Guenter Roeck ea84a44250 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 <linux@roeck-us.net>		2019-01-11 13:57:24 +01:00
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emulation.h	scsi-generic: avoid invalid access to struct when emulating block limits	2018-11-06 21:35:06 +01:00
esp.h	scsi: esp: Defer command completion until previous interrupts have been handled	2019-01-11 13:57:24 +01:00
scsi.h	scsi-generic: avoid invalid access to struct when emulating block limits	2018-11-06 21:35:06 +01:00