linux-kernel - Re: [PATCH v2 04/43] arm64: RME: Handle Granule Protection Faults (GPFs)

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Date: Tue, 16 Apr 2024 12:17:06 +0100
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Steven Price <steven.price@....com>, kvm@...r.kernel.org,
 kvmarm@...ts.linux.dev
Cc: Catalin Marinas <catalin.marinas@....com>, Marc Zyngier <maz@...nel.org>,
 Will Deacon <will@...nel.org>, James Morse <james.morse@....com>,
 Oliver Upton <oliver.upton@...ux.dev>, Zenghui Yu <yuzenghui@...wei.com>,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 Joey Gouly <joey.gouly@....com>, Alexandru Elisei
 <alexandru.elisei@....com>, Christoffer Dall <christoffer.dall@....com>,
 Fuad Tabba <tabba@...gle.com>, linux-coco@...ts.linux.dev,
 Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>
Subject: Re: [PATCH v2 04/43] arm64: RME: Handle Granule Protection Faults
 (GPFs)

On 12/04/2024 09:42, 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.
> 
> Signed-off-by: Steven Price <steven.price@....com>
> ---
>   arch/arm64/mm/fault.c | 29 ++++++++++++++++++++++++-----
>   1 file changed, 24 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> index 8251e2fea9c7..91da0f446dd9 100644
> --- a/arch/arm64/mm/fault.c
> +++ b/arch/arm64/mm/fault.c
> @@ -765,6 +765,25 @@ 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;
> +}
> +
> +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))
> +		return 0;
> +
> +	arm64_notify_die(inf->name, regs, inf->sig, inf->code, far, esr);
> +	return 0;
> +}
> +
>   static const struct fault_info fault_info[] = {
>   	{ do_bad,		SIGKILL, SI_KERNEL,	"ttbr address size fault"	},
>   	{ do_bad,		SIGKILL, SI_KERNEL,	"level 1 address size fault"	},
> @@ -802,11 +821,11 @@ static const struct fault_info fault_info[] = {
>   	{ do_alignment_fault,	SIGBUS,  BUS_ADRALN,	"alignment fault"		},
>   	{ do_bad,		SIGKILL, SI_KERNEL,	"unknown 34"			},
>   	{ do_bad,		SIGKILL, SI_KERNEL,	"unknown 35"			},

Should this also be converted to do_gpf_ptw, "GPF at level -1", given we 
support LPA2 ?


> -	{ do_bad,		SIGKILL, SI_KERNEL,	"unknown 36"			},
> -	{ do_bad,		SIGKILL, SI_KERNEL,	"unknown 37"			},
> -	{ do_bad,		SIGKILL, SI_KERNEL,	"unknown 38"			},
> -	{ do_bad,		SIGKILL, SI_KERNEL,	"unknown 39"			},
> -	{ do_bad,		SIGKILL, SI_KERNEL,	"unknown 40"			},
> +	{ do_gpf_ptw,		SIGKILL, SI_KERNEL,	"Granule Protection Fault at level 0" },
> +	{ do_gpf_ptw,		SIGKILL, SI_KERNEL,	"Granule Protection Fault at level 1" },
> +	{ do_gpf_ptw,		SIGKILL, SI_KERNEL,	"Granule Protection Fault at level 2" },
> +	{ do_gpf_ptw,		SIGKILL, SI_KERNEL,	"Granule Protection Fault at level 3" },
> +	{ do_gpf,		SIGBUS,  SI_KERNEL,	"Granule Protection Fault not on table walk" },
>   	{ do_bad,		SIGKILL, SI_KERNEL,	"level -1 address size fault"	},
>   	{ do_bad,		SIGKILL, SI_KERNEL,	"unknown 42"			},
>   	{ do_translation_fault,	SIGSEGV, SEGV_MAPERR,	"level -1 translation fault"	},


Rest looks fine to me.

Suzuki