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 311B53F327D; Tue, 11 Aug 2026 14:44:59 +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=1786459503; cv=none; b=PFVddZJBgbdJN4C1k32RteQnSQVcFlbv5Z0aI5MdMTpe6zt6Z1PeIH4PqnlcvG6SgHDvpPsEml7x3pAMhjbS2AOjZJEKQr2PZqemqLXDlBGEufVFVxJb19D51FRljEa0sgbwN7pYusBNyOMMkKamBfHJ4kWc3S6MKbuwWY3WWs8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786459503; c=relaxed/simple; bh=/LPEH55R6LClPqeXnYARvDZU8XDKgr9ZBtZUHbi7ZdM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=r2Ga09EtuVPZmuoOKnLKhbmTgsvDk0UGIiT3UzFS5BkAHv/ffX/OmfNVzso5LH87rZ2lNeXhrRnS372m3IQXug3eqyIE1OkdW07OJvdYWcRqgo/6elI5ECLYKNIexuvMtwN5foOoqduTfTK+iTtMBgyGZirH3iTYCVJJzvMaD2k= 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=UhMkyTJN; 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="UhMkyTJN" 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> 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: <20260803134403.80630-8-steven.price@arm.com> 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