Re: [PATCH 3/3] pvpanic : update pvpanic spec document

[Peter Maydell]

On Fri, 18 Dec 2020 at 13:36, Mihai Carabas <mihai.carabas@oracle.com> wrote:
>
> Add pvpanic PCI device support details in docs/specs/pvpanic.txt.
>
> Signed-off-by: Mihai Carabas <mihai.carabas@oracle.com>
> ---
>  docs/specs/pvpanic.txt | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/docs/specs/pvpanic.txt b/docs/specs/pvpanic.txt
> index a90fbca..5ddc8df 100644
> --- a/docs/specs/pvpanic.txt
> +++ b/docs/specs/pvpanic.txt
> @@ -1,7 +1,7 @@
>  PVPANIC DEVICE
>  ==============
>
> -pvpanic device is a simulated ISA device, through which a guest panic
> +pvpanic device is a simulated device, through which a guest panic
>  event is sent to qemu, and a QMP event is generated. This allows
>  management apps (e.g. libvirt) to be notified and respond to the event.
>
> @@ -9,6 +9,9 @@ The management app has the option of waiting for 
> GUEST_PANICKED events,
>  and/or polling for guest-panicked RunState, to learn when the pvpanic
>  device has fired a panic event.
>
> +The pvpanic device can be implemented as an ISA device (using IOPORT) or as a
> +PCI device.
> +
>  ISA Interface
>  -------------
>
> @@ -24,6 +27,14 @@ bit 1: a guest panic has happened and will be handled by 
> the guest;
>         the host should record it or report it, but should not affect
>         the execution of the guest.
>
> +PCI Interface
> +-------------
> +
> +The PCI interface is similar to the ISA interface except that it uses an MMIO
> +address space provided by its BAR0, 2 bytes long. Any machine with a PCI
> +device can enable a pvpanic device by adding '-device pvpanic-pci' to the
> +command line.

Why is it 2 bytes long, when both the ISA and the ACPI interfaces are
only a single byte? What size reads and writes are accepted?

thanks
-- PMM