From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45879) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XRe0Z-0001J3-UC for qemu-devel@nongnu.org; Wed, 10 Sep 2014 05:16:18 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XRe0S-0000Rs-Sl for qemu-devel@nongnu.org; Wed, 10 Sep 2014 05:16:11 -0400 Received: from e28smtp01.in.ibm.com ([122.248.162.1]:40679) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XRe0R-0000RH-NG for qemu-devel@nongnu.org; Wed, 10 Sep 2014 05:16:04 -0400 Received: from /spool/local by e28smtp01.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 10 Sep 2014 14:45:59 +0530 From: Nikunj A Dadhania In-Reply-To: <20140910093230.GB7902@redhat.com> References: <1410192283-4026-1-git-send-email-mst@redhat.com> <20140910003532.22d72602@bahia.local> <87oaunops6.fsf@abhimanyu.in.ibm.com> <20140910093230.GB7902@redhat.com> Date: Wed, 10 Sep 2014 14:45:51 +0530 Message-ID: <87k35bomyg.fsf@abhimanyu.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [Qemu-devel] [PATCH] virtio-pci: enable bus master for old guests List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: Alexey Kardashevskiy , Jan Kiszka , qemu-stable@nongnu.org, qemu-devel@nongnu.org, Anthony Liguori "Michael S. Tsirkin" writes: > On Wed, Sep 10, 2014 at 01:44:49PM +0530, Nikunj A Dadhania wrote: >> Greg Kurz writes: >> >> > On Mon, 8 Sep 2014 19:05:02 +0300 >> > "Michael S. Tsirkin" wrote: >> > >> >> commit cc943c36faa192cd4b32af8fe5edb31894017d35 >> >> pci: Use bus master address space for delivering MSI/MSI-X messages >> >> breaks virtio-net for rhel6.[56] x86 guests because they don't >> >> enable bus mastering for virtio PCI devices >> >> >> >> Old guests forgot to enable bus mastering, enable it >> >> automatically on DRIVER_OK. >> >> >> >> Note: we should either back out the original patch from >> >> stable or apply this one on top. >> >> >> >> Cc: qemu-stable@nongnu.org >> >> Reported-by: Greg Kurz >> >> Signed-off-by: Jan Kiszka >> >> Signed-off-by: Michael S. Tsirkin >> >> --- >> >> hw/virtio/virtio-pci.c | 2 ++ >> >> 1 file changed, 2 insertions(+) >> >> >> >> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c >> >> index ddb5da1..af937d2 100644 >> >> --- a/hw/virtio/virtio-pci.c >> >> +++ b/hw/virtio/virtio-pci.c >> >> @@ -320,6 +320,8 @@ static void virtio_ioport_write(void *opaque, uint32_t addr, uint32_t val) >> >> if ((val & VIRTIO_CONFIG_S_DRIVER_OK) && >> >> !(proxy->pci_dev.config[PCI_COMMAND] & PCI_COMMAND_MASTER)) { >> >> proxy->flags |= VIRTIO_PCI_FLAG_BUS_MASTER_BUG; >> >> + memory_region_set_enabled(&proxy->pci_dev.bus_master_enable_region, >> >> + true); >> >> } >> >> break; >> >> case VIRTIO_MSI_CONFIG_VECTOR: >> > >> > Cc'ing Alexey for some SLOF and early boot of the ppc64 kernel expertise. >> > >> > Michael, >> > >> > This was enough to fix virtio-net in the rhel6.5 x86 guest case. Unfortunately, >> > this fails for rhel6.5 ppc64 because it is never called... >> >> > I did some debugging: it looks like the guest kernel calls the OF >> > quisece call to flush pending DMA and disables bus master on the >> > virtio-blk device (PCI_COMMAND == 0x3). >> >> Getting confused, above you are talking about virtio-net and here it is >> virtio-blk. >> >> Anyways, the routines still remains same for both of them. From SLOF >> during init we set DRIVER_OK, and after using the device during the >> quiesce, called from linux kernel VIRTIO_CONFIG_S_FAILED is set and then >> a VIRTIO_DEVICE_RESET is done. > > BTW, you really should start enabling bus mastering, avoid relying > on the work-around we have for broken guests. In SLOF, we do enable PCI MASTER during device scanning and then later disable it. Regards Nikunj