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ahci: fix win7 hang on boot 

When AHCI executes an asynchronous IDE command, it checked DRDY without
checking either DRQ or BSY.  This sometimes caused interrupt to be sent
before command is actually completed.

This resulted in a race condition: if guest then managed to access the
device before command has completed, it would hang waiting for an
interrupt.
This was observed with windows 7 guests.

To fix, check for DRQ or BSY in additiona to DRDY, if set,
the command is asynchronous so delay the interrupt until
asynchronous done callback is invoked.

Reported-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Alexander Graf 2013-10-28 21:01:51 +02:00 committed by Kevin Wolf
parent 1841f8801c
commit 8464b273d6
1 changed files with 2 additions and 1 deletions
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3
hw/ide/ahci.c
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@ -961,7 +961,8 @@ static int handle_cmd(AHCIState *s, int port, int slot)
/* We're ready to process the command in FIS byte 2. */
ide_exec_cmd(&s->dev[port].port, cmd_fis[2]);
if (s->dev[port].port.ifs[0].status & READY_STAT) {
if ((s->dev[port].port.ifs[0].status & (READY_STAT|DRQ_STAT|BUSY_STAT)) ==
READY_STAT) {
ahci_write_fis_d2h(&s->dev[port], cmd_fis);
}
}