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Message-ID: <TY2PR06MB3424185F07F76D82746B6503859A9@TY2PR06MB3424.apcprd06.prod.outlook.com>
Date: Tue, 11 Apr 2023 10:57:51 +0000
From: Angus Chen <angus.chen@...uarmicro.com>
To: "Michael S. Tsirkin" <mst@...hat.com>
CC: Jason Wang <jasowang@...hat.com>,
"virtualization@...ts.linux-foundation.org"
<virtualization@...ts.linux-foundation.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] virtio_pci: Wait for legacy device to be reset
Hi mst.
> -----Original Message-----
> From: Michael S. Tsirkin <mst@...hat.com>
> Sent: Tuesday, April 11, 2023 6:16 PM
> To: Angus Chen <angus.chen@...uarmicro.com>
> Cc: Jason Wang <jasowang@...hat.com>;
> virtualization@...ts.linux-foundation.org; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH] virtio_pci: Wait for legacy device to be reset
>
> On Tue, Apr 11, 2023 at 07:30:48AM +0000, Angus Chen wrote:
> >
> >
> > > -----Original Message-----
> > > From: Michael S. Tsirkin <mst@...hat.com>
> > > Sent: Tuesday, April 11, 2023 3:21 PM
> > > To: Angus Chen <angus.chen@...uarmicro.com>
> > > Cc: Jason Wang <jasowang@...hat.com>;
> > > virtualization@...ts.linux-foundation.org; linux-kernel@...r.kernel.org
> > > Subject: Re: [PATCH] virtio_pci: Wait for legacy device to be reset
> > >
> > > On Tue, Apr 11, 2023 at 07:17:14AM +0000, Angus Chen wrote:
> > > >
> > > >
> > > > > -----Original Message-----
> > > > > From: Michael S. Tsirkin <mst@...hat.com>
> > > > > Sent: Tuesday, April 11, 2023 2:56 PM
> > > > > To: Angus Chen <angus.chen@...uarmicro.com>
> > > > > Cc: Jason Wang <jasowang@...hat.com>;
> > > > > virtualization@...ts.linux-foundation.org; linux-kernel@...r.kernel.org
> > > > > Subject: Re: [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@...hat.com>
> > > > > > > Sent: Tuesday, April 11, 2023 2:47 PM
> > > > > > > To: Angus Chen <angus.chen@...uarmicro.com>
> > > > > > > Cc: Jason Wang <jasowang@...hat.com>;
> > > > > > > virtualization@...ts.linux-foundation.org;
> linux-kernel@...r.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@...hat.com>
> > > > > > > > > Sent: Tuesday, April 11, 2023 1:24 PM
> > > > > > > > > To: Angus Chen <angus.chen@...uarmicro.com>
> > > > > > > > > Cc: mst@...hat.com; virtualization@...ts.linux-foundation.org;
> > > > > > > > > linux-kernel@...r.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@...uarmicro.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?
> > > > >
> > > > Yes, I'm not sure whether I make myself clear.
> > > > We support the vritio spec 0.95, 1.0 and 1.1 in the same card.
> > > > And the numer of devices is 1k per one card.
> > > >
> > > > Btw, thanks a lot for the work of redhat, we just Implement the virtio
> protocol
> > > by hardware.
> > >
> > > Yes, not very clear still. What are the device and vendor ID of the
> > > card? Does it have the virtio capabilities?
> > > Thanks
> > It's have the virtio capabilities.
> > When it is used in bare metal ，
> > it just use PCI_VENDOR_ID_REDHAT_QUMRANET.
> > When it use in vm,
> > It is just like :
> > { PCI_DEVICE_SUB(PCI_VENDOR_ID_REDHAT_QUMRANET,
> > VIRTIO_TRANS_ID_NET,
> > PCI_VENDOR_ID_JAGUARMICRO,
> > VIRTIO_ID_NET) },
> > { PCI_DEVICE_SUB(PCI_VENDOR_ID_REDHAT_QUMRANET,
> > VIRTIO_TRANS_ID_BLOCK,
> > PCI_VENDOR_ID_JAGUARMICRO,
> > VIRTIO_ID_BLOCK) },
> >
>
> Okay. So it's a transitional device. The question, then,
> is how come you end up with drivers/virtio/virtio_pci_legacy.c
> with a modern linux at all?
> Did you by chance set force_legacy = true ?
Yes,I can provide more information about it.
We can test it use force_legacy ,or we use a server with multi os but it use only one card.
Thanks.
>
>
> > >
> > > > >
> > > > > > >
> > > > > > >
> > > > > > > > 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@...uarmicro.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@...hat.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
> > > > > > > > > >
> > > > > > > >
> > > > > >
> > > >
> >
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