From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: From: Cornelia Huck In-Reply-To: <20211111185812.2326093-2-eperezma@redhat.com> References: <20211111185812.2326093-1-eperezma@redhat.com> <20211111185812.2326093-2-eperezma@redhat.com> Date: Fri, 12 Nov 2021 11:34:57 +0100 Message-ID: <87sfw1oe5q.fsf@redhat.com> MIME-Version: 1.0 Subject: [virtio-dev] Re: [PATCH v3 1/2] content: Explain better the status clearing bits Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable To: Eugenio =?utf-8?Q?P=C3=A9rez?= , virtio-dev@lists.oasis-open.org, virtio-comment@lists.oasis-open.org, mst@redhat.com, jasowang@redhat.com Cc: amikheev@nvidia.com, stefanha@redhat.com, shahafs@nvidia.com, oren@nvidia.com, pasic@linux.ibm.com, bodong@nvidia.com, "Dr . David Alan Gilbert" , parav@nvidia.com, mgurtovoy@nvidia.com List-ID: On Thu, Nov 11 2021, Eugenio P=C3=A9rez 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 I think MMIO uses that mechanism as well? > 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 P=C3=A9rez > --- > 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-initializ= e. > +The driver MUST NOT clear ACKNOWLEDGE, DRIVER, DRIVER_OK, FEATURES_OK or > +DEVICE_NEEDS_RESET bits of \field{device status}, except if resetting th= e whole > +device. If the driver sets the FAILED bit, the driver MUST later reset = the > +device before attempting to re-initialize. I think we need to distinguish "driver wants to clear a status bit" from "driver is initiating a reset, and that transport implements that by writing 0 to the device status". So, what about "The driver MUST NOT clear a \field{device status} bit, except when setting \field{device status} to 0 as a transport-specific way to intitiate a reset." If we introduce driver-clearable bits later, we can simply make that "The driver MUST NOT clear a \field{device status} bit other than NEW_BIT, ..." --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org