Re: [Qemu-devel] [PATCH/RFC] exec: add cpu_synchronize_state to cpu_memory_rw_debug

[Alex Bennée]

Christian Borntraeger <address@hidden> writes:

> I sometimes got "Cannot access memory" when using the x command
> on the monitor. Turns out that the cpu env did contain stale data
> (e.g. wrong control register content for page table origin).
> We must synchronize the state of the CPU before walking the page
> tables. A similar issues happens for a remote gdb, so lets
> do the cpu_synchronize_state in cpu_memory_rw_debug.
>
> Signed-off-by: Christian Borntraeger <address@hidden>
> ---
>  exec.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/exec.c b/exec.c
> index aabb035..e754a03 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -43,6 +43,7 @@
>  #include "exec/ioport.h"
>  #include "sysemu/dma.h"
>  #include "sysemu/numa.h"
> +#include "sysemu/hw_accel.h"
>  #include "exec/address-spaces.h"
>  #include "sysemu/xen-mapcache.h"
>  #include "trace-root.h"
> @@ -3309,6 +3310,7 @@ int cpu_memory_rw_debug(CPUState *cpu, target_ulong 
> addr,
>      hwaddr phys_addr;
>      target_ulong page;
>
> +    cpu_synchronize_state(cpu);
>      while (len > 0) {
>          int asidx;
>          MemTxAttrs attrs;

This seems like the wrong place to put it. Would we end up doing a
potentially expensive sync operations for every byte/word we dump out?

Certainly when I was messing around with ARM KVM debug I did the
synchronise state as we entered the debug handling (e.g.
gdb_handle_packet/memory_dump)?

--
Alex Bennée