Michael S. Tsirkin
2023-Apr-11 06:55 UTC
[PATCH] virtio_pci: Wait for legacy device to be reset
On Tue, Apr 11, 2023 at 06:49:03AM +0000, Angus Chen wrote:> > > > -----Original Message----- > > From: Michael S. Tsirkin <mst at redhat.com> > > Sent: Tuesday, April 11, 2023 2:47 PM > > To: Angus Chen <angus.chen at jaguarmicro.com> > > Cc: Jason Wang <jasowang at redhat.com>; > > virtualization at lists.linux-foundation.org; linux-kernel at vger.kernel.org > > Subject: Re: [PATCH] virtio_pci: Wait for legacy device to be reset > > > > On Tue, Apr 11, 2023 at 06:36:39AM +0000, Angus Chen wrote: > > > Hi. > > > > > > > -----Original Message----- > > > > From: Jason Wang <jasowang at redhat.com> > > > > Sent: Tuesday, April 11, 2023 1:24 PM > > > > To: Angus Chen <angus.chen at jaguarmicro.com> > > > > Cc: mst at redhat.com; virtualization at lists.linux-foundation.org; > > > > linux-kernel at vger.kernel.org > > > > Subject: Re: [PATCH] virtio_pci: Wait for legacy device to be reset > > > > > > > > On Tue, Apr 11, 2023 at 9:39?AM Angus Chen > > <angus.chen at jaguarmicro.com> > > > > wrote: > > > > > > > > > > We read the status of device after reset, > > > > > It is not guaranteed that the device be reseted successfully. > > > > > We can use a while loop to make sure that,like the modern device did. > > > > > The spec is not request it ,but it work. > > > > > > > > The only concern is if it's too late to do this. > > > > > > > > Btw, any reason you want to have a legacy hardware implementation. It > > > > will be very tricky to work correctly. > > > En,I found this in the real production environment some times about one > > year ago. > > > and I fix this out of tree.our virtio card had been sold about thousands . > > > > > > Now,we created a new card, it support virtio 0.95,1.0,1.1 etc. > > > > I am not 100% sure what does this mean. > > So it's a transitional device then? > Hi mst,it is a real card in the In cloud computing ,not transitional device.yes, a real card. But you said it supports 0.95, 1.0 and 1.1 guests, so this is what the virtio spec calls a transitional device, right? To simplify transition from these earlier draft interfaces, a device MAY implement: \begin{description} \item[Transitional Device] a device supporting both drivers conforming to this specification, and allowing legacy drivers. \end{description} or did I misunderstand?> > > > > > > And we use this host vdpa+ legacy virtio in vm to hot migration,we found > > that the > > > Legacy model often get the middle state value after reset and probe again. > > > The Soc is Simulated by fpga which is run slower than the host,so the same > > bug > > > Is found more frequently when the host use the other kernel like ubuntu or > > centos8. > > > > > > So we hope we can fix this by upstream . > > > > > > > > Thanks > > > > > > > > > > > > > > Signed-off-by: Angus Chen <angus.chen at jaguarmicro.com> > > > > > --- > > > > > drivers/virtio/virtio_pci_legacy.c | 4 +++- > > > > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > > > > > > > diff --git a/drivers/virtio/virtio_pci_legacy.c > > b/drivers/virtio/virtio_pci_legacy.c > > > > > index 2257f1b3d8ae..f2d241563e4f 100644 > > > > > --- a/drivers/virtio/virtio_pci_legacy.c > > > > > +++ b/drivers/virtio/virtio_pci_legacy.c > > > > > @@ -14,6 +14,7 @@ > > > > > * Michael S. Tsirkin <mst at redhat.com> > > > > > */ > > > > > > > > > > +#include <linux/delay.h> > > > > > #include "linux/virtio_pci_legacy.h" > > > > > #include "virtio_pci_common.h" > > > > > > > > > > @@ -97,7 +98,8 @@ static void vp_reset(struct virtio_device *vdev) > > > > > vp_legacy_set_status(&vp_dev->ldev, 0); > > > > > /* Flush out the status write, and flush in device writes, > > > > > * including MSi-X interrupts, if any. */ > > > > > - vp_legacy_get_status(&vp_dev->ldev); > > > > > + while (vp_legacy_get_status(&vp_dev->ldev)) > > > > > + msleep(1); > > > > > /* Flush pending VQ/configuration callbacks. */ > > > > > vp_synchronize_vectors(vdev); > > > > > } > > > > > -- > > > > > 2.25.1 > > > > > > > > >