From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id E592F2D77E4; Mon, 15 Sep 2025 10:55:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757933732; cv=none; b=RzpXfDa5KGmbE+MdI254qF6p1xe6c5xn46skCHQ5ESPLm5VV+FeE2fqPAs+4WlBOMiFkPLZRX2uOYCe6RWNrqaloJDAqV91G6jvWTaoY2NoXtk40r4cC0+mJTzyJQnD34oKd7Ih0TVFs35j6h80E28fWyFnWsQlCn3MjiMbp7hg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757933732; c=relaxed/simple; bh=b2mf4Z3CF2NmHVs2TZP+YQo6OPUtx5t0zbzVahIcsKk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=bMSrZkYj2jwWP8a2d/vwsmVtQqlbr4dImrlQVhOWH1o2hdTkKwmWaWm+3HEdK8zCtvikYKQc5N9DsyL+D94P5ljQQ0ms5DvIEjq8wwLTaOmEgYfa9ifV0Rfjaw2pfNoAPpF3PvPHNoFnfvh6Il1zjhCEfdh9/MUDLaWEk3adKVs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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 020F21BF7; Mon, 15 Sep 2025 03:55:22 -0700 (PDT) Received: from [10.57.5.5] (unknown [10.57.5.5]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E6C5D3F694; Mon, 15 Sep 2025 03:55:24 -0700 (PDT) Message-ID: Date: Mon, 15 Sep 2025 11:55:22 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v10 02/43] arm64: RME: Handle Granule Protection Faults (GPFs) To: Catalin Marinas 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 References: <20250820145606.180644-1-steven.price@arm.com> <20250820145606.180644-3-steven.price@arm.com> From: Steven Price Content-Language: en-GB In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 29/08/2025 12:38, Catalin Marinas wrote: > On Wed, Aug 20, 2025 at 03:55:22PM +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 v2: >> * Include missing "Granule Protection Fault at level -1" >> --- >> arch/arm64/mm/fault.c | 31 +++++++++++++++++++++++++------ >> 1 file changed, 25 insertions(+), 6 deletions(-) >> >> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c >> index d816ff44faff..e4237637cd8f 100644 >> --- a/arch/arm64/mm/fault.c >> +++ b/arch/arm64/mm/fault.c >> @@ -854,6 +854,25 @@ 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; >> +} > > This is fine, it's irrelevant whether the fault happened at EL0 or EL1. > >> +static int do_gpf(unsigned long far, unsigned long esr, struct pt_regs *regs) >> +{ >> + const struct fault_info *inf = esr_to_fault_info(esr); >> + >> + if (!is_el1_instruction_abort(esr) && fixup_exception(regs, esr)) >> + return 0; >> + >> + arm64_notify_die(inf->name, regs, inf->sig, inf->code, far, esr); >> + return 0; >> +} > > The end result is somewhat similar but why not just return 1 and avoid > the arm64_notify_die() call? Let do_mem_abort() handle the oops vs user > signal. With die_kernel_fault() we print the "Unable to handle > kernel..." message and some more information. > Yes, that makes sense - something has gone very wrong if the kernel hits a GPF but that's no reason not to output a (more) useful message. Thanks, Steve