Re: [Qemu-devel] [PATCH] virtio-pci: Add Function Level Reset support

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Aug 07, 2019 at 10:22:41AM +0200, Julia Suvorova wrote:
> Using FLR becomes convenient in cases where resetting the bus is
> impractical, for example, when debugging the behavior of individual
> functions.
> 
> Signed-off-by: Julia Suvorova <jusual@redhat.com>
> ---
>  hw/virtio/virtio-pci.c | 10 ++++++++++
>  hw/virtio/virtio-pci.h |  1 +
>  2 files changed, 11 insertions(+)
> 
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index f6d2223e78..37c5d6efbc 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -599,6 +599,10 @@ static void virtio_write_config(PCIDevice *pci_dev, uint32_t address,
>  
>      pci_default_write_config(pci_dev, address, val, len);
>  
> +    if (proxy->has_flr) {
> +        pcie_cap_flr_write_config(pci_dev, address, val, len);
> +    }
> +
>      if (range_covers_byte(address, len, PCI_COMMAND) &&
>          !(pci_dev->config[PCI_COMMAND] & PCI_COMMAND_MASTER)) {
>          virtio_pci_stop_ioeventfd(proxy);
> @@ -1718,6 +1722,8 @@ static void virtio_pci_realize(PCIDevice *pci_dev, Error **errp)
>      proxy->notify_pio.size = 0x4;
>      proxy->notify_pio.type = VIRTIO_PCI_CAP_NOTIFY_CFG;
>  
> +    proxy->has_flr = false;
> +
>      /* subclasses can enforce modern, so do this unconditionally */
>      memory_region_init(&proxy->modern_bar, OBJECT(proxy), "virtio-pci",
>                         /* PCI BAR regions must be powers of 2 */
> @@ -1749,6 +1755,10 @@ static void virtio_pci_realize(PCIDevice *pci_dev, Error **errp)
>  
>          pci_dev->exp.pm_cap = pos;
>  
> +        /* Set Function Level Reset capability bit */
> +        pcie_cap_flr_init(pci_dev);
> +        proxy->has_flr = true;
> +
>          /*
>           * Indicates that this function complies with revision 1.2 of the
>           * PCI Power Management Interface Specification.


I don't think we can set this for everyone: this will break
things like cross version migration.



> diff --git a/hw/virtio/virtio-pci.h b/hw/virtio/virtio-pci.h
> index 292275acb1..16d293a6bf 100644
> --- a/hw/virtio/virtio-pci.h
> +++ b/hw/virtio/virtio-pci.h
> @@ -152,6 +152,7 @@ struct VirtIOPCIProxy {
>      VirtIOIRQFD *vector_irqfd;
>      int nvqs_with_notifiers;
>      VirtioBusState bus;
> +    bool has_flr;
>  };
>  
>  static inline bool virtio_pci_modern(VirtIOPCIProxy *proxy)



> -- 
> 2.21.0