From ea84a44250f79566484692bb000e97776ac66047 Mon Sep 17 00:00:00 2001 From: Guenter Roeck Date: Thu, 29 Nov 2018 09:17:42 -0800 Subject: scsi: esp: Defer command completion until previous interrupts have been handled The guest OS reads RSTAT, RSEQ, and RINTR, and expects those registers to reflect a consistent state. However, it is possible that the registers can change after RSTAT was read, but before RINTR is read, when esp_command_complete() is called. Guest OS qemu -------- ---- [handle interrupt] Read RSTAT esp_command_complete() RSTAT = STAT_ST esp_dma_done() RSTAT |= STAT_TC RSEQ = 0 RINTR = INTR_BS Read RSEQ Read RINTR RINTR = 0 RSTAT &= ~STAT_TC RSEQ = SEQ_CD The guest OS would then try to handle INTR_BS combined with an old value of RSTAT. This sometimes resulted in lost events, spurious interrupts, guest OS confusion, and stalled SCSI operations. A typical guest error log (observed with various versions of Linux) looks as follows. scsi host1: Spurious irq, sreg=13. ... scsi host1: Aborting command [84531f10:2a] scsi host1: Current command [f882eea8:35] scsi host1: Queued command [84531f10:2a] scsi host1: Active command [f882eea8:35] scsi host1: Dumping command log scsi host1: ent[15] CMD val[44] sreg[90] seqreg[00] sreg2[00] ireg[20] ss[00] event[0c] scsi host1: ent[16] CMD val[01] sreg[90] seqreg[00] sreg2[00] ireg[20] ss[02] event[0c] scsi host1: ent[17] CMD val[43] sreg[90] seqreg[00] sreg2[00] ireg[20] ss[02] event[0c] scsi host1: ent[18] EVENT val[0d] sreg[92] seqreg[04] sreg2[00] ireg[18] ss[00] event[0c] ... Defer handling command completion until previous interrupts have been handled to fix the problem. Signed-off-by: Guenter Roeck --- include/hw/scsi/esp.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/hw/scsi/esp.h') diff --git a/include/hw/scsi/esp.h b/include/hw/scsi/esp.h index 682a0d2..adab63d 100644 --- a/include/hw/scsi/esp.h +++ b/include/hw/scsi/esp.h @@ -23,6 +23,8 @@ struct ESPState { int32_t ti_size; uint32_t ti_rptr, ti_wptr; uint32_t status; + uint32_t deferred_status; + bool deferred_complete; uint32_t dma; uint8_t ti_buf[TI_BUFSZ]; SCSIBus bus; -- cgit v1.1