Re: [Qemu-devel] [PATCH] ivshmem: fix guest unable to start with ioeventfd

[Cam Macdonell]

2011/11/30 Cam Macdonell <address@hidden>:
> 2011/11/30 Zang Hongyong <address@hidden>:
>> Can this bug fix patch be applied yet?
>
> Sorry, for not replying yet.  I'll test your patch within the next day.

Have you confirmed the proper receipt of interrupts in the receiving guests?

I can confirm the bug occurs with ioeventfd enabled and that the
patches fixes it, but sometime after 15.1, I no longer see interrupts
(MSI or regular) being delivered in the guest.

I will bisect tomorrow.

Cam

>
>> With this bug, guest os cannot successfully boot with ioeventfd.
>> Thus the new PIO DoorBell patch cannot be posted.
>
> Well, you can certainly post the new patch, just clarify that it's
> dependent on this patch.
>
> Sincerely,
> Cam
>
>>
>> Thanks,
>> Hongyong
>>
>> 于 2011/11/24,星期四 18:05, address@hidden 写道:
>>> From: Hongyong Zang <address@hidden>
>>>
>>> When a guest boots with ioeventfd, an error (by gdb) occurs:
>>>   Program received signal SIGSEGV, Segmentation fault.
>>>   0x00000000006009cc in setup_ioeventfds (s=0x171dc40)
>>>       at /home/louzhengwei/git_source/qemu-kvm/hw/ivshmem.c:363
>>>   363             for (j = 0; j < s->peers[i].nb_eventfds; j++) {
>>> The bug is due to accessing s->peers which is NULL.
>>>
>>> This patch uses the memory region API to replace the old one 
>>> kvm_set_ioeventfd_mmio_long().
>>> And this patch makes memory_region_add_eventfd() called in ivshmem_read() 
>>> when qemu receives
>>> eventfd information from ivshmem_server.
>>>
>>> Signed-off-by: Hongyong Zang <address@hidden>
>>> ---
>>>  hw/ivshmem.c |   41 ++++++++++++++---------------------------
>>>  1 files changed, 14 insertions(+), 27 deletions(-)
>>>
>>> diff --git a/hw/ivshmem.c b/hw/ivshmem.c
>>> index 242fbea..be26f03 100644
>>> --- a/hw/ivshmem.c
>>> +++ b/hw/ivshmem.c
>>> @@ -58,7 +58,6 @@ typedef struct IVShmemState {
>>>      CharDriverState *server_chr;
>>>      MemoryRegion ivshmem_mmio;
>>>
>>> -    pcibus_t mmio_addr;
>>>      /* We might need to register the BAR before we actually have the 
>>> memory.
>>>       * So prepare a container MemoryRegion for the BAR immediately and
>>>       * add a subregion when we have the memory.
>>> @@ -346,8 +345,14 @@ static void close_guest_eventfds(IVShmemState *s, int 
>>> posn)
>>>      guest_curr_max = s->peers[posn].nb_eventfds;
>>>
>>>      for (i = 0; i < guest_curr_max; i++) {
>>> -        kvm_set_ioeventfd_mmio_long(s->peers[posn].eventfds[i],
>>> -                    s->mmio_addr + DOORBELL, (posn << 16) | i, 0);
>>> +        if (ivshmem_has_feature(s, IVSHMEM_IOEVENTFD)) {
>>> +            memory_region_del_eventfd(&s->ivshmem_mmio,
>>> +                                     DOORBELL,
>>> +                                     4,
>>> +                                     true,
>>> +                                     (posn << 16) | i,
>>> +                                     s->peers[posn].eventfds[i]);
>>> +        }
>>>          close(s->peers[posn].eventfds[i]);
>>>      }
>>>
>>> @@ -355,22 +360,6 @@ static void close_guest_eventfds(IVShmemState *s, int 
>>> posn)
>>>      s->peers[posn].nb_eventfds = 0;
>>>  }
>>>
>>> -static void setup_ioeventfds(IVShmemState *s) {
>>> -
>>> -    int i, j;
>>> -
>>> -    for (i = 0; i <= s->max_peer; i++) {
>>> -        for (j = 0; j < s->peers[i].nb_eventfds; j++) {
>>> -            memory_region_add_eventfd(&s->ivshmem_mmio,
>>> -                                      DOORBELL,
>>> -                                      4,
>>> -                                      true,
>>> -                                      (i << 16) | j,
>>> -                                      s->peers[i].eventfds[j]);
>>> -        }
>>> -    }
>>> -}
>>> -
>>>  /* this function increase the dynamic storage need to store data about 
>>> other
>>>   * guests */
>>>  static void increase_dynamic_storage(IVShmemState *s, int new_min_size) {
>>> @@ -491,10 +480,12 @@ static void ivshmem_read(void *opaque, const uint8_t 
>>> * buf, int flags)
>>>      }
>>>
>>>      if (ivshmem_has_feature(s, IVSHMEM_IOEVENTFD)) {
>>> -        if (kvm_set_ioeventfd_mmio_long(incoming_fd, s->mmio_addr + 
>>> DOORBELL,
>>> -                        (incoming_posn << 16) | guest_max_eventfd, 1) < 0) 
>>> {
>>> -            fprintf(stderr, "ivshmem: ioeventfd not available\n");
>>> -        }
>>> +        memory_region_add_eventfd(&s->ivshmem_mmio,
>>> +                                  DOORBELL,
>>> +                                  4,
>>> +                                  true,
>>> +                                  (incoming_posn << 16) | 
>>> guest_max_eventfd,
>>> +                                  incoming_fd);
>>>      }
>>>
>>>      return;
>>> @@ -659,10 +650,6 @@ static int pci_ivshmem_init(PCIDevice *dev)
>>>      memory_region_init_io(&s->ivshmem_mmio, &ivshmem_mmio_ops, s,
>>>                            "ivshmem-mmio", IVSHMEM_REG_BAR_SIZE);
>>>
>>> -    if (ivshmem_has_feature(s, IVSHMEM_IOEVENTFD)) {
>>> -        setup_ioeventfds(s);
>>> -    }
>>> -
>>>      /* region for registers*/
>>>      pci_register_bar(&s->dev, 0, PCI_BASE_ADDRESS_SPACE_MEMORY,
>>>                       &s->ivshmem_mmio);
>>
>>