Re: [PATCH v3 1/2] content: Explain better the status clearing bits

[Jason Wang <jasowang@redhat.com>]

On Fri, Nov 12, 2021 at 2:59 AM Eugenio PÃrez <eperezma@redhat.com> wrote:
>
> The spec tells that "The driver MUST NOT clear a device status bit", but
> a device using PCI transport reset a virtio device writing 0 to device
> status. In some way, that is to clear all its bits.
>
> Instead of add an exception, tell explicitely the status bits that
> the driver cannot clear anytime in a normal operation, so conformant
> device and drivers keeps being conformant.
>
> Signed-off-by: Eugenio PÃrez <eperezma@redhat.com>
> ---
>  content.tex | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/content.tex b/content.tex
> index 5d112af..2aa3006 100644
> --- a/content.tex
> +++ b/content.tex
> @@ -60,9 +60,10 @@ \section{\field{Device Status} Field}\label{sec:Basic Facilities of a Virtio Dev
>  initialization sequence specified in
>  \ref{sec:General Initialization And Device Operation / Device
>  Initialization}.
> -The driver MUST NOT clear a
> -\field{device status} bit.  If the driver sets the FAILED bit,
> -the driver MUST later reset the device before attempting to re-initialize.
> +The driver MUST NOT clear ACKNOWLEDGE, DRIVER, DRIVER_OK, FEATURES_OK or
> +DEVICE_NEEDS_RESET bits of \field{device status}, except if resetting the whole
> +device.

Any reason for using blacklist here? I guess it is used for patch 2
(introduce the bit that can be cleared?).

Thanks

> If the driver sets the FAILED bit, the driver MUST later reset the
> +device before attempting to re-initialize.
>
>  The driver SHOULD NOT rely on completion of operations of a
>  device if DEVICE_NEEDS_RESET is set.
> --
> 2.27.0
>