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[Qemu-devel] [PATCH v3 16/17] ahci: Recompute cur_cmd on migrate post lo

From: John Snow
Subject: [Qemu-devel] [PATCH v3 16/17] ahci: Recompute cur_cmd on migrate post load
Date: Tue, 10 Feb 2015 13:19:28 -0500

When the AHCI HBA device is migrated, all of the information that
led to the request being created is stored in the AHCIDevice
structures, except for pointers into guest data where return
information needs to be stored.

The "cur_cmd" field is usually responsible for this.

To rebuild the cur_cmd pointer post-migration, we can utilize
the busy_slot index to figure out where the command header
we are still processing is.

This allows a machine in a halted state from rerror=stop or
werror=stop to be migrated and resume operations without issue.

Signed-off-by: John Snow <address@hidden>
 hw/ide/ahci.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/hw/ide/ahci.c b/hw/ide/ahci.c
index 56a4867..5a1973f 100644
--- a/hw/ide/ahci.c
+++ b/hw/ide/ahci.c
@@ -1376,6 +1376,11 @@ static int ahci_state_post_load(void *opaque, int 
         if (ad->busy_slot == -1) {
             check_cmd(s, i);
+        } else {
+            /* We are in the middle of a command, and may need to access
+             * the command header in guest memory again. */
+            assert(ad->busy_slot >= 0 && ad->busy_slot < AHCI_MAX_CMDS);
+            ad->cur_cmd = &((AHCICmdHdr *)ad->lst)[ad->busy_slot];

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