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[PULL,for-6.2,7/7] hw/ide/ahci: fix broken SError handling

Message ID 20230907034228.4054839-8-jsnow@redhat.com
State New
Headers show
Series [PULL,for-6.2,1/7] hw/ide/core: set ERR_STAT in unsupported command completion | expand

Commit Message

John Snow Sept. 7, 2023, 3:42 a.m. UTC 
From: Niklas Cassel <niklas.cassel@wdc.com>

When encountering an NCQ error, you should not write the NCQ tag to the
SError register. This is completely wrong.

The SError register has a clear definition, where each bit represents a
different error, see PxSERR definition in AHCI 1.3.1.

If we write a random value (like the NCQ tag) in SError, e.g. Linux will
read SError, and will trigger arbitrary error handling depending on the
NCQ tag that happened to be executing.

In case of success, ncq_cb() will call ncq_finish().
In case of error, ncq_cb() will call ncq_err() (which will clear
ncq_tfs->used), and then call ncq_finish(), thus using ncq_tfs->used is
sufficient to tell if finished should get set or not.

Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20230609140844.202795-9-nks@flawful.org
Signed-off-by: John Snow <jsnow@redhat.com>
---
 hw/ide/ahci.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)
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Patch

diff --git a/hw/ide/ahci.c b/hw/ide/ahci.c
index ef6c9fc378..d0a774bc17 100644
--- a/hw/ide/ahci.c
+++ b/hw/ide/ahci.c
@@ -1012,7 +1012,6 @@  static void ncq_err(NCQTransferState *ncq_tfs)
 
     ide_state->error = ABRT_ERR;
     ide_state->status = READY_STAT | ERR_STAT;
-    ncq_tfs->drive->port_regs.scr_err |= (1 << ncq_tfs->tag);
     qemu_sglist_destroy(&ncq_tfs->sglist);
     ncq_tfs->used = 0;
 }
@@ -1022,7 +1021,7 @@  static void ncq_finish(NCQTransferState *ncq_tfs)
     /* If we didn't error out, set our finished bit. Errored commands
      * do not get a bit set for the SDB FIS ACT register, nor do they
      * clear the outstanding bit in scr_act (PxSACT). */
-    if (!(ncq_tfs->drive->port_regs.scr_err & (1 << ncq_tfs->tag))) {
+    if (ncq_tfs->used) {
         ncq_tfs->drive->finished |= (1 << ncq_tfs->tag);
     }