Re: [PATCH V3 13/22] vfio-pci: cpr part 2

[Steven Sistare]

On 5/21/2021 6:24 PM, Alex Williamson wrote:
> On Fri,  7 May 2021 05:25:11 -0700
> Steve Sistare <steven.sistare@oracle.com> wrote:
> 
>> Finish cpr for vfio-pci by preserving eventfd's and vector state.
>>
>> Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
>> ---
>>  hw/vfio/pci.c | 110 
>> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
>>  1 file changed, 108 insertions(+), 2 deletions(-)
>>
>> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
>> index f7ac9f03..e983db4 100644
>> --- a/hw/vfio/pci.c
>> +++ b/hw/vfio/pci.c
>> @@ -2661,6 +2661,27 @@ static void vfio_put_device(VFIOPCIDevice *vdev)
>>      vfio_put_base_device(&vdev->vbasedev);
>>  }
>>  
>> +static void setenv_event_fd(VFIOPCIDevice *vdev, int nr, const char *name,
>> +                            EventNotifier *ev)
>> +{
>> +    char envname[256];
>> +    int fd = event_notifier_get_fd(ev);
>> +    const char *vfname = vdev->vbasedev.name;
>> +
>> +    if (fd >= 0) {
>> +        snprintf(envname, sizeof(envname), "%s_%s_%d", vfname, name, nr);
>> +        setenv_fd(envname, fd);
>> +    }
>> +}
>> +
>> +static int getenv_event_fd(VFIOPCIDevice *vdev, int nr, const char *name)
>> +{
>> +    char envname[256];
>> +    const char *vfname = vdev->vbasedev.name;
>> +    snprintf(envname, sizeof(envname), "%s_%s_%d", vfname, name, nr);
>> +    return getenv_fd(envname);
>> +}
>> +
>>  static void vfio_err_notifier_handler(void *opaque)
>>  {
>>      VFIOPCIDevice *vdev = opaque;
>> @@ -2692,7 +2713,13 @@ static void vfio_err_notifier_handler(void *opaque)
>>  static void vfio_register_err_notifier(VFIOPCIDevice *vdev)
>>  {
>>      Error *err = NULL;
>> -    int32_t fd;
>> +    int32_t fd = getenv_event_fd(vdev, 0, "err");
> 
> Arg order should match the actual env names, device name, interrupt
> name, interrupt number.

I am happy to swap interrupt name and interrupt order, here and in 
setenv_event_fd().
However, I pass vdev so the getenv_event_fd() caller does not need to generate 
the env 
var name, and the details of the name are confined to {get,set}_event_fd.  I 
could pass 
the vdev name instead, but IMO it would be uglier at every call site, eg:

    fd = getenv_event_fd(vdev->vbasedev.name, "err", 0);
vs
    fd = getenv_event_fd(vdev, "err", 0);

I could rename the functions so they do not imply argument similarity with 
getenv_fd:
  getenv_event_fd --> save_event_fd
  setenv_event_fd --> load_event_fd

>> +    if (fd >= 0) {
>> +        event_notifier_init_fd(&vdev->err_notifier, fd);
>> +        qemu_set_fd_handler(fd, vfio_err_notifier_handler, NULL, vdev);
>> +        return;
>> +    }
>>  
>>      if (!vdev->pci_aer) {
>>          return;
>> @@ -2753,7 +2780,14 @@ static void vfio_register_req_notifier(VFIOPCIDevice 
>> *vdev)
>>      struct vfio_irq_info irq_info = { .argsz = sizeof(irq_info),
>>                                        .index = VFIO_PCI_REQ_IRQ_INDEX };
>>      Error *err = NULL;
>> -    int32_t fd;
>> +    int32_t fd = getenv_event_fd(vdev, 0, "req");
>> +
>> +    if (fd >= 0) {
>> +        event_notifier_init_fd(&vdev->req_notifier, fd);
>> +        qemu_set_fd_handler(fd, vfio_req_notifier_handler, NULL, vdev);
>> +        vdev->req_enabled = true;
>> +        return;
>> +    }
>>  
>>      if (!(vdev->features & VFIO_FEATURE_ENABLE_REQ)) {
>>          return;
>> @@ -3286,12 +3320,82 @@ static Property vfio_pci_dev_properties[] = {
>>      DEFINE_PROP_END_OF_LIST(),
>>  };
>>  
>> +static int vfio_pci_pre_save(void *opaque)
>> +{
>> +    VFIOPCIDevice *vdev = opaque;
>> +    int i;
>> +
>> +    for (i = 0; i < vdev->nr_vectors; i++) {
>> +        VFIOMSIVector *vector = &vdev->msi_vectors[i];
>> +        if (vector->use) {
>> +            setenv_event_fd(vdev, i, "interrupt", &vector->interrupt);
>> +            if (vector->virq >= 0) {
>> +                setenv_event_fd(vdev, i, "kvm_interrupt",
>> +                                &vector->kvm_interrupt);
>> +            }
>> +        }
>> +    }
>> +    setenv_event_fd(vdev, 0, "err", &vdev->err_notifier);
>> +    setenv_event_fd(vdev, 0, "req", &vdev->req_notifier);
>> +    return 0;
>> +}
>> +
>> +static void vfio_claim_vectors(VFIOPCIDevice *vdev, int nr_vectors, bool 
>> msix)
>> +{
>> +    int i, fd;
>> +    bool pending = false;
>> +    PCIDevice *pdev = &vdev->pdev;
>> +
>> +    vdev->nr_vectors = nr_vectors;
>> +    vdev->msi_vectors = g_new0(VFIOMSIVector, nr_vectors);
>> +    vdev->interrupt = msix ? VFIO_INT_MSIX : VFIO_INT_MSI;
>> +
>> +    for (i = 0; i < nr_vectors; i++) {
>> +        VFIOMSIVector *vector = &vdev->msi_vectors[i];
>> +
>> +        fd = getenv_event_fd(vdev, i, "interrupt");
>> +        if (fd >= 0) {
>> +            vfio_vector_init(vdev, i, fd);
>> +            qemu_set_fd_handler(fd, vfio_msi_interrupt, NULL, vector);
>> +        }
>> +
>> +        fd = getenv_event_fd(vdev, i, "kvm_interrupt");
>> +        if (fd >= 0) {
>> +            vfio_add_kvm_msi_virq(vdev, vector, i, msix, fd);
>> +        }
>> +
>> +        if (msix && msix_is_pending(pdev, i) && msix_is_masked(pdev, i)) {
>> +            set_bit(i, vdev->msix->pending);
>> +            pending = true;
>> +        }
>> +    }
>> +
>> +    if (msix) {
>> +        memory_region_set_enabled(&pdev->msix_pba_mmio, pending);
>> +    }
>> +}
>> +
>>  static int vfio_pci_post_load(void *opaque, int version_id)
>>  {
>>      VFIOPCIDevice *vdev = opaque;
>>      PCIDevice *pdev = &vdev->pdev;
>> +    int nr_vectors;
>>      bool enabled;
>>  
>> +    if (msix_enabled(pdev)) {
>> +        nr_vectors = vdev->msix->entries;
>> +        vfio_claim_vectors(vdev, nr_vectors, true);
>> +        msix_init_vector_notifiers(pdev, vfio_msix_vector_use,
>> +                                   vfio_msix_vector_release, NULL);
>> +
>> +    } else if (msi_enabled(pdev)) {
>> +        nr_vectors = msi_nr_vectors_allocated(pdev);
>> +        vfio_claim_vectors(vdev, nr_vectors, false);
>> +
>> +    } else if (vfio_pci_read_config(pdev, PCI_INTERRUPT_PIN, 1)) {
>> +        error_report("vfio_pci_post_load does not support INTX");
>> +    }
> 
> Why?  Is post-load where we really want to find this out?  Thanks,

This is also checked at VM creation time if only-cpr-capable is specified.
I could also check it in vfio_pci_pre_save.

- Steve

>> +
>>      pdev->reused = false;
>>      enabled = pci_get_word(pdev->config + PCI_COMMAND) & PCI_COMMAND_MASTER;
>>      memory_region_set_enabled(&pdev->bus_master_enable_region, enabled);
>> @@ -3310,8 +3414,10 @@ static const VMStateDescription vfio_pci_vmstate = {
>>      .version_id = 0,
>>      .minimum_version_id = 0,
>>      .post_load = vfio_pci_post_load,
>> +    .pre_save = vfio_pci_pre_save,
>>      .needed = vfio_pci_needed,
>>      .fields = (VMStateField[]) {
>> +        VMSTATE_MSIX(pdev, VFIOPCIDevice),
>>          VMSTATE_END_OF_LIST()
>>      }
>>  };
>