[PATCH v14 03/44] arm64: RME: Handle Granule Protection Faults (GPFs)

[Steven Price]

On 21/05/2026 13:25, Marc Zyngier wrote:
> On Wed, 13 May 2026 14:17:11 +0100,
> Steven Price <steven.price at arm.com> 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 <suzuki.poulose at arm.com>
>> Reviewed-by: Gavin Shan <gshan at redhat.com>
>> Signed-off-by: Steven Price <steven.price at arm.com>
>> ---
>> 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 0f3c5c7ca054..6358ea4787ba 100644
>> --- a/arch/arm64/mm/fault.c
>> +++ b/arch/arm64/mm/fault.c
>> @@ -905,6 +905,22 @@ 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;
>> +}
>> +
>>  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"	},
>> @@ -941,12 +957,12 @@ static const struct fault_info fault_info[] = {
>>  	{ do_bad,		SIGKILL, SI_KERNEL,	"unknown 32"			},
>>  	{ do_alignment_fault,	SIGBUS,  BUS_ADRALN,	"alignment fault"		},
>>  	{ do_bad,		SIGKILL, SI_KERNEL,	"unknown 34"			},
>> -	{ do_bad,		SIGKILL, SI_KERNEL,	"unknown 35"			},
>> -	{ 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 -1" },
>> +	{ 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" },
> 
> It wouldn't hurt to align the textual description with what we have
> for other fault syndromes:
> 
> 	"level X granule protection fault (translation table walk)"
> 
> for the PTW-trigger faults, and
> 
> 	"granule protection fault"
> 
> for the non PTW case.

Sure, no problem.

Thanks,
Steve

> 
> Thanks,
> 
> 	M.
>