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 A994C4C10ED for ; Thu, 1 Oct 2026 09:47:08 +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=1790848031; cv=none; b=a/ne284efImbAw9WsAU60LdRibWvgua2x9ETO7U4Oylbqdw4LpAJxv4Cm/qW6VKdCqqWyfNxxVXZfRUzBxTDLVJb/K1QMvc5eNSQnnXNY415YrCB4CVlmEZqJ8qt0hkju1EzHaBnn0TrFWd/XPLZYw++UgJXWj7KYC1hBet6NIY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790848031; c=relaxed/simple; bh=/QIsZj5ZknEUJbqRrL7io4YJRt6LKVatf9W0JsU0gc0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Bcz87Y4srf8306cIRZbJIMsZ0qSxM17RYfaFBFcV0FLigtzcv2pTgKH9sYmiVFWg2jSZe8pqubPB90YTJaQURZluZ9MwtRnx0ZXGu0q39DeIC38hbllKJDG5u5aP0+MgiveMwY8KKuQARLlDJoCSbQSGBsxfi44G4wbo0f+wiro= 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; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=C3YuSdKb; 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 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="C3YuSdKb" 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 9271F497; Thu, 1 Oct 2026 02:47:04 -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 369363F86F; Thu, 1 Oct 2026 02:47:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1790848028; bh=/QIsZj5ZknEUJbqRrL7io4YJRt6LKVatf9W0JsU0gc0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=C3YuSdKbRNRrJeKGiTX+MeAWFYw1nMoNgLQPuFYsOKCffatmtgLArZDDicLEn5IVN QdfadJ+CTSkMVLbzp8x6wGpUaXAex+pC4OdZCR998yLM9QY0S0Of+W+nz/hvtSi8a0 Y4FJRvpIK78QwNVq7zTFGk0de+v9hV5E84NrS3R8= Date: Thu, 1 Oct 2026 10:47:03 +0100 From: Catalin Marinas To: Suzuki K Poulose Cc: linux-arm-kernel@lists.infradead.org, will@kernel.org, linux-kernel@vger.kernel.org, steven.price@arm.com, gshan@redhat.com, aneesh.kumar@kernel.org, maz@kernel.org, oupton@kernel.org, tabba@google.com, mark.rutland@arm.com, linux-coco@lists.linux.dev Subject: Re: [PATCH v19] arm64: mm: Handle Granule Protection Faults (GPFs) Message-ID: References: <20260930164930.1388438-1-suzuki.poulose@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260930164930.1388438-1-suzuki.poulose@arm.com> On Wed, Sep 30, 2026 at 05:49:30PM +0100, Suzuki K Poulose wrote: > From: Steven Price > > If the host attempts to access granules that have been delegated to RMM > (for use as an RMM object or Realm Data), 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: > > * Userspace having access to a page which has been delegated. We don't allow > mapping a delegated page (which may have Realm VM private data) to EL0. > But if we do encounter this, trigger a SIGBUS to allow debugging > > * A kernel mode access is even more serious, except for the cases where : > - Benign overreads e.g. load_unaligned_zeropad(), we should be able to fix > this up. > - A kdump kernel trying to access delegated page (donated by the primary > kernel). We do not support this yet, but can be added in the later series. > > There is ongoing work to unmap the guest_memfd backed private pages > from the linear map. We would additionally need to unmap the other > delegated pages too. For now handle the GPF and only fixing up kernel mode > accesses via kernel VA (which would cover both the legitimate cases above) > > Reviewed-by: Gavin Shan > Signed-off-by: Steven Price > Signed-off-by: Suzuki K Poulose > --- > Changes since v18: > * Only fixup accesses via kernel VA > 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 > 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 | 35 +++++++++++++++++++++++++++++------ > 1 file changed, 29 insertions(+), 6 deletions(-) > > diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c > index 75c3e463df2ef..ded9288a5dd2f 100644 > --- a/arch/arm64/mm/fault.c > +++ b/arch/arm64/mm/fault.c > @@ -914,6 +914,29 @@ 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); > + unsigned long addr = untagged_addr(far); > + > + die_kernel_fault(inf->name, addr, esr, regs); > + return 0; > +} > + > +static int do_gpf(unsigned long far, unsigned long esr, struct pt_regs *regs) > +{ > + /* > + * Userspace must not have a delegated page mapped in. If the kernel > + * is made to access it, then we have a serious problem. > + * Only fixup if the access came via kernel VA. e.g., load_unaligned_zeropad() > + */ > + if (!user_mode(regs) && !is_el1_instruction_abort(esr) && > + !is_ttbr0_addr(untagged_addr(far)) && fixup_exception(regs, esr)) > + return 0; > + > + return 1; > +} The logic looks fine to me, so: Reviewed-by: Catalin Marinas Whether we want to unmap the delegated pages eventually (and not just guest_memfd), given that we get a synchronous fault architecturally, I'm not yet convinced it's worth it (it fragments the linear map). -- Catalin