Re: [qemu-s390x] [PATCH] s390x/pci: add common fmb

[Cornelia Huck]

On Tue,  4 Sep 2018 17:15:49 +0800
Yi Min Zhao <address@hidden> wrote:

> Common function measurement block is used to report counters of
> successfully issued pcilg/stg/stb and rpcit instructions. This patch
> introduces a new struct ZpciFmb and schedules a timer callback to
> copy fmb to the guest memory at a interval time which is set to
> 4s by default. While attemping to update fmb failed, an event error
> would be generated. After pcilg/stg/stb and rpcit interception
> handlers issue successfully, increase the related counter. The guest
> could pass null address to switch off FMB and stop corresponding
> timer.

Hard to review without documentation, but some comments below.

> 
> Signed-off-by: Yi Min Zhao <address@hidden>
> Reviewed-by: Pierre Morel<address@hidden>
> ---
>  hw/s390x/s390-pci-bus.c  |   3 +-
>  hw/s390x/s390-pci-bus.h  |  24 +++++++++++
>  hw/s390x/s390-pci-inst.c | 105 
> +++++++++++++++++++++++++++++++++++++++++++++--
>  hw/s390x/s390-pci-inst.h |   1 +
>  4 files changed, 129 insertions(+), 4 deletions(-)

(...)

> diff --git a/hw/s390x/s390-pci-inst.c b/hw/s390x/s390-pci-inst.c
> index 7b61367ee3..1ed5cb91d0 100644
> --- a/hw/s390x/s390-pci-inst.c
> +++ b/hw/s390x/s390-pci-inst.c

> @@ -456,6 +457,10 @@ int pcilg_service_call(S390CPU *cpu, uint8_t r1, uint8_t 
> r2, uintptr_t ra)
>          return 0;
>      }
>  
> +    if (pbdev->fmb_addr) {
> +        pbdev->fmb.ld_ops++;
> +    }

As fmb is a part of the structure, just update it unconditionally?
You'll only copy it to the guest if measurements are active anyway.

> +
>      env->regs[r1] = data;
>      setcc(cpu, ZPCI_PCI_LS_OK);
>      return 0;

(...)

> @@ -889,6 +905,63 @@ void pci_dereg_ioat(S390PCIIOMMU *iommu)
>      iommu->g_iota = 0;
>  }
>  
> +void fmb_timer_free(S390PCIBusDevice *pbdev)
> +{
> +    if (pbdev->fmb_timer) {
> +        timer_del(pbdev->fmb_timer);
> +        timer_free(pbdev->fmb_timer);
> +        pbdev->fmb_timer = NULL;
> +    }
> +    pbdev->fmb_addr = 0;
> +    memset(&pbdev->fmb, 0, sizeof(ZpciFmb));

Maybe move clearing the buffer to before you enable measurements
instead? (Needed to make my suggestion above work correctly.)

> +}
> +
> +static int fmb_do_update(S390PCIBusDevice *pbdev, uint8_t offset, int len)
> +{
> +    MemTxResult ret;
> +
> +    ret = address_space_write(&address_space_memory,
> +                              pbdev->fmb_addr + (uint64_t)offset,
> +                              MEMTXATTRS_UNSPECIFIED,
> +                              (uint8_t *)&pbdev->fmb + offset,
> +                              len);
> +    if (ret) {
> +        s390_pci_generate_error_event(ERR_EVENT_FMBA, pbdev->fh, pbdev->fid,
> +                                      pbdev->fmb_addr, 0);
> +        fmb_timer_free(pbdev);

So, failure to update the guest-provided area is supposed to disable
measurements?

> +    }
> +
> +    return ret;
> +}
> +
> +static void fmb_update(void *opaque)
> +{
> +    S390PCIBusDevice *pbdev = opaque;
> +    int64_t t = qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
> +    uint8_t offset = offsetof(ZpciFmb, last_update);
> +
> +    /* Update U bit */
> +    pbdev->fmb.last_update |= UPDATE_U_BIT;
> +    if (fmb_do_update(pbdev, offset, sizeof(uint64_t))) {
> +        return;
> +    }
> +
> +    /* Update FMB counters */
> +    pbdev->fmb.sample++;
> +    if (fmb_do_update(pbdev, 0, sizeof(ZpciFmb))) {
> +        return;
> +    }
> +
> +    /* Clear U bit and update the time */
> +    pbdev->fmb.last_update = time2tod(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL));
> +    pbdev->fmb.last_update &= ~UPDATE_U_BIT;
> +    if (fmb_do_update(pbdev, offset, sizeof(uint64_t))) {
> +        return;
> +    }
> +
> +    timer_mod(pbdev->fmb_timer, t + DEFAULT_MUI);
> +}
> +
>  int mpcifc_service_call(S390CPU *cpu, uint8_t r1, uint64_t fiba, uint8_t ar,
>                          uintptr_t ra)
>  {
> @@ -1018,9 +1091,35 @@ int mpcifc_service_call(S390CPU *cpu, uint8_t r1, 
> uint64_t fiba, uint8_t ar,
>              s390_set_status_code(env, r1, ZPCI_MOD_ST_SEQUENCE);
>          }
>          break;
> -    case ZPCI_MOD_FC_SET_MEASURE:
> -        pbdev->fmb_addr = ldq_p(&fib.fmb_addr);
> +    case ZPCI_MOD_FC_SET_MEASURE: {
> +        uint64_t fmb_addr = ldq_p(&fib.fmb_addr);
> +
> +        if (fmb_addr & FMBK_MASK) {
> +            cc = ZPCI_PCI_LS_ERR;
> +            s390_pci_generate_error_event(ERR_EVENT_FMBPRO, pbdev->fh,
> +                                          pbdev->fid, fmb_addr, 0);
> +            fmb_timer_free(pbdev);
> +            break;
> +        }
> +
> +        if (!fmb_addr) {
> +            /* Stop updating FMB. */
> +            fmb_timer_free(pbdev);
> +            break;
> +        }
> +
> +        pbdev->fmb_addr = fmb_addr;
> +        if (!pbdev->fmb_timer) {
> +            pbdev->fmb_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL,
> +                                            fmb_update, pbdev);
> +        } else if (timer_pending(pbdev->fmb_timer)) {
> +            /* Remove pending timer to update FMB address. */
> +            timer_del(pbdev->fmb_timer);
> +        }

So, setting fmb_addr to another address will not reset the counters,
but just cause the blocks to be stored into a different address?

> +        timer_mod(pbdev->fmb_timer,
> +                  qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + DEFAULT_MUI);
>          break;
> +    }
>      default:
>          s390_program_interrupt(&cpu->env, PGM_OPERAND, 6, ra);
>          cc = ZPCI_PCI_LS_ERR;