On Wed, 5 Feb 2020 11:48:42 +0100
Christian Borntraeger <borntraeger@xxxxxxxxxx> wrote:
> On 05.02.20 10:51, Thomas Huth wrote:
> > On 03/02/2020 14.19, Christian Borntraeger wrote:
> >> From: Michael Mueller <mimu@xxxxxxxxxxxxx>
> >>
> >> The patch implements interruption injection for the following
> >> list of interruption types:
> >>
> >> - I/O
> >> __deliver_io (III)
> >>
> >> - External
> >> __deliver_cpu_timer (IEI)
> >> __deliver_ckc (IEI)
> >> __deliver_emergency_signal (IEI)
> >> __deliver_external_call (IEI)
> >>
> >> - cpu restart
> >> __deliver_restart (IRI)
> >>
> >> The service interrupt is handled in a followup patch.
> >>
> >> Signed-off-by: Michael Mueller <mimu@xxxxxxxxxxxxx>
> >> Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
> >> [fixes]
> >> ---
> >> arch/s390/include/asm/kvm_host.h | 8 +++
> >> arch/s390/kvm/interrupt.c | 93 ++++++++++++++++++++++----------
> >> 2 files changed, 74 insertions(+), 27 deletions(-)
> >>
> >> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> >> index a45d10d87a8a..989cea7a5591 100644
> >> --- a/arch/s390/include/asm/kvm_host.h
> >> +++ b/arch/s390/include/asm/kvm_host.h
> >> @@ -563,6 +563,14 @@ enum irq_types {
> >> #define IRQ_PEND_MCHK_MASK ((1UL << IRQ_PEND_MCHK_REP) | \
> >> (1UL << IRQ_PEND_MCHK_EX))
> >>
> >> +#define IRQ_PEND_MCHK_REP_MASK (1UL << IRQ_PEND_MCHK_REP)
> >> +
> >> +#define IRQ_PEND_EXT_II_MASK ((1UL << IRQ_PEND_EXT_CPU_TIMER) | \
> >> + (1UL << IRQ_PEND_EXT_CLOCK_COMP) | \
> >> + (1UL << IRQ_PEND_EXT_EMERGENCY) | \
> >> + (1UL << IRQ_PEND_EXT_EXTERNAL) | \
> >> + (1UL << IRQ_PEND_EXT_SERVICE))
> >> +
> >> struct kvm_s390_interrupt_info {
> >> struct list_head list;
> >> u64 type;
> >> diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
> >> index c06c89d370a7..ecdec6960a60 100644
> >> --- a/arch/s390/kvm/interrupt.c
> >> +++ b/arch/s390/kvm/interrupt.c
> >> @@ -387,6 +387,12 @@ static unsigned long deliverable_irqs(struct kvm_vcpu *vcpu)
> >> __clear_bit(IRQ_PEND_EXT_SERVICE, &active_mask);
> >> if (psw_mchk_disabled(vcpu))
> >> active_mask &= ~IRQ_PEND_MCHK_MASK;
> >> + /* PV guest cpus can have a single interruption injected at a time. */
> >> + if (kvm_s390_pv_is_protected(vcpu->kvm) &&
> >> + vcpu->arch.sie_block->iictl != IICTL_CODE_NONE)
> >> + active_mask &= ~(IRQ_PEND_EXT_II_MASK |
> >> + IRQ_PEND_IO_MASK |
> >> + IRQ_PEND_MCHK_REP_MASK);
> >
> > I don't quite understand why there is a difference between
> > IRQ_PEND_MCHK_REP and IRQ_PEND_MCHK_EX here? Why not simply use
> > IRQ_PEND_MCHK_MASK here? Could you elaborate? (and maybe add a sentence
> > to the patch description)
>
> I added that part.
> My idea was that an exigent machine check would be kind of fatal that it can override
> the previous interrupt. Now we do not implement the override (kill the previous interrupt)
> so I agree, maybe lets use IRQ_PEND_MCHK_MASK
This makes me wonder about interrupt priorities in general. Under which
circumstances can we have an interrupt with a lower priority already
injected (but not delivered) in the injection area when a
higher-priority interrupt comes along? I'm a bit confused here.
