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

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

[Alex Williamson]

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>
---

 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);

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

[Anthony Liguori]

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);
>
>
>
>
>