From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37379) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Y1TDp-0003Fe-8N for qemu-devel@nongnu.org; Thu, 18 Dec 2014 00:02:01 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Y1TDk-0007pe-Hy for qemu-devel@nongnu.org; Thu, 18 Dec 2014 00:01:57 -0500 Received: from mx4-phx2.redhat.com ([209.132.183.25]:44194) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Y1TDk-0007pX-A8 for qemu-devel@nongnu.org; Thu, 18 Dec 2014 00:01:52 -0500 Date: Thu, 18 Dec 2014 00:01:48 -0500 (EST) From: Jason Wang Message-ID: <1334031842.234534.1418878908279.JavaMail.zimbra@redhat.com> In-Reply-To: <1418275427-18921-3-git-send-email-rich.tollerton@ni.com> References: <1418275427-18921-1-git-send-email-rich.tollerton@ni.com> <1418275427-18921-3-git-send-email-rich.tollerton@ni.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v2 2/2] e1000: decrement RDT if equal to RDH List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Richard Tollerton Cc: mst@redhat.com, qemu-devel@nongnu.org, Jeff Westfahl , kraxel@redhat.com ----- Original Message ----- > Some drivers set RDT=RDH. Oddly, this works on real hardware. To work > around this, autodecrement RDT when this happens. > > Signed-off-by: Richard Tollerton > Signed-off-by: Jeff Westfahl > --- > hw/net/e1000.c | 6 ++++++ > 1 file changed, 6 insertions(+) Please describe more details on the issue. The spec 3.2.6 said: " When the head pointer is equal to the tail pointer, the ring is empty. " So RDT=RDH in fact empty the ring. No? > > diff --git a/hw/net/e1000.c b/hw/net/e1000.c > index 44ae3a8..b8cbfc1 100644 > --- a/hw/net/e1000.c > +++ b/hw/net/e1000.c > @@ -1152,6 +1152,12 @@ mac_writereg(E1000State *s, int index, uint32_t val) > static void > set_rdt(E1000State *s, int index, uint32_t val) > { > + if (val == s->mac_reg[RDH]) { /* Decrement RDT if it's too big */ > + if (val == 0) { > + val = s->mac_reg[RDLEN] / sizeof(struct e1000_rx_desc); > + } > + val--; > + } > s->mac_reg[index] = val & 0xffff; > if (e1000_has_rxbufs(s, 1)) { > qemu_flush_queued_packets(qemu_get_queue(s->nic)); > -- > 2.1.3 > > >