From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55898) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VjnLG-0007GT-CY for qemu-devel@nongnu.org; Fri, 22 Nov 2013 04:48:08 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VjnLA-00037f-E4 for qemu-devel@nongnu.org; Fri, 22 Nov 2013 04:48:02 -0500 Received: from mx1.redhat.com ([209.132.183.28]:39021) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VjnLA-00037Z-64 for qemu-devel@nongnu.org; Fri, 22 Nov 2013 04:47:56 -0500 Received: from int-mx01.intmail.prod.int.phx2.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id rAM9lskO002362 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Fri, 22 Nov 2013 04:47:55 -0500 Message-ID: <528F2836.8010800@redhat.com> Date: Fri, 22 Nov 2013 17:47:34 +0800 From: Jason Wang MIME-Version: 1.0 References: <1385064260-20962-1-git-send-email-vyasevic@redhat.com> <1385064260-20962-2-git-send-email-vyasevic@redhat.com> In-Reply-To: <1385064260-20962-2-git-send-email-vyasevic@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [RFC PATCH 1/2] e1000: Use Address_Available bit as HW latch List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Vlad Yasevich , qemu-devel@nongnu.org Cc: alex.williamson@redhat.com, akong@redhat.com, stefanha@redhat.com, mst@redhat.com On 11/22/2013 04:04 AM, Vlad Yasevich wrote: > e1000 provides a E1000_RAH_AV bit on every complete write > to the Receive Address Register. We can use this bit > 2 ways: > 1) To trigger HMP notifications. When the bit is set the > mac address is fully set and we can update the HMP. > > 2) We can turn off he bit on the write to low order bits of > the Receive Address Register, so that we would not try > to match received traffic to this address when it is > not completely set. > > Signed-off-by: Vlad Yasevich > --- > hw/net/e1000.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/hw/net/e1000.c b/hw/net/e1000.c > index ae63591..82978ea 100644 > --- a/hw/net/e1000.c > +++ b/hw/net/e1000.c > @@ -1106,10 +1106,19 @@ mac_writereg(E1000State *s, int index, uint32_t val) > > s->mac_reg[index] = val; > > - if (index == RA || index == RA + 1) { > + switch (index) { > + case RA: > + /* Mask off AV bit on the write of the low dword. The write of > + * the high dword will set the bit. This way a half-written > + * mac address will not be used to filter on rx. > + */ > + s->mac_reg[RA+1] &= ~E1000_RAH_AV; If a stupid driver write high dword first, it won't receive any packets. > + break; > + case (RA + 1): > macaddr[0] = cpu_to_le32(s->mac_reg[RA]); > macaddr[1] = cpu_to_le32(s->mac_reg[RA + 1]); > qemu_format_nic_info_str(qemu_get_queue(s->nic), (uint8_t *)macaddr); Guest may invalid the mac address by clearing the AV bit through writing to high dword. So this may notify a wrong mac address. Generally, we could teset the AV bit before notification, and try to do the this on both high and low dword. This obeys specs and receive_filter() above. If we don't want half-written status, driver should clear AV bit before each writing of new mac address. But looks like linux and freebsd does not do this. But the window is really small and harmless. > + break; > } > } >