Re: [Qemu-devel] [PATCHv3 4/6] virtio-net: stop/start bh when appropriate

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Dec 02, 2010 at 10:19:55PM +0800, Jason Wang wrote:
> Michael S. Tsirkin writes:
>  > On Thu, Dec 02, 2010 at 08:56:30PM +0800, Jason Wang wrote:
>  > > Michael S. Tsirkin writes:
>  > >  > On Wed, Dec 01, 2010 at 01:45:09PM +0800, Jason Wang wrote:
>  > >  > > Michael S. Tsirkin writes:
>  > >  > >  > Avoid sending out packets, and modifying
>  > >  > >  > device state, when VM is stopped.
>  > >  > >  > Add assert statements to verify this does not happen.
>  > >  > >  > 
>  > >  > >  > Avoid scheduling bh when vhost-net is started.
>  > >  > >  > 
>  > >  > >  > Stop bh when driver disabled bus mastering
>  > >  > >  > (we must not access memory after this).
>  > >  > >  > 
>  > >  > >  > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
>  > >  > >  > 
>  > >  > > 
>  > >  > > There's no need to disable it bh we call qemu_aio_flush() after
>  > >  > > vm_state_notify() in do_vm_stop(). And for timer, looks like every device should
>  > >  > > stop its timer in vm state change handler, not only for virtio-net?
>  > >  > 
>  > >  > BTW I fixed some typos. Here a fixed version.
>  > >  > Jason, could you review/test please?
>  > >  > 
>  > > 
>  > > Have done the test, it's more stable than before but still get small deltas in
>  > > cpu section.
>  > 
>  > And just to clarify: no more deltas in the memory section?
>  > 
> 
> Yes.
> 
> And the offset for cpu section is 1161-1165

As far as I can say the state is in
target-i386/machine.c
static const VMStateDescription vmstate_cpu.
Need to do some math to find this:

I think this is mtrr_var, but maybe my math is off.
I would sugest printing out the state and see
what is changed exactly.


> and sometimes I get deltas for ide
> section at offset 295 and 314.

I see that ide has some bh processing.  Most likely that starts io after
vmstop?  I suggest adding a vm state handler and checking vm status in
ide_dma_restart_bh.

Start with an assert, just for debug.

Also, what if we use virtio-blk?


>  > > I didn't find any interesting difference by checking the
>  > > CPUX86State in the dest in kvm_arch_load_regs(), any thought on this?
>  > > 
>  > > BTW, looks like the error_code was missed in saving the cpu state:
>  > > 
>  > > diff --git a/target-i386/cpu.h b/target-i386/cpu.h
>  > > index 35a1a51..145bb38 100644
>  > > --- a/target-i386/cpu.h
>  > > +++ b/target-i386/cpu.h
>  > > @@ -687,7 +687,7 @@ typedef struct CPUX86State {
>  > >      uint64_t pat;
>  > >  
>  > >      /* exception/interrupt handling */
>  > > -    int error_code;
>  > > +    uint32_t error_code;
>  > >      int exception_is_int;
>  > >      target_ulong exception_next_eip;
>  > >      target_ulong dr[8]; /* debug registers */
>  > > @@ -935,7 +935,7 @@ CPUState *pc_new_cpu(const char *cpu_model);
>  > >  #define cpu_list_id x86_cpu_list
>  > >  #define cpudef_setup	x86_cpudef_setup
>  > >  
>  > > -#define CPU_SAVE_VERSION 12
>  > > +#define CPU_SAVE_VERSION 13
>  > >  
>  > >  /* MMU modes definitions */
>  > >  #define MMU_MODE0_SUFFIX _kernel
>  > > diff --git a/target-i386/machine.c b/target-i386/machine.c
>  > > index 4398801..fa231d8 100644
>  > > --- a/target-i386/machine.c
>  > > +++ b/target-i386/machine.c
>  > > @@ -474,6 +474,8 @@ static const VMStateDescription vmstate_cpu = {
>  > >          VMSTATE_UINT64_V(xcr0, CPUState, 12),
>  > >          VMSTATE_UINT64_V(xstate_bv, CPUState, 12),
>  > >          VMSTATE_YMMH_REGS_VARS(ymmh_regs, CPUState, CPU_NB_REGS, 12),
>  > > +
>  > > +        VMSTATE_UINT32_V(error_code, CPUState, 13),
>  > >          VMSTATE_END_OF_LIST()
>  > >          /* The above list is not sorted /wrt version numbers, watch out! */
>  > >      }