Re: handle_pio looping during domain shutdown, with qemu 4.2.0 in stubdom

['Marek Marczykowski-Górecki' <marmarek@xxxxxxxxxxxxxxxxxxxxxx>]

On Fri, Jun 05, 2020 at 04:48:39PM +0100, Paul Durrant wrote:
> This (untested) patch might help:

It is different now. I don't get domain_crash because of
X86EMUL_UNHANDLEABLE anymore, but I still see handle_pio looping for
some time. But it eventually ends, not really sure why.

I've tried the patch with a modification to make it build:

> diff --git a/xen/arch/x86/hvm/ioreq.c b/xen/arch/x86/hvm/ioreq.c
> index c55c4bc4bc..8aa8779ba2 100644
> --- a/xen/arch/x86/hvm/ioreq.c
> +++ b/xen/arch/x86/hvm/ioreq.c
> @@ -109,12 +109,7 @@ static void hvm_io_assist(struct hvm_ioreq_vcpu *sv, 
> uint64_t data)
>      ioreq_t *ioreq = &v->arch.hvm.hvm_io.io_req;
> 
>      if ( hvm_ioreq_needs_completion(ioreq) )
> -    {
> -        ioreq->state = STATE_IORESP_READY;
>          ioreq->data = data;
> -    }
> -    else
> -        ioreq->state = STATE_IOREQ_NONE;
> 
>      msix_write_completion(v);
>      vcpu_end_shutdown_deferral(v);
> @@ -209,6 +204,9 @@ bool handle_hvm_io_completion(struct vcpu *v)
>          }
>      }
> 
> +    ioreq->state = hvm_ioreq_needs_completion(&vio->ioreq) ?
       vio->io_req->state ... &vio->io_req

> +        STATE_IORESP_READY : STATE_IOREQ_NONE;
> +
>      io_completion = vio->io_completion;
>      vio->io_completion = HVMIO_no_completion;
> 

The full patch (together with my debug prints):
https://gist.github.com/marmarek/da37da3722179057a6e7add4fb361e06

Note some of those X86EMUL_UNHANDLEABLE logged below are about an
intermediate state, not really hvmemul_do_io return value.

And the log:
(XEN) hvm.c:1620:d6v0 All CPUs offline -- powering off.
(XEN) d3v0 handle_pio port 0xb004 read 0x0000 is_shutting_down 0 defer_shutdown 
0 paused_for_shutdown 0 is_shut_down 0
(XEN) emulate.c:263:d3v0 hvmemul_do_io got X86EMUL_UNHANDLEABLE from 
hvm_io_intercept req state 1
(XEN) d3v0 handle_pio port 0xb004 read 0x0000 is_shutting_down 0 defer_shutdown 
0 paused_for_shutdown 0 is_shut_down 0
(XEN) d3v0 handle_pio port 0xb004 write 0x0001 is_shutting_down 0 
defer_shutdown 0 paused_for_shutdown 0 is_shut_down 0
(XEN) emulate.c:263:d3v0 hvmemul_do_io got X86EMUL_UNHANDLEABLE from 
hvm_io_intercept req state 1
(XEN) d3v0 handle_pio port 0xb004 write 0x2001 is_shutting_down 0 
defer_shutdown 0 paused_for_shutdown 0 is_shut_down 0
(XEN) emulate.c:263:d3v0 hvmemul_do_io got X86EMUL_UNHANDLEABLE from 
hvm_io_intercept req state 1
(XEN) d4v0 XEN_DMOP_remote_shutdown domain 3 reason 0
(XEN) d4v0 domain 3 domain_shutdown vcpu_id 0 defer_shutdown 1
(XEN) d4v0 XEN_DMOP_remote_shutdown domain 3 done
(XEN) d4v0 hvm_destroy_ioreq_server called for 3, id 0
(XEN) hvm.c:1620:d5v0 All CPUs offline -- powering off.
(XEN) d1v0 handle_pio port 0xb004 read 0x0000 is_shutting_down 0 defer_shutdown 
0 paused_for_shutdown 0 is_shut_down 0
(XEN) emulate.c:263:d1v0 hvmemul_do_io got X86EMUL_UNHANDLEABLE from 
hvm_io_intercept req state 1
(XEN) d1v0 handle_pio port 0xb004 read 0x0000 is_shutting_down 0 defer_shutdown 
0 paused_for_shutdown 0 is_shut_down 0
(XEN) d1v0 handle_pio port 0xb004 write 0x0001 is_shutting_down 0 
defer_shutdown 0 paused_for_shutdown 0 is_shut_down 0
(XEN) emulate.c:263:d1v0 hvmemul_do_io got X86EMUL_UNHANDLEABLE from 
hvm_io_intercept req state 1
(XEN) d1v0 handle_pio port 0xb004 write 0x2001 is_shutting_down 0 
defer_shutdown 0 paused_for_shutdown 0 is_shut_down 0
(XEN) emulate.c:263:d1v0 hvmemul_do_io got X86EMUL_UNHANDLEABLE from 
hvm_io_intercept req state 1
(XEN) d2v0 XEN_DMOP_remote_shutdown domain 1 reason 0
(XEN) d2v0 domain 1 domain_shutdown vcpu_id 0 defer_shutdown 1
(XEN) d2v0 XEN_DMOP_remote_shutdown domain 1 done
(XEN) grant_table.c:3702:d0v0 Grant release 0x24 ref 0x199 flags 0x2 d5
(XEN) grant_table.c:3702:d0v0 Grant release 0x25 ref 0x19a flags 0x2 d5
(XEN) grant_table.c:3702:d0v0 Grant release 0x3 ref 0x11d flags 0x2 d6
(XEN) grant_table.c:3702:d0v0 Grant release 0x4 ref 0x11e flags 0x2 d6
(XEN) d3v0 handle_pio port 0xb004 read 0x0000 is_shutting_down 1 defer_shutdown 
1 paused_for_shutdown 0 is_shut_down 0
(XEN) emulate.c:263:d3v0 hvmemul_do_io got X86EMUL_UNHANDLEABLE from 
hvm_io_intercept req state 1
(XEN) d3v0 handle_pio port 0xb004 write 0xe3f8 is_shutting_down 1 
defer_shutdown 1 paused_for_shutdown 0 is_shut_down 0
(XEN) emulate.c:263:d3v0 hvmemul_do_io got X86EMUL_UNHANDLEABLE from 
hvm_io_intercept req state 1
(XEN) d3v0 handle_pio port 0xb000 read 0x0000 is_shutting_down 1 defer_shutdown 
1 paused_for_shutdown 0 is_shut_down 0
(XEN) d3v0 handle_pio port 0xb000 read 0x0000 is_shutting_down 1 defer_shutdown 
1 paused_for_shutdown 0 is_shut_down 0

The last one repeats for some time, like 30s or some more (18425 times).
Note the port is different than before. Is it a guest waiting for being
destroyed after requesting so?

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?

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