[Qemu-devel] [PATCH] ahci fix: windows boots fine. need to review with kwolf

[Qemu-devel] [PATCH] ahci fix: windows boots fine. need to review with kwolf

[Michael S. Tsirkin]

From: Alexander Graf <agraf@suse.de>

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>

---
 hw/ide/ahci.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/hw/ide/ahci.c b/hw/ide/ahci.c
index a8be62c..fbea9e8 100644
--- a/hw/ide/ahci.c
+++ b/hw/ide/ahci.c
@@ -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);
         }
     }
-- 
MST

Re: [Qemu-devel] [PATCH] ahci fix: windows boots fine. need to review with kwolf

[Michael S. Tsirkin]

On Mon, Oct 28, 2013 at 09:00:15PM +0200, Michael S. Tsirkin wrote:
> From: Alexander Graf <agraf@suse.de>
> 
> 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>

Sorry about the subject, forgot to update it.
I reposted with a fixed subject.

> ---
>  hw/ide/ahci.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/ide/ahci.c b/hw/ide/ahci.c
> index a8be62c..fbea9e8 100644
> --- a/hw/ide/ahci.c
> +++ b/hw/ide/ahci.c
> @@ -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);
>          }
>      }
> -- 
> MST