Re: [Qemu-devel] [RFC v4 6/9] vfio: add 'x-aer' option to disable aer capability

[Alex Williamson <alex.williamson@redhat.com>]

On Mon, 2015-03-02 at 15:16 +0800, Chen Fan wrote:
> add 'x-aer' option to disable aer capability if user
> want.

I'm generally one to favor using the x- flag, but we need to figure out
if we need to make this be a supported option or not.  We also need to
decide whether we should include your previous patch that toggled this
support based on machine type.  We don't care about migration
compatibility, but users might depend on specific error behavior and we
don't want to break that for existing machine types.  This would include
only the q35 machine types through QEMU 2.3, I believe.

My impression is that it should probably be supported.  There may be
cases where the guest OS does not support AER and we want to be able to
invoke the old vm_stop() behavior.


> Signed-off-by: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
> ---
>  hw/vfio/pci.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> index db4ba23..5471437 100644
> --- a/hw/vfio/pci.c
> +++ b/hw/vfio/pci.c
> @@ -156,6 +156,8 @@ typedef struct VFIOPCIDevice {
>      uint32_t features;
>  #define VFIO_FEATURE_ENABLE_VGA_BIT 0
>  #define VFIO_FEATURE_ENABLE_VGA (1 << VFIO_FEATURE_ENABLE_VGA_BIT)
> +#define VFIO_FEATURE_ENABLE_AER_BIT 1
> +#define VFIO_FEATURE_ENABLE_AER (1 << VFIO_FEATURE_ENABLE_AER_BIT)

Bit 1 is already taken by:

47cbe50 vfio-pci: Enable device request notification support

>      int32_t bootindex;
>      uint8_t pm_cap;
>      bool has_vga;
> @@ -2728,6 +2730,10 @@ static int vfio_setup_aer(VFIOPCIDevice *vdev, uint8_t cap_ver,
>      uint32_t severity;
>      int ret;
>  
> +    if (!(vdev->features & VFIO_FEATURE_ENABLE_AER)) {
> +        return 0;
> +    }
> +
>      pdev->exp.aer_log.log_max = PCIE_AER_LOG_MAX_DEFAULT;
>      ret = pcie_aer_init(pdev, cap_ver, pos, size);
>      if (ret) {
> @@ -3569,6 +3575,8 @@ static Property vfio_pci_dev_properties[] = {
>                         intx.mmap_timeout, 1100),
>      DEFINE_PROP_BIT("x-vga", VFIOPCIDevice, features,
>                      VFIO_FEATURE_ENABLE_VGA_BIT, false),
> +    DEFINE_PROP_BIT("x-aer", VFIOPCIDevice, features,
> +                    VFIO_FEATURE_ENABLE_AER_BIT, true),
>      DEFINE_PROP_INT32("bootindex", VFIOPCIDevice, bootindex, -1),
>      /*
>       * TODO - support passed fds... is this necessary?