kjXi1A+Q5PogNdm6qZYPXJD7+Y f6A1z5N7XNhmc/5//qhYU04zmMdWXFjmDYOEo/i0IZlz4qcSOISDXZtgONMYq91O84BVhbnfYgd4Z QtYXiFNJBpfhkAcgWOcGXI12cvzn5KzKmGiXKFElglc7fr3y+FLRSddh7KTpUokA3Z+JmrYaFvWzW 3AZxVZ+ytYRyRrRnvqoCGrBjgY/KBfDvg97ZIhbm0SJHf1Hh6uRY9xrSc+S5EDHGcgJDrdZs0vUab xHk5yeUS/Vqs+T5v1jvyzZ4Nf2n5WqtPcHo8cjN5Iy/X+S+/YvAztWjlkmL+sp7uTdHpZzIB+PpQm Nh3FFmEA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x9Knw-00000007zYt-2KLi; Wed, 23 Sep 2026 11:06:24 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x9Knu-00000007zXt-2M6W for linux-arm-kernel@lists.infradead.org; Wed, 23 Sep 2026 11:06:23 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 06D531516; Wed, 23 Sep 2026 04:06:17 -0700 (PDT) Received: from arm.com (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id F314F3F86F; Wed, 23 Sep 2026 04:06:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1790161580; bh=AiLb+XIqqeogh5YIbkCt/ug3YDrQxWlGcnRvc7/OSzg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=RZd6PDCElzn8tIotWwrvT9WVNfhaf+E0nsTzPz7biVZvPKwP8gDLv/16qknBwwCeE XZqVX7rtPhnEOmnIpGuocfxi5mPtjFIoFr3VFosboC1I/0xJVnx9XIJolkmsXAj5+B BQkCyZnQEJkrsTacXF5+UJGQn1YF7TiEHuz/UsaY= Date: Wed, 23 Sep 2026 12:06:15 +0100 From: Catalin Marinas To: Will Deacon Cc: Suzuki K Poulose , kvm@vger.kernel.org, kvmarm@lists.linux.dev, maz@kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, steven.price@arm.com, aneesh.kumar@kernel.org, oupton@kernel.org, gshan@redhat.com, joey.gouly@arm.com, tabba@google.com, yuzenghui@huawei.com, linux-coco@lists.linux.dev, gankulkarni@os.amperecomputing.com, sdonthineni@nvidia.com, alpergun@google.com, fj0570is@fujitsu.com, WeiLin.Chang@arm.com, lpieralisi@kernel.org, enju.kohei@fujitsu.com Subject: Re: [PATCH v18] arm64: mm: Handle Granule Protection Faults (GPFs) Message-ID: References: <20260913070459.2547407-1-suzuki.poulose@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260923_040622_691760_A10D4B71 X-CRM114-Status: GOOD ( 29.19 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Sep 22, 2026 at 06:15:34PM +0100, Will Deacon wrote: > On Sun, Sep 13, 2026 at 08:04:58AM +0100, Suzuki K Poulose wrote: > > From: Steven Price > > > > If the host attempts to access granules that have been delegated for use > > in a realm these accesses will be caught and will trigger a Granule > > Protection Fault (GPF). > > > > A fault during a page walk signals a bug in the kernel and is handled by > > oopsing the kernel. A non-page walk fault could be caused by user space > > having access to a page which has been delegated to the kernel and will > > trigger a SIGBUS to allow debugging why user space is trying to access a > > delegated page. > > > > There is work in progress to unmap the guest_memfd backed private pages from the > > linear map. Until we get that support, we could get spurious GPFs from within > > the kernel, e.g., load_unaligned_zeropad(). So, try to fix them up for now. > > > > Reviewed-by: Suzuki K Poulose > > Reviewed-by: Gavin Shan > > Reviewed-by: Catalin Marinas > > Signed-off-by: Steven Price > > Signed-off-by: Suzuki K Poulose > > --- > > Changes since v17: > > * Pass untagged address to die_kernel_fault() - Sashiko > > * Explicitly check !user_mode() for fixups - Catalin > > * Switch to BUS_OBJERR for si_code from SI_KERNEL - Catalin > > * Clarify the commit description about the upcoming work on > > unmapping guest_memfd backed pages from linear map > > Changes since v16: > > * Update the commit description to indicate why we try to fixup GPFs > > Changes since v10: > > * Don't call arm64_notify_die() in do_gpf() but simply return 1. > > Changes since v2: > > * Include missing "Granule Protection Fault at level -1" > > --- > > arch/arm64/mm/fault.c | 30 ++++++++++++++++++++++++------ > > 1 file changed, 24 insertions(+), 6 deletions(-) > > I still don't think we should do this, given that the plan is to unmap > the memory from the linear map. If this thing fires, it's a kernel bug > and it should be fatal. If the linear unmapping gets merged first, I agree, no need to handle these faults. I haven't followed that series, so no idea where it is at. However, I'd still keep part of this patch - the reporting and panic but without the actual exception table recovery. There's some value in killing user-space and WARN (or pr_ratelimited) without a full panic, it helps with debugging. That's what do_bad() via arm64_notify_die() gives us currently anyway. So maybe we can keep it to just: static int do_gpf(unsigned long far, unsigned long esr, struct pt_regs *regs) { if (user_mode(regs)) { pr_alert_ratelimited("%s[%d]: granule protection fault at 0x%016lx\n", current->comm, task_pid_nr(current), untagged_addr(far)); mem_abort_decode(esr); } return 1; } and we get the SIGBUS or panic via do_mem_abort(). No recovery for uaccess though, we get the same kernel panic. -- Catalin