Benjamin Herrenschmidt <b...@kernel.crashing.org> writes:
> On POWER9 and bad paste instruction (targeting the wrong memory
> type) or an invalid opcode in an AMO (atomic memory operation)
> will result in specific DSISR bits to be set.
>
> We currently don't understand those bits and thus just "hang"
> the process taking constant page faults.
>
> Additionally in the case of paste, it appears that we don't
> always get a valid DAR value when the error is a wrong memory
> type.
>
> So we need to test those errors early in do_page_fault(),
> I chose to generate a SIGBUS which is more correct than a SIGSEGV.
This is true even for hash right ? If so do we want to update
do_hash_page:
#ifdef CONFIG_PPC_STD_MMU_64
andis. r0,r4,0xa450 /* weird error? */
bne- handle_page_fault /* if not, try to insert a HPTE */
that 0xa450 such that we add these errors and call hand_page_fault in
case of these DSISR values ?
>
> Signed-off-by: Benjamin Herrenschmidt <b...@kernel.crashing.org>
> ---
>
> diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
> index 0266c664014a..5dfce2022f74 100644
> --- a/arch/powerpc/mm/fault.c
> +++ b/arch/powerpc/mm/fault.c
> @@ -337,6 +337,21 @@ int do_page_fault(struct pt_regs *regs, unsigned long
> address,
> }
> #endif /* CONFIG_PPC_ICSWX */
>
> +#ifdef CONFIG_PPC_STD_MMU_64
> + /*
> + * These faults indicate a copy/paste on an invalid memory type
> + * or an incorrect AMO operation. They have been observed as not
> + * properly updating the DAR, so handle them early
> + */
> + if (error_code & (DSISR_BAD_COPYPASTE | DSISR_BAD_AMO)) {
> + if (user_mode(regs))
> + _exception(SIGBUS, regs, BUS_OBJERR, address);
> + else
> + rc = SIGBUS;
> + goto bail;
> + }
> +#endif /* CONFIG_PPC_STD_MMU_64 */
> +
> if (notify_page_fault(regs))
> goto bail;
>
> diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
> index 7e50e47375d6..71f524f2b109 100644
> --- a/arch/powerpc/include/asm/reg.h
> +++ b/arch/powerpc/include/asm/reg.h
> @@ -282,6 +282,8 @@
> #define DSISR_UNSUPP_MMU 0x00080000 /* Unsupported MMU config */
> #define DSISR_SET_RC 0x00040000 /* Failed setting of
> R/C bits */
> #define DSISR_PGDIRFAULT 0x00020000 /* Fault on page directory */
> +#define DSISR_BAD_COPYPASTE 0x00000008 /* Copy/Paste on wrong mem
> type */
> +#define DSISR_BAD_AMO 0x00000004 /* Incorrect AMO opcode
> */
> #define SPRN_TBRL 0x10C /* Time Base Read Lower Register (user, R/O) */
> #define SPRN_TBRU 0x10D /* Time Base Read Upper Register (user, R/O) */
> #define SPRN_CIR 0x11B /* Chip Information Register (hyper, R/0) */
-aneesh
