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virtio-devices: console: Fix descriptor chain processing

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Both process_input_queue and process_output_queue were only processing
the first descriptor of a chain, leading to data loss if the driver used
chained descriptors.

This change iterates through all descriptors in a chain. It also moves
the flush call out of the descriptor loops to improve performance.

Signed-off-by: Andrei Vagin <avagin@google.com>
This commit is contained in:
Andrei Vagin
2026-03-07 01:25:04 +00:00
committed by Wei Liu
parent 49156c720c
commit 2698cfed98
1 changed files with 39 additions and 28 deletions
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67
virtio-devices/src/console.rs
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@@ -51,8 +51,6 @@ const VIRTIO_CONSOLE_F_SIZE: u64 = 0;
#[derive(Error, Debug)]
enum Error {
#[error("Descriptor chain too short")]
DescriptorChainTooShort,
#[error("Failed to read from guest memory")]
GuestMemoryRead(#[source] vm_memory::guest_memory::Error),
#[error("Failed to write to guest memory")]
@@ -210,21 +208,28 @@ impl ConsoleEpollHandler {
}
while let Some(mut desc_chain) = recv_queue.pop_descriptor_chain(self.mem.memory()) {
let desc = desc_chain.next().ok_or(Error::DescriptorChainTooShort)?;
let len = cmp::min(desc.len(), in_buffer.len() as u32);
let source_slice = in_buffer.drain(..len as usize).collect::<Vec<u8>>();
let mut total_len = 0;
while let Some(desc) = desc_chain.next() {
if in_buffer.is_empty() {
break;
}
let len = cmp::min(desc.len(), in_buffer.len() as u32);
let source_slice = in_buffer.drain(..len as usize).collect::<Vec<u8>>();
desc_chain
.memory()
.write_slice(
&source_slice[..],
desc.addr()
.translate_gva(self.access_platform.as_deref(), desc.len() as usize),
)
.map_err(Error::GuestMemoryWrite)?;
desc_chain
.memory()
.write_slice(
&source_slice[..],
desc.addr()
.translate_gva(self.access_platform.as_deref(), desc.len() as usize),
)
.map_err(Error::GuestMemoryWrite)?;
total_len += len;
}
recv_queue
.add_used(desc_chain.memory(), desc_chain.head_index(), len)
.add_used(desc_chain.memory(), desc_chain.head_index(), total_len)
.map_err(Error::QueueAddUsed)?;
used_descs = true;
@@ -248,21 +253,23 @@ impl ConsoleEpollHandler {
let mut used_descs = false;
while let Some(mut desc_chain) = trans_queue.pop_descriptor_chain(self.mem.memory()) {
let desc = desc_chain.next().ok_or(Error::DescriptorChainTooShort)?;
if let Some(out) = &mut self.out {
let mut buf: Vec<u8> = Vec::new();
desc_chain
.memory()
.write_volatile_to(
desc.addr()
.translate_gva(self.access_platform.as_deref(), desc.len() as usize),
&mut buf,
desc.len() as usize,
)
.map_err(Error::GuestMemoryRead)?;
while let Some(desc) = desc_chain.next() {
if let Some(out) = &mut self.out {
let mut buf: Vec<u8> = Vec::new();
desc_chain
.memory()
.write_volatile_to(
desc.addr().translate_gva(
self.access_platform.as_deref(),
desc.len() as usize,
),
&mut buf,
desc.len() as usize,
)
.map_err(Error::GuestMemoryRead)?;
out.write_all(&buf).map_err(Error::OutputWriteAll)?;
out.flush().map_err(Error::OutputFlush)?;
out.write_all(&buf).map_err(Error::OutputWriteAll)?;
}
}
trans_queue
.add_used(desc_chain.memory(), desc_chain.head_index(), 0)
@@ -270,6 +277,10 @@ impl ConsoleEpollHandler {
used_descs = true;
}
if used_descs && let Some(out) = &mut self.out {
out.flush().map_err(Error::OutputFlush)?;
}
Ok(used_descs)
}