Re: [kvm-unit-tests PATCH v2 3/3] lib: s390x: better smp interrupt checks

Janosch Frank
2022-06-27T09:28:38Z

On 6/24/22 16:45, Claudio Imbrenda wrote:
> Use per-CPU flags and callbacks for Program and Extern 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.
>
> This will significantly improve error reporting and debugging when
> things go wrong.
>
> Both program interrupts and extern interrupts are now CPU-bound, even
> though some extern interrupts are floating (notably, the SCLP
> interrupt). In those cases, the testcases should mask interrupts and/or
> expect them appropriately according to need.
>
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> ---
> lib/s390x/asm/arch_def.h | 17 +++++++++++-
> lib/s390x/smp.h | 8 +-----
> lib/s390x/interrupt.c | 57 +++++++++++++++++++++++++++++-----------
> lib/s390x/smp.c | 11 ++++++++
> 4 files changed, 70 insertions(+), 23 deletions(-)
[...]
>
> +struct lowcore *smp_get_lowcore(uint16_t idx)
> +{
> + if (THIS_CPU->idx == idx)
> + return &lowcore;
> +
> + check_idx(idx);
> + return cpus[idx].lowcore;
> +}

This function is unused.

> +
> int smp_sigp(uint16_t idx, uint8_t order, unsigned long parm, uint32_t *status)
> {
> check_idx(idx);
> @@ -253,6 +262,7 @@ static int smp_cpu_setup_nolock(uint16_t idx, struct psw psw)
>
> /* Copy all exception psws. */
> memcpy(lc, cpus[0].lowcore, 512);
> + lc->this_cpu = cpus + idx;

Why not:
lc->this_cpu = &cpus[idx];

>
> /* Setup stack */
> cpus[idx].stack = (uint64_t *)alloc_pages(2);
> @@ -325,6 +335,7 @@ void smp_setup(void)
> for (i = 0; i < num; i++) {
> cpus[i].addr = entry[i].address;
> cpus[i].active = false;
> + cpus[i].idx = i;
> /*
> * Fill in the boot CPU. If the boot CPU is not at index 0,
> * swap it with the one at index 0. This guarantees that the