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 03CC2C98304 for ; Wed, 23 Sep 2026 15:45:51 +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=xBhwM6wbqAw5a+cVNgYvlXlXJxCKVG4pNRvbUVKP8IA=; b=ufN+aSMSfZr8nNdSOJDOKTWecY OTqWOR69LbUBSxIIFTVN7ultWFOnQMVn9AZdx7xEFnWY3LyoGE9rGbks0r0bbGO2hMx1oGEij8ZDJ LMApT3rl+2t8tRb17x2IFTr97KVEI0bbnhqno9ji3Zw/J/WKbJxPLaAnLDO8fBTH8k4ZMD0Wbinfa VKyjI3C2iffDPD6SWYUgO22tk3tcPUZr3Ia1LCg8UIiwhsie1oxh0qA4bs1VSegbrqZCCmKlhhKrT QVVlPtJyZ6r+l010rc3J8Vs4hYG+p+/+aBugjw7U5E5qhW3bwlX8v8y7VIsZYz8piwnhWgNwf/SQG nXFIvj3w==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x9PAG-00000008nJc-3mAG; Wed, 23 Sep 2026 15:45:44 +0000 Received: from sea.source.kernel.org ([2600:3c0a:e001:78e:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1x9PAG-00000008nJQ-03QB for linux-arm-kernel@lists.infradead.org; Wed, 23 Sep 2026 15:45:44 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id C160340D91; Wed, 23 Sep 2026 15:45:43 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7B5741F00893; Wed, 23 Sep 2026 15:45:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790178343; bh=xBhwM6wbqAw5a+cVNgYvlXlXJxCKVG4pNRvbUVKP8IA=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=KapfSIupahzymrJQOac0ZZru85avmkuCFsYN2BBX6hl8axXNJnffgnyqlm+GAqWFQ xzT7HNgoPLukmPtZQiUBGjAAgsMTd8mBODvU/qvqBoVlLs8WPfPnrRxVZn6ihew8bP vmmMP0HpYQBzSv0xarrSJFoDT0NNFmAVaJN5trYsm/T8kdBaP69tAOT9Jceqe5C9/t LV8Gui+KCanV+FtQ1aix6tIz7u0R/FbAIq7lEskqqpVMZDrB8GsXpeMSh9MekmkAQ3 7ZMPHiPPDsji0EEtsNO5GjhuQJSJsjKHq/vLBxDvftss4APctbzOGdwKH6KmH4FoDW ATZpPB7e1lFyQ== Date: Wed, 23 Sep 2026 16:45:36 +0100 From: Will Deacon To: Catalin Marinas 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-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 Wed, Sep 23, 2026 at 12:06:15PM +0100, Catalin Marinas wrote: > 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. But how can this ever occur in user mode? I'm fine with making that part unconditional. Will