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block: Allow (and ignore) FLUSH requests on read-only devices

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OVMF sends FLUSH requests to read-only virtio-block devices.  Refusing
these requests prevents OVMF from accessing the EFI System Partition and
therefore makes VMs unable to boot.  Accept these requests instead.
them.

Ignoring these requests is possible, but inconsistent with fsync(2)
which honors them.

Fixes: #7698
Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com>
This commit is contained in:
Demi Marie Obenour 2026-02-14 02:54:34 -05:00 • committed by Rob Bradford
parent ff4c8f7480
commit 80ea1fe62d
1 changed files with 3 additions and 1 deletions
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4
virtio-devices/src/block.rs
View file

@ -169,7 +169,9 @@ fn has_feature(features: u64, feature_flag: u64) -> bool {
impl BlockEpollHandler {
fn check_request(features: u64, request_type: RequestType) -> result::Result<(), ExecuteError> {
if has_feature(features, VIRTIO_BLK_F_RO.into())
&& !(request_type == RequestType::In || request_type == RequestType::GetDeviceId)
&& !(request_type == RequestType::In
|| request_type == RequestType::GetDeviceId
|| request_type == RequestType::Flush)
{
// For virtio spec compliance
// "A device MUST set the status byte to VIRTIO_BLK_S_IOERR for a write request