Re: [Qemu-devel] [PATCH for-2.10 2/2] xilinx-spips: add a migration blocker when using mmio_execution

["Edgar E. Iglesias" <edgar.iglesias@gmail.com>]

On Tue, Aug 01, 2017 at 11:13:56AM +0200, KONRAD Frederic wrote:
> 
> 
> On 08/01/2017 11:00 AM, Peter Maydell wrote:
> >On 1 August 2017 at 09:10, KONRAD Frederic <frederic.konrad@adacore.com> wrote:
> >>This adds a migration blocker when mmio_execution has been used.
> >>
> >>Signed-off-by: KONRAD Frederic <frederic.konrad@adacore.com>
> >>---
> >>  hw/ssi/xilinx_spips.c | 11 +++++++++++
> >>  1 file changed, 11 insertions(+)
> >>
> >>diff --git a/hw/ssi/xilinx_spips.c b/hw/ssi/xilinx_spips.c
> >>index e833028..d46491f 100644
> >>--- a/hw/ssi/xilinx_spips.c
> >>+++ b/hw/ssi/xilinx_spips.c
> >>@@ -31,6 +31,8 @@
> >>  #include "hw/ssi/ssi.h"
> >>  #include "qemu/bitops.h"
> >>  #include "hw/ssi/xilinx_spips.h"
> >>+#include "qapi/error.h"
> >>+#include "migration/blocker.h"
> >>
> >>  #ifndef XILINX_SPIPS_ERR_DEBUG
> >>  #define XILINX_SPIPS_ERR_DEBUG 0
> >>@@ -139,6 +141,7 @@ typedef struct {
> >>
> >>      uint8_t lqspi_buf[LQSPI_CACHE_SIZE];
> >>      hwaddr lqspi_cached_addr;
> >>+    Error *migration_blocker;
> >>  } XilinxQSPIPS;
> >>
> >>  typedef struct XilinxSPIPSClass {
> >>@@ -603,6 +606,14 @@ static void *lqspi_request_mmio_ptr(void *opaque, hwaddr addr, unsigned *size,
> >>      XilinxQSPIPS *q = opaque;
> >>      hwaddr offset_within_the_region = addr & ~(LQSPI_CACHE_SIZE - 1);
> >>
> >>+    /* mmio_execution breaks migration better aborting than having strange
> >>+     * bugs.
> >>+     */
> >>+    if (!q->migration_blocker) {
> >>+        error_setg(&q->migration_blocker, "booting from SPI breaks migration");
> >>+        migrate_add_blocker(q->migration_blocker, &error_fatal);
> >>+    }
> >>+
> >
> >This doesn't handle the case when migration is already in progress
> >and this function is called (which will cause migrate_add_blocker
> >to fail).
> 
> Maybe I can make the request_ptr to fail if migration is in
> progress.. But is that safe or do I risk a race.
>

Hi Fred,

At this stage, perhaps we should just register the blocker when this dev realizes.

If a request_ptr comes in during migration, the VM will fail either way...

Cheers,
Edgar