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

[Claudio Imbrenda <imbrenda@linux.ibm.com>]

On Mon, 27 Jun 2022 11:28:18 +0200
Janosch Frank <frankja@linux.ibm.com> wrote:

> 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.

not currently, but it's useful to have in lib

should I split this into a separate patch?

> 
> > +
> >   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];

it's equivalent, do you have a reason for changing it?

> 
> >   
> >   	/* 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  
>