motorhead/qemu
1
0
Fork 0
mirror of https://github.com/Motorhead1991/qemu.git synced 2025-08-06 01:03:55 -06:00
Code Issues Projects Releases Packages Wiki Activity Actions

scsi: only access SCSIDevice->requests from one thread

Browse source 
Stop depending on the AioContext lock and instead access
SCSIDevice->requests from only one thread at a time:
- When the VM is running only the BlockBackend's AioContext may access
  the requests list.
- When the VM is stopped only the main loop may access the requests
  list.

These constraints protect the requests list without the need for locking
in the I/O code path.

Note that multiple IOThreads are not supported yet because the code
assumes all SCSIRequests are executed from a single AioContext. Leave
that as future work.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-ID: <20231204164259.1515217-2-stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2023-12-04 11:42:56 -05:00 • committed by Kevin Wolf
parent bb6e2511eb
commit eaad0fe260
2 changed files with 131 additions and 57 deletions
Download patch file Download diff file Expand all files Collapse all files

7
include/hw/scsi/scsi.h
View file

@ -69,14 +69,19 @@ struct SCSIDevice
{
DeviceState qdev;
VMChangeStateEntry *vmsentry;
QEMUBH *bh;
uint32_t id;
BlockConf conf;
SCSISense unit_attention;
bool sense_is_ua;
uint8_t sense[SCSI_SENSE_BUF_SIZE];
uint32_t sense_len;
/*
* The requests list is only accessed from the AioContext that executes
* requests or from the main loop when IOThread processing is stopped.
*/
QTAILQ_HEAD(, SCSIRequest) requests;
uint32_t channel;
uint32_t lun;
int blocksize;