Re: [Qemu-devel] [PATCH v5] s390x/pci: add common function measurement block

[Cornelia Huck <cohuck@redhat.com>]

On Wed, 19 Dec 2018 13:57:05 +0100
Pierre Morel <pmorel@linux.ibm.com> wrote:

> From: Yi Min Zhao <zyimin@linux.ibm.com>
> 
> Common function measurement block is used to report zPCI internal
> counters of successful pcilg/stg/stb and rpcit instructions to
> a memory location provided by the program.
> 
> This patch introduces a new ZpciFmb structure and schedules a timer
> callback to copy the zPCI measures to the FMB in the guest memory
> at an interval time set to 4s.
> 
> An error while attemping to update the FMB, would generate an error
> event to the guest.
> 
> The pcilg/stg/stb and rpcit interception handlers increase the
> related counter on a successful call.
> The guest shall pass a null FMBA (FMB address) in the FIB (Function
> Information Block) when it issues a Modify PCI Function Control
> instruction to switch off FMB and stop the corresponding timer.
> 
> Signed-off-by: Yi Min Zhao <zyimin@linux.ibm.com>
> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> ---
>  hw/s390x/s390-pci-bus.c  |   4 +-
>  hw/s390x/s390-pci-bus.h  |  29 +++++++++++
>  hw/s390x/s390-pci-inst.c | 129 +++++++++++++++++++++++++++++++++++++++++++++--
>  hw/s390x/s390-pci-inst.h |   1 +
>  4 files changed, 159 insertions(+), 4 deletions(-)
> 

> +static void fmb_update(void *opaque)
> +{
> +    S390PCIBusDevice *pbdev = opaque;
> +    int64_t t = qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
> +    int i;
> +
> +    /* Update U bit */
> +    pbdev->fmb.last_update *= 2;
> +    pbdev->fmb.last_update |= UPDATE_U_BIT;
> +    if (fmb_do_update(pbdev, offsetof(ZpciFmb, last_update),
> +                      pbdev->fmb.last_update, sizeof(uint64_t))) {

Uh... the size of the last_update field would make more sense here...
Also for the other fields below. Is there a reason that does not work?

> +        return;
> +    }
> +
> +    /* Update FMB sample count */
> +    if (fmb_do_update(pbdev, offsetof(ZpciFmb, sample),
> +                      pbdev->fmb.sample++, sizeof(uint32_t))) {
> +        return;
> +    }
> +
> +    /* Update FMB counters */
> +    for (i = 0; i < ZPCI_FMB_CNT_MAX; i++) {
> +        if (fmb_do_update(pbdev, offsetof(ZpciFmb, counter[i]),
> +                          pbdev->fmb.counter[i], sizeof(uint64_t))) {
> +            return;
> +        }
> +    }
> +
> +    /* Clear U bit and update the time */
> +    pbdev->fmb.last_update = time2tod(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL));
> +    pbdev->fmb.last_update *= 2;
> +    if (fmb_do_update(pbdev, offsetof(ZpciFmb, last_update),
> +                      pbdev->fmb.last_update, sizeof(uint64_t))) {
> +        return;
> +    }
> +    timer_mod(pbdev->fmb_timer, t + DEFAULT_MUI);
> +}
> +