OK for (2). For (1) It would be good to find the exact behaviour of the NE2000 card. Maybe ENISR_RX remain set as long are there are packets in the buffer ? Otherwise your fix is a workaround to correct a bug in the OS driver...
Fabrice. Han, Zhu wrote: > Any comments for this patch? > > Best Regards, > hanzhu > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Han, Zhu > Sent: 2006年5月9日 12:27 > To: qemu-devel@nongnu.org > Subject: [Qemu-devel] patch for ne2000.c > > Hi, All! > > I'm a developer working on xen project! It's well known that xen has > adopted a lot of codes and features from QEMU, especially the Device > Mode Part! > > I fix a bug for ne2000 device emulation code in XEN and I expect it to > be a potential bug for QEMU, either! Because you are all device mode > experts, I submit this patch to you at first in order to ask you to > review my patch. > > Several notes: > 1) Because XEN use event driven mechanism in the main_loop(), irq may be > missed due to the rather high speed and large file! For example, the > ne2000_receive will filled up with the buffer and set up the ENISR_RX > signal, however, the driver could ack and clear the ENISR_RX signal due > to it could only handle a certain amount of packets once in it's > interrupt handling routine! The consequence for this specific steps is > the netcard buffer is full but it never resend the ENISR_RX signal, at > the last, the netcard will be halted! This problem could be rather rare > for QEMU. Anyway, it's a potential bug. > 2) Many of the ne2000 spec said we should set boundary register should > be set to indicate the last receive buffer page the host has read, and > the driver in linux follows this guideline. So, we boundary == index, > the buffer for the netcard is full and we can't write any packets into > this buffer. This minor fix could prevent the ne2000 emulated card from > overflow and destroying the previous received packet page! This problem > could also be rare for QEMU since it could happen only under extreme > circumstance! > > Any feedbacks and comments will be appreciated! > > --- qemu-snapshot-2006-05-07_23\hw\ne2000.c Mon May 08 16:13:49 2006 > +++ ./ne2000.c Mon May 08 16:57:33 2006 > @@ -159,9 +159,19 @@ > } > } > > +static int ne2000_buffer_full(NE2000State *s); > static void ne2000_update_irq(NE2000State *s) > { > int isr; > + > + if(ne2000_buffer_full(s) > + && !(s->isr & ENISR_RX)){ > + /* The freeing space is not enough, tell the ne2k driver > + * to fetch these packets! > + */ > + s->isr |= ENISR_RX; > + } > + > isr = (s->isr & s->imr) & 0x7f; > #if defined(DEBUG_NE2000) > printf("NE2000: Set IRQ line %d to %d (%02x %02x)\n", > @@ -206,7 +216,10 @@ > > index = s->curpag << 8; > boundary = s->boundary << 8; > - if (index < boundary) > + if (index <= boundary) > + /* when index == boundary, we should assume > + * the buffer is full instead of empty! > + */ > avail = boundary - index; > else > avail = (s->stop - s->start) - (index - boundary); > > Best Regards, > hanzhu > > > _______________________________________________ > Qemu-devel mailing list > Qemu-devel@nongnu.org > http://lists.nongnu.org/mailman/listinfo/qemu-devel > > _______________________________________________ Qemu-devel mailing list Qemu-devel@nongnu.org http://lists.nongnu.org/mailman/listinfo/qemu-devel
