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


From: Markus Armbruster
Subject: Re: [Qemu-devel] [PATCH v3 4/4] ivshmem: Disable irqfd on device reset
Date: Fri, 08 Dec 2017 14:36:34 +0100
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/25.3 (gnu/linux)

Ladi Prosek <address@hidden> 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 <address@hidden>
> ---
>  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.



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