Re: [Qemu-devel] [PATCH][RESEND] qemu:e1000: Fix RX descriptor low threshold interrupt logic

[Anthony Liguori <aliguori@us.ibm.com>]

Alex Williamson wrote:
> The RXDMT0 interrupt is supposed to fire when the number of free
> RX descriptors drops to some fraction of the total descriptors.
> However in practice, it seems like we're adding this interrupt
> cause on every RX.  Fix the logic to treat (tail - head) as the
> number of free entries rather than the number of used entries.
>
> Signed-off-by: Alex Williamson <alex.williamson@hp.com>
>   

Applied to trunk and stable, thanks.

Regards,

Anthony Liguori

> ---
>
>  hw/e1000.c |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/hw/e1000.c b/hw/e1000.c
> index e6155d6..1644201 100644
> --- a/hw/e1000.c
> +++ b/hw/e1000.c
> @@ -666,8 +666,8 @@ e1000_receive(void *opaque, const uint8_t *buf, int size)
>      n = E1000_ICS_RXT0;
>      if ((rdt = s->mac_reg[RDT]) < s->mac_reg[RDH])
>          rdt += s->mac_reg[RDLEN] / sizeof(desc);
> -    if (((rdt - s->mac_reg[RDH]) * sizeof(desc)) << s->rxbuf_min_shift >=
> -        s->mac_reg[RDLEN])
> +    if (((rdt - s->mac_reg[RDH]) * sizeof(desc)) <= s->mac_reg[RDLEN] >>
> +        s->rxbuf_min_shift)
>          n |= E1000_ICS_RXDMT0;
>  
>      set_ics(s, 0, n);
>
>
>
>
>