From 07d1c765d4cdd345e63cd77504a38646c2a0f015 Mon Sep 17 00:00:00 2001
From: Bruce Leidl <bruce@subgraph.com>
Date: Wed, 11 Sep 2019 15:53:02 -0400
Subject: [PATCH] allow configuring size of virtio queues

---
 rust/src/virtio/bus.rs    | 20 ++++++++++++++++----
 rust/src/virtio/config.rs | 11 +++++------
 2 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/rust/src/virtio/bus.rs b/rust/src/virtio/bus.rs
index e665796..1b8e36d 100644
--- a/rust/src/virtio/bus.rs
+++ b/rust/src/virtio/bus.rs
@@ -6,6 +6,7 @@ use super::{VirtioDevice,VirtioDeviceOps,PciIrq};
 use super::consts::*;
 use super::pci::PciBus;
 use crate::vm::Result;
+use std::iter;
 
 
 pub struct VirtioBus {
@@ -43,7 +44,7 @@ pub struct VirtioDeviceConfig<'a> {
     kvm: Kvm,
     ops: Arc<RwLock<dyn VirtioDeviceOps>>,
     mmio: AddressRange,
-    num_queues: usize,
+    queue_sizes: Vec<usize>,
     config_size: usize,
     device_class: u16,
     features: u64,
@@ -61,7 +62,7 @@ impl <'a> VirtioDeviceConfig<'a> {
             kvm,
             ops,
             mmio,
-            num_queues: 0,
+            queue_sizes: Vec::new(),
             config_size: 0,
             features: 0,
             device_class: 0x0880,
@@ -100,7 +101,11 @@ impl <'a> VirtioDeviceConfig<'a> {
     }
 
     pub fn num_queues(&self) -> usize {
-        self.num_queues
+        self.queue_sizes.len()
+    }
+
+    pub fn queue_sizes(&self) -> &[usize] {
+        &self.queue_sizes
     }
 
     #[allow(dead_code)]
@@ -108,8 +113,15 @@ impl <'a> VirtioDeviceConfig<'a> {
         self.config_size
     }
 
+    pub fn set_queue_sizes(&mut self, sizes: &[usize]) -> &'a mut VirtioDeviceConfig {
+        self.queue_sizes.clear();
+        self.queue_sizes.extend_from_slice(sizes);
+        self
+    }
+
     pub fn set_num_queues(&mut self, n: usize) -> &'a mut VirtioDeviceConfig {
-        self.num_queues = n;
+        self.queue_sizes.clear();
+        self.queue_sizes.extend(iter::repeat(DEFAULT_QUEUE_SIZE as usize).take(n));
         self
     }
 
diff --git a/rust/src/virtio/config.rs b/rust/src/virtio/config.rs
index ab780f6..8ff473b 100644
--- a/rust/src/virtio/config.rs
+++ b/rust/src/virtio/config.rs
@@ -8,7 +8,6 @@ use super::eventfd::IoEventFd;
 use super::vring::Vring;
 use super::virtqueue::InterruptLine;
 use super::bus::VirtioDeviceConfig;
-use super::consts::DEFAULT_QUEUE_SIZE;
 
 ///
 /// Manages a set of virtqueues during device intitialization.
@@ -28,7 +27,7 @@ impl VirtQueueConfig {
             num_queues: dev_config.num_queues(),
             selected_queue: 0,
             enabled_features: 0,
-            vrings: create_vrings(memory,dev_config.num_queues()),
+            vrings: create_vrings(memory,dev_config.queue_sizes()),
             interrupt: InterruptLine::from_config(&dev_config)?,
             events: create_ioeventfds(&dev_config)?,
         })
@@ -123,10 +122,10 @@ fn create_ioeventfds(conf: &VirtioDeviceConfig) -> Result<Vec<Arc<IoEventFd>>> {
     Ok(v)
 }
 
-fn create_vrings(memory: &GuestRam, n: usize) -> Vec<Vring> {
-    let mut v = Vec::with_capacity(n);
-    for _ in 0..n {
-        v.push(Vring::new(memory.clone(), DEFAULT_QUEUE_SIZE));
+fn create_vrings(memory: &GuestRam, queue_sizes: &[usize]) -> Vec<Vring> {
+    let mut v = Vec::with_capacity(queue_sizes.len());
+    for &sz in queue_sizes {
+        v.push(Vring::new(memory.clone(), sz as u16))
     }
     v
 }