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 2E9EDC5B56A for ; Tue, 11 Aug 2026 14:45:18 +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=3E9gzrqUSmsxtPYO1SMTzKKoyneSbVUSG4Bik/QNVSA=; b=LzrkSjT6x3tLNFCwx9ooKT2upt +LT02P6kuI4Haoemu+Bm0N7dtb5bIg/vWqwn1aNOi/27HgyLX/VNeLiWbJZhm6ZWbKNrP2t/Zct2V Uz1ZWkrXnJBXqoFCGvP146BV2IiR91asLCmAy4q2xW+184Z7/h+kw5b0n0VW4nPbc/65usTyuUJ7W JpDTdmqtNEpUioH+vyf6tNegrQXfpb+D1/2iTYwWlPlFaPzm7QK9+4xvvhvPwVpWYM+sONt/+AhdS 3TM/F6g2F8rmlDTKAtyUPz9CC5KBx0j3whwwselEmSv1a6X76JKCwCi51eYMuNABJ7ViYC7Vy8x73 rGPrNfxQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wtniy-0000000EFBv-1PG8; Tue, 11 Aug 2026 14:45:04 +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 1wtniv-0000000EFBD-0Nzj for linux-arm-kernel@lists.infradead.org; Tue, 11 Aug 2026 14:45:02 +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 E97BB1682; Tue, 11 Aug 2026 07:44:54 -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 EF9DA3F86F; Tue, 11 Aug 2026 07:44:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1786459498; bh=/LPEH55R6LClPqeXnYARvDZU8XDKgr9ZBtZUHbi7ZdM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=UhMkyTJN6nwQPPoHojp2Lj90fCxYgfZoPQnlFeUfUA7QykLZDiF4BKo9sc5b4f8Cu tgVMWQsawjcyUgRgg0Bm7XS/nBDFtj0Sesm5suAVALsIGilMsDyBy47x0YNQEeI5bh 5ONfXUPbgnRx3kWP8wbSZ0K3W95SrAy0Gy8N9cpw= Date: Tue, 11 Aug 2026 15:44:53 +0100 From: Catalin Marinas To: Steven Price Cc: kvm@vger.kernel.org, kvmarm@lists.linux.dev, Marc Zyngier , Will Deacon , James Morse , Oliver Upton , Suzuki K Poulose , Zenghui Yu , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Joey Gouly , Alexandru Elisei , Christoffer Dall , Fuad Tabba , linux-coco@lists.linux.dev, Ganapatrao Kulkarni , Gavin Shan , Shanker Donthineni , Alper Gun , "Aneesh Kumar K . V" , Emi Kisanuki , Vishal Annapurve , WeiLin.Chang@arm.com, Lorenzo Pieralisi Subject: Re: [PATCH v16 07/45] arm64: mm: Handle Granule Protection Faults (GPFs) Message-ID: References: <20260803134403.80630-1-steven.price@arm.com> <20260803134403.80630-8-steven.price@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260803134403.80630-8-steven.price@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260811_074501_261856_45EABFD0 X-CRM114-Status: GOOD ( 22.63 ) 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 Mon, Aug 03, 2026 at 02:43:23PM +0100, Steven Price wrote: > 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. > > Reviewed-by: Suzuki K Poulose > Reviewed-by: Gavin Shan > Signed-off-by: Steven Price > --- > 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 | 28 ++++++++++++++++++++++------ > 1 file changed, 22 insertions(+), 6 deletions(-) > > diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c > index 85e23388f9bb..ea3ae0ca7dba 100644 > --- a/arch/arm64/mm/fault.c > +++ b/arch/arm64/mm/fault.c > @@ -909,6 +909,22 @@ static int do_tag_check_fault(unsigned long far, unsigned long esr, > return 0; > } > > +static int do_gpf_ptw(unsigned long far, unsigned long esr, struct pt_regs *regs) > +{ > + const struct fault_info *inf = esr_to_fault_info(esr); > + > + die_kernel_fault(inf->name, far, esr, regs); > + return 0; > +} > + > +static int do_gpf(unsigned long far, unsigned long esr, struct pt_regs *regs) > +{ > + if (!is_el1_instruction_abort(esr) && fixup_exception(regs, esr)) > + return 0; > + > + return 1; > +} Is there a valid case for fixup_exception() here? IOW, do we ever have a valid user mapping of the pages delegated to a guest? If the above is considered a kernel bug, I'd not silently ignore this (like return less bytes copied or -EFAULT to user) but rather warn, potentially rate-limited. If there is a real use-case for this, what's preventing GUP + memcpy() from triggering a similar fault with no fixup available? -- Catalin