Re: [kvm-unit-tests PATCH v1 2/2] lib: s390x: better smp interrupt checks

Janosch Frank
2022-06-10T09:43:41Z

On 6/3/22 17:40, Claudio Imbrenda wrote:
> Use per-CPU flags and callbacks for Program, Extern, and I/O interrupts
> instead of global variables.
>
> This allows for more accurate error handling; a CPU waiting for an
> interrupt will not have it "stolen" by a different CPU that was not
> supposed to wait for one, and now two CPUs can wait for interrupts at
> the same time.
>
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> ---
> lib/s390x/asm/arch_def.h | 7 ++++++-
> lib/s390x/interrupt.c | 38 ++++++++++++++++----------------------
> 2 files changed, 22 insertions(+), 23 deletions(-)
>
> diff --git a/lib/s390x/asm/arch_def.h b/lib/s390x/asm/arch_def.h
> index 72553819..3a0d9c43 100644
> --- a/lib/s390x/asm/arch_def.h
> +++ b/lib/s390x/asm/arch_def.h
> @@ -124,7 +124,12 @@ struct lowcore {
> uint8_t pad_0x0280[0x0308 - 0x0280]; /* 0x0280 */
> uint64_t sw_int_crs[16]; /* 0x0308 */
> struct psw sw_int_psw; /* 0x0388 */
> - uint8_t pad_0x0310[0x11b0 - 0x0398]; /* 0x0398 */
> + uint32_t pgm_int_expected; /* 0x0398 */
> + uint32_t ext_int_expected; /* 0x039c */
> + void (*pgm_cleanup_func)(void); /* 0x03a0 */
> + void (*ext_cleanup_func)(void); /* 0x03a8 */
> + void (*io_int_func)(void); /* 0x03b0 */
> + uint8_t pad_0x03b8[0x11b0 - 0x03b8]; /* 0x03b8 */

Before we directly pollute the lowcore I'd much rather have a pointer to
a struct. We could then either use any area of the lowcore by adding a
union or we extend the SMP lib per-cpu structs.

I don't want to have to review offset calculations for every change of
per-cpu data. They are just way too easy to get wrong.