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

[Jason Wang]

Michael S. Tsirkin writes:
 > 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 <address@hidden>
 > >  > >  > >  > 
 > >  > >  > > 
 > >  > >  > > 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.
 > 

Try printing CPUX86State through gdb and the filed used to do the save/restore
are the same. Have done the check for mtrr_var and the value are same for both
src and dst. And looks like it was never used by kvm.

 > 
 > > 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?
 > 

One byte delta for virtio-blk section at offset 377. And also get delta for ide
section ( so I didn't try your patch of stopping bh of ide becuse for virtio-blk
we even do not use ide ).

 > 
 > >  > > 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! */
 > >  > >      }