Steven Price <steven.price@xxxxxxx> writes:
> 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.
>
A non-page walk fault can also be caused by host kernel trying to access a
page which it had delegated before. It would be nice to dump details
like FAR in that case. Right now it shows only the below.
[ 285.122310] Internal error: Granule Protection Fault not on table walk: 0000000096000068 [#1] PREEMPT SMP
[ 285.122427] Modules linked in:
[ 285.122512] CPU: 1 UID: 0 PID: 217 Comm: kvm-vcpu-0 Not tainted 6.12.0-rc1-00082-g8461d8333829 #42
[ 285.122656] Hardware name: FVP Base RevC (DT)
[ 285.122733] pstate: 81400009 (Nzcv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)
[ 285.122871] pc : clear_page+0x18/0x50
[ 285.122975] lr : kvm_gmem_get_pfn+0xbc/0x190
[ 285.123110] sp : ffff800082cef900
[ 285.123182] x29: ffff800082cef910 x28: 0000000090000000 x27: 0000000090000006
.....
-aneesh
>
> Signed-off-by: Steven Price <steven.price@xxxxxxx>
> ---
> 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 8b281cf308b3..f9d72a936d48 100644
> --- a/arch/arm64/mm/fault.c
> +++ b/arch/arm64/mm/fault.c
> @@ -804,6 +804,25 @@ 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" },
> @@ -840,12 +859,12 @@ 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" },
> { 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" },
> --
> 2.34.1
