Re: [Qemu-devel] [PATCH v3 4/4] ivshmem: Disable irqfd on device reset

[Ladi Prosek <lprosek@redhat.com>]

On Fri, Dec 8, 2017 at 2:36 PM, Markus Armbruster <armbru@redhat.com> wrote:
> Ladi Prosek <lprosek@redhat.com> writes:
>
>> The effects of ivshmem_enable_irqfd() was not undone on device reset.
>>
>> This manifested as:
>> ivshmem_add_kvm_msi_virq: Assertion `!s->msi_vectors[vector].pdev' failed.
>>
>> when irqfd was enabled before reset and then enabled again after reset, making
>> ivshmem_enable_irqfd() run for the second time.
>>
>> To reproduce, run:
>>
>>   ivshmem-server
>>
>> and QEMU with:
>>
>>   -device ivshmem-doorbell,chardev=iv
>>   -chardev socket,path=/tmp/ivshmem_socket,id=iv
>>
>> then install the Windows driver, at the time of writing available at:
>>
>> https://github.com/virtio-win/kvm-guest-drivers-windows/tree/master/ivshmem
>>
>> and crash-reboot the guest by inducing a BSOD.
>>
>> Signed-off-by: Ladi Prosek <lprosek@redhat.com>
>> ---
>>  hw/misc/ivshmem.c | 24 +++++++++++++-----------
>>  1 file changed, 13 insertions(+), 11 deletions(-)
>>
>> diff --git a/hw/misc/ivshmem.c b/hw/misc/ivshmem.c
>> index d1bb246d12..4be0d2627b 100644
>> --- a/hw/misc/ivshmem.c
>> +++ b/hw/misc/ivshmem.c
>> @@ -758,17 +758,6 @@ static void ivshmem_msix_vector_use(IVShmemState *s)
>>      }
>>  }
>>
>> -static void ivshmem_reset(DeviceState *d)
>> -{
>> -    IVShmemState *s = IVSHMEM_COMMON(d);
>> -
>> -    s->intrstatus = 0;
>> -    s->intrmask = 0;
>> -    if (ivshmem_has_feature(s, IVSHMEM_MSI)) {
>> -        ivshmem_msix_vector_use(s);
>> -    }
>> -}
>> -
>>  static int ivshmem_setup_interrupts(IVShmemState *s, Error **errp)
>>  {
>>      /* allocate QEMU callback data for receiving interrupts */
>> @@ -855,6 +844,19 @@ static void ivshmem_disable_irqfd(IVShmemState *s)
>>
>>  }
>>
>> +static void ivshmem_reset(DeviceState *d)
>> +{
>> +    IVShmemState *s = IVSHMEM_COMMON(d);
>> +
>> +    ivshmem_disable_irqfd(s);
>> +
>> +    s->intrstatus = 0;
>> +    s->intrmask = 0;
>> +    if (ivshmem_has_feature(s, IVSHMEM_MSI)) {
>> +        ivshmem_msix_vector_use(s);
>> +    }
>> +}
>> +
>>  static void ivshmem_write_config(PCIDevice *pdev, uint32_t address,
>>                                   uint32_t val, int len)
>>  {
>
> Why are you moving ivshmem_reset()?  Makes the actual change harder to
> see than necessary.

ivshmem_disable_irqfd() is declared after ivshmem_reset() in the
source file. I generally prefer to order static functions
topologically if possible. If you'd prefer adding a forward decl
instead (fewer lines touched, easier to bisect?) I can certainly do
that. Thanks!