RE: [PATCH v12 05/10] pci: add admin vq registers to virtio over pci

[Parav Pandit <parav@nvidia.com>]

> From: Max Gurtovoy <mgurtovoy@nvidia.com>
> Sent: Wednesday, April 26, 2023 5:12 PM
> 
> On 25/04/2023 1:14, Parav Pandit wrote:
> >
> >
> > On 4/24/2023 6:06 PM, Max Gurtovoy wrote:
> >
> >>> +If VIRTIO_F_ADMIN_VQ has been negotiated, and if the driver
> >>> +configures any administration virtqueues, the driver MUST configure
> >>> +the administration virtqueues using the index in the range
> >>> +\field{admin_queue_index} to \field{admin_queue_index} +
> >>> +\field{admin_queue_num} - 1 inclusive.
> >>> +The driver MAY configure less administration virtqueues than
> >>> +supported by the device.
> >>
> >> we need to say something about other virtq's indexes.
> >> For example, if aq index = 0 then for the vblk device the request
> >> queues would start from index = 1.
> >>
> >> can we address this ?
> >
> > It may slightly complicate the device implementation when device
> > dynamically changes the VQ indices based on the negotiation of the
> > feature bit.
> > Also the drivers with and without need a different VQ index handling.
> >
> > I am thinking that aq index should not overlap with the vq index in
> > range exposed by num_queues field.
> >
> > This also aligns to the exclusion of aq count from num_queues field.
> 
> The namespace of the aq and other vq index is the same.
> And the configuration is done using the same queue_select and other registers.
> Thus, we need to address the above comment otherwise all the device
> virtqueues chapters are wrong.

Michael has added below line in this patch in num_queues description so it covers the exclusion part.

+        This excludes administration virtqueues if any are supported.

I inspected all the devices.
Following devices which has multi queue supports are fine, net, console, scsi host, gpu, input, crypto, socket, rpmb, iommu, sound, scmi, gpio. 

Following single q devices are fine too: entropy, mem ballon dev, mem, i2c, pmem.
So mostly all chapters donât look wrong.

Block device needs below change.
WDYT?

From 0592d167451280bc212df7322077f4c94b28c917 Mon Sep 17 00:00:00 2001
From: Parav Pandit <parav@nvidia.com>
Date: Thu, 27 Apr 2023 01:01:41 +0300
Subject: [PATCH] virtio-blk: Rename num_queues to num_req_queues

num_queues field represents number of blk specific request queues.

Renaming it to num_req_queues reflect its precise usage.
It also avoids confusion with PCI transport's generic num_queues field.

Signed-off-by: Parav Pandit <parav@nvidia.com>
---
 device-types/blk/description.tex | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/device-types/blk/description.tex b/device-types/blk/description.tex
index f04c932..5a27399 100644
--- a/device-types/blk/description.tex
+++ b/device-types/blk/description.tex
@@ -16,7 +16,7 @@ \subsection{Virtqueues}\label{sec:Device Types / Block Device / Virtqueues}
 \end{description}

  N=1 if VIRTIO_BLK_F_MQ is not negotiated, otherwise N is set by
- \field{num_queues}.
+ \field{num_req_queues}.

 \subsection{Feature bits}\label{sec:Device Types / Block Device / Feature bits}

@@ -108,7 +108,7 @@ \subsection{Device configuration layout}\label{sec:Device Types / Block Device /
         } topology;
         u8 writeback;
         u8 unused0;
-        u16 num_queues;
+        u16 num_req_queues;
         le32 max_discard_sectors;
         le32 max_discard_seg;
         le32 discard_sector_alignment;
@@ -135,8 +135,8 @@ \subsection{Device configuration layout}\label{sec:Device Types / Block Device /
 present. The availability of the others all depend on various feature
 bits as indicated above.

-The field \field{num_queues} only exists if VIRTIO_BLK_F_MQ is set. This field specifies
-the number of queues.
+The field \field{num_req_queues} only exists if VIRTIO_BLK_F_MQ is set. This field specifies
+the number of request queues.

 The parameters in the configuration space of the device \field{max_discard_sectors}
 \field{discard_sector_alignment} are expressed in 512-byte units if the
--
2.26.2