From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54888) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aBHKm-00061I-AH for qemu-devel@nongnu.org; Tue, 22 Dec 2015 02:26:13 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aBHKh-0004np-9G for qemu-devel@nongnu.org; Tue, 22 Dec 2015 02:26:12 -0500 Received: from [59.151.112.132] (port=14752 helo=heian.cn.fujitsu.com) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aBHKg-0004ZT-9L for qemu-devel@nongnu.org; Tue, 22 Dec 2015 02:26:07 -0500 Message-ID: <5678F955.6010703@cn.fujitsu.com> Date: Tue, 22 Dec 2015 15:18:45 +0800 From: Chen Fan MIME-Version: 1.0 References: <35d75210aef922bd049d93e0c8dbe13a2b5b1dd3.1447748073.git.chen.fan.fnst@cn.fujitsu.com> <1450384318.2674.110.camel@redhat.com> <56737D85.3030305@cn.fujitsu.com> <1450732026.3781.89.camel@redhat.com> In-Reply-To: <1450732026.3781.89.camel@redhat.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v14 Resend 10/13] pci: add pci device pre-post reset callbacks for host bus reset List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alex Williamson , Cao jin , qemu-devel@nongnu.org Cc: mst@redhat.com On 12/22/2015 05:07 AM, Alex Williamson wrote: > On Fri, 2015-12-18 at 11:29 +0800, Chen Fan wrote: >> On 12/18/2015 04:31 AM, Alex Williamson wrote: >>> On Thu, 2015-12-17 at 09:41 +0800, Cao jin wrote: >>>> From: Chen Fan >>>> >>>> Particularly, For vfio devices, Once need to recovery devices >>>> by bus reset such as AER, we always need to reset the host bus >>>> to recovery the devices under the bus, so we need to add pci >>>> device >>>> callbacks to specify to do host bus reset. >>>> >>>> Signed-off-by: Chen Fan >>>> Reviewed-by: Michael S. Tsirkin >>>> --- >>>> hw/pci/pci.c | 18 ++++++++++++++++++ >>>> hw/pci/pci_bridge.c | 9 +++++++++ >>>> hw/vfio/pci.c | 26 ++++++++++++++++++++++++++ >>>> hw/vfio/pci.h | 2 ++ >>>> include/hw/pci/pci.h | 7 +++++++ >>>> 5 files changed, 62 insertions(+) >>>> >>>> diff --git a/hw/pci/pci.c b/hw/pci/pci.c >>>> index f6ca6ef..64fa2cc 100644 >>>> --- a/hw/pci/pci.c >>>> +++ b/hw/pci/pci.c >>>> @@ -247,6 +247,24 @@ static void pci_do_device_reset(PCIDevice >>>> *dev) >>>> msix_reset(dev); >>>> } >>>> >>>> +void pci_device_pre_reset(PCIBus *bus, PCIDevice *dev, void >>>> *unused) >>>> +{ >>>> + PCIDeviceClass *dc = PCI_DEVICE_GET_CLASS(dev); >>>> + >>>> + if (dc->pre_reset) { >>>> + dc->pre_reset(dev); >>>> + } >>>> +} >>>> + >>>> +void pci_device_post_reset(PCIBus *bus, PCIDevice *dev, void >>>> *unused) >>>> +{ >>>> + PCIDeviceClass *dc = PCI_DEVICE_GET_CLASS(dev); >>>> + >>>> + if (dc->post_reset) { >>>> + dc->post_reset(dev); >>>> + } >>>> +} >>>> + >>>> /* >>>> * This function is called on #RST and FLR. >>>> * FLR if PCI_EXP_DEVCTL_BCR_FLR is set >>>> diff --git a/hw/pci/pci_bridge.c b/hw/pci/pci_bridge.c >>>> index 40c97b1..ddb76ab 100644 >>>> --- a/hw/pci/pci_bridge.c >>>> +++ b/hw/pci/pci_bridge.c >>>> @@ -267,8 +267,17 @@ void pci_bridge_write_config(PCIDevice *d, >>>> >>>> newctl = pci_get_word(d->config + PCI_BRIDGE_CONTROL); >>>> if (~oldctl & newctl & PCI_BRIDGE_CTL_BUS_RESET) { >>>> + /* >>>> + * Notify all vfio-pci devices under the bus >>>> + * should do physical bus reset. >>>> + */ >>>> + PCIBus *sec_bus = pci_bridge_get_sec_bus(s); >>>> + pci_for_each_device(sec_bus, pci_bus_num(sec_bus), >>>> + pci_device_pre_reset, NULL); >>>> /* Trigger hot reset on 0->1 transition. */ >>>> qbus_reset_all(&s->sec_bus.qbus); >>>> + pci_for_each_device(sec_bus, pci_bus_num(sec_bus), >>>> + pci_device_post_reset, NULL); >>>> } >>>> } >>>> >>>> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c >>>> index e17dc89..df32618 100644 >>>> --- a/hw/vfio/pci.c >>>> +++ b/hw/vfio/pci.c >>>> @@ -39,6 +39,7 @@ >>>> >>>> static void vfio_disable_interrupts(VFIOPCIDevice *vdev); >>>> static void vfio_mmap_set_enabled(VFIOPCIDevice *vdev, bool >>>> enabled); >>>> +static int vfio_pci_hot_reset(VFIOPCIDevice *vdev, bool single); >>>> >>>> /* >>>> * Disabling BAR mmaping can be slow, but toggling it around >>>> INTx >>>> can >>>> @@ -1888,6 +1889,8 @@ static int >>>> vfio_check_host_bus_reset(VFIOPCIDevice *vdev) >>>> /* List all affected devices by bus reset */ >>>> devices = &info->devices[0]; >>>> >>>> + vdev->single_depend_dev = (info->count == 1); >>>> + >>>> /* Verify that we have all the groups required */ >>>> for (i = 0; i < info->count; i++) { >>>> PCIHostDeviceAddress host; >>>> @@ -2029,10 +2032,26 @@ static int >>>> vfio_check_bus_reset(NotifierWithReturn *n, void *opaque) >>>> return vfio_check_host_bus_reset(vdev); >>>> } >>>> >>>> +static void vfio_aer_pre_reset(PCIDevice *pdev) >>>> +{ >>>> + VFIOPCIDevice *vdev = DO_UPCAST(VFIOPCIDevice, pdev, pdev); >>>> + >>>> + vdev->aer_reset = true; >>>> + vfio_pci_hot_reset(vdev, vdev->single_depend_dev); >>>> +} >>> Doesn't this lead to multiple host bus resets per guest bus reset >>> in >>> many cases? It looks like we'll do it once per vfio-pci device, >>> even >>> if those devices are on the same host bus. That's a 1 second >>> operation >>> per device. Can we avoid that? Maybe some sort of sequence ID >>> could >>> help a device figure out whether it's already been reset as part of >>> a >>> dependent device for this particular guest bus reset. Thanks, >> That's right, I missed this case, but I don't understand the scenario >> how to >> use a sequence ID to mark the device if been reset. can you detail it >> ? > I don't really have a concrete idea for a sequence ID, it was just a > thought that maybe if each bus reset had a sequence ID then devices > could know whether they've already been reset for that sequence ID. > The basic problem we have is that reset callbacks are per device and > it's difficult to infer which individual resets are part of that bus > reset. In fact, do we propagate resets correctly down secondary > bridges? We're triggering off a VM write of the bridge control bus > reset bit triggering from 0->1 and we then call qbus_reset_all() on > that qbus, which I think is just going to call pci_bridge_reset() for > any other bridges, which doesn't do anything about resetting deeper > subordinate buses. I think that means that if we had a root port with > a switch below it and endpoints below that, if the VM triggered a > secondary bus reset at the root port, the endpoints would never see it, > which is not how real hardware works. Indeed, you're right, for subordinate buses reset, we should have a common mechanism for all bridges. > >> additional, there was a mechanism to compute device whether need to >> be reset >> by hot reset. so I simply modify the code as the following: >> >> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c >> index a9bc67e..42774ca 100644 >> --- a/hw/vfio/pci.c >> +++ b/hw/vfio/pci.c >> @@ -2063,13 +2063,19 @@ static void vfio_aer_pre_reset(PCIDevice >> *pdev) >> VFIOPCIDevice *vdev = DO_UPCAST(VFIOPCIDevice, pdev, pdev); >> >> vdev->aer_reset = true; >> - vfio_pci_hot_reset(vdev, vdev->single_depend_dev); >> + vdev->vbasedev.needs_reset = true; >> } >> >> static void vfio_aer_post_reset(PCIDevice *pdev) >> { >> VFIOPCIDevice *vdev = DO_UPCAST(VFIOPCIDevice, pdev, pdev); >> >> + if (!vdev->single_depend_dev && vdev->vbasedev.needs_reset) { >> + vfio_pci_hot_reset(vdev, false); >> + } else { >> + vfio_pci_hot_reset(vdev, true); >> + } >> + >> vdev->aer_reset = false; >> } >> >> what do you think of this ? > I think it might be a bigger problem than that subtle change. I wonder > if we really need a better model of the reset line through the > subordinate buses. When reset is asserted, we'd set a bus_in_reset > flag on the bus and trigger downstream bridges to do the same. Then > when the user de-asserts reset, we'd call qbus_reset_all() and > propagate it through to downstream buses. That way the per device > reset callback could check to see if the bus is in reset and aer > devices can then know to do a bus reset. Finally, the bus_in_reset > flag would be cleared on all the affected buses. I'm sure there are > numerous details missing there, but it seems like it might be a > reasonable approach. Thanks, it should be, let me try to think about it carefully.;) Thanks, Chen > > Alex > > > . >