* [PATCH v2] virtio: Add polling virtio-mmio device reset completion @ 2024-09-26 2:25 Jianguo Sun 2024-09-26 3:21 ` Jason Wang 0 siblings, 1 reply; 7+ messages in thread From: Jianguo Sun @ 2024-09-26 2:25 UTC (permalink / raw) To: mst, jasowang, xuanzhuo, eperezma, virtualization Cc: Jianguo Sun, Sreenad Menon, Anant Goel We write 0 to device_status to initiate reset of a virtio-mmio device. The reset operation itself may or may not be completed by the time write instruction completes. Add polling device_status to return 0 to ensure reset completion before reinitializing the device. Change-Id: If15d11d090dfd0d4972ad35f49af03e076872413 Signed-off-by: Jianguo Sun <quic_jianguos@quicinc.com> Signed-off-by: Sreenad Menon <quic_sreemeno@quicinc.com> Signed-off-by: Anant Goel <quic_anantg@quicinc.com> --- drivers/virtio/virtio_mmio.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c index 90e784e7b721..cf1a4a3dd35d 100644 --- a/drivers/virtio/virtio_mmio.c +++ b/drivers/virtio/virtio_mmio.c @@ -70,6 +70,7 @@ #include <linux/virtio_config.h> #include <uapi/linux/virtio_mmio.h> #include <linux/virtio_ring.h> +#include <linux/delay.h> @@ -269,6 +270,11 @@ static void vm_reset(struct virtio_device *vdev) /* 0 status means a reset. */ writel(0, vm_dev->base + VIRTIO_MMIO_STATUS); + /* After writing 0 to device_status, the driver MUST wait for a read of + * device_status to return 0 before reinitializing the device. + */ + while (readl(vm_dev->base + VIRTIO_MMIO_STATUS)) + msleep(1); } -- 2.17.1 ^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH v2] virtio: Add polling virtio-mmio device reset completion 2024-09-26 2:25 [PATCH v2] virtio: Add polling virtio-mmio device reset completion Jianguo Sun @ 2024-09-26 3:21 ` Jason Wang 2024-09-26 6:09 ` Michael S. Tsirkin 0 siblings, 1 reply; 7+ messages in thread From: Jason Wang @ 2024-09-26 3:21 UTC (permalink / raw) To: Jianguo Sun Cc: mst, xuanzhuo, eperezma, virtualization, Sreenad Menon, Anant Goel On Thu, Sep 26, 2024 at 10:27 AM Jianguo Sun <quic_jianguos@quicinc.com> wrote: > > We write 0 to device_status to initiate reset of a virtio-mmio device. > The reset operation itself may or may not be completed by the time > write instruction completes. Add polling device_status to return > 0 to ensure reset completion before reinitializing the device. > > Change-Id: If15d11d090dfd0d4972ad35f49af03e076872413 > Signed-off-by: Jianguo Sun <quic_jianguos@quicinc.com> > Signed-off-by: Sreenad Menon <quic_sreemeno@quicinc.com> > Signed-off-by: Anant Goel <quic_anantg@quicinc.com> > --- > drivers/virtio/virtio_mmio.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c > index 90e784e7b721..cf1a4a3dd35d 100644 > --- a/drivers/virtio/virtio_mmio.c > +++ b/drivers/virtio/virtio_mmio.c > @@ -70,6 +70,7 @@ > #include <linux/virtio_config.h> > #include <uapi/linux/virtio_mmio.h> > #include <linux/virtio_ring.h> > +#include <linux/delay.h> > > > > @@ -269,6 +270,11 @@ static void vm_reset(struct virtio_device *vdev) > > /* 0 status means a reset. */ > writel(0, vm_dev->base + VIRTIO_MMIO_STATUS); > + /* After writing 0 to device_status, the driver MUST wait for a read of > + * device_status to return 0 before reinitializing the device. > + */ Is this copied from the spec? I can only see a similar description in the PCI but not MMIO part. > + while (readl(vm_dev->base + VIRTIO_MMIO_STATUS)) > + msleep(1); Again, we probably need a feature bit to unbreak existing MMIO devices? THanks > } > > > -- > 2.17.1 > ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v2] virtio: Add polling virtio-mmio device reset completion 2024-09-26 3:21 ` Jason Wang @ 2024-09-26 6:09 ` Michael S. Tsirkin 2024-09-27 4:08 ` Jason Wang 0 siblings, 1 reply; 7+ messages in thread From: Michael S. Tsirkin @ 2024-09-26 6:09 UTC (permalink / raw) To: Jason Wang Cc: Jianguo Sun, xuanzhuo, eperezma, virtualization, Sreenad Menon, Anant Goel On Thu, Sep 26, 2024 at 11:21:25AM +0800, Jason Wang wrote: > On Thu, Sep 26, 2024 at 10:27 AM Jianguo Sun <quic_jianguos@quicinc.com> wrote: > > > > We write 0 to device_status to initiate reset of a virtio-mmio device. > > The reset operation itself may or may not be completed by the time > > write instruction completes. Add polling device_status to return > > 0 to ensure reset completion before reinitializing the device. > > > > Change-Id: If15d11d090dfd0d4972ad35f49af03e076872413 > > Signed-off-by: Jianguo Sun <quic_jianguos@quicinc.com> > > Signed-off-by: Sreenad Menon <quic_sreemeno@quicinc.com> > > Signed-off-by: Anant Goel <quic_anantg@quicinc.com> > > --- > > drivers/virtio/virtio_mmio.c | 6 ++++++ > > 1 file changed, 6 insertions(+) > > > > diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c > > index 90e784e7b721..cf1a4a3dd35d 100644 > > --- a/drivers/virtio/virtio_mmio.c > > +++ b/drivers/virtio/virtio_mmio.c > > @@ -70,6 +70,7 @@ > > #include <linux/virtio_config.h> > > #include <uapi/linux/virtio_mmio.h> > > #include <linux/virtio_ring.h> > > +#include <linux/delay.h> > > > > > > > > @@ -269,6 +270,11 @@ static void vm_reset(struct virtio_device *vdev) > > > > /* 0 status means a reset. */ > > writel(0, vm_dev->base + VIRTIO_MMIO_STATUS); > > + /* After writing 0 to device_status, the driver MUST wait for a read of > > + * device_status to return 0 before reinitializing the device. > > + */ > > Is this copied from the spec? I can only see a similar description in > the PCI but not MMIO part. Not in spec. We can add something like this in spec, but it can not be a MUST, has to be a SHOULD. > > + while (readl(vm_dev->base + VIRTIO_MMIO_STATUS)) > > + msleep(1); > > Again, we probably need a feature bit to unbreak existing MMIO devices? > > THanks We can do this unconditionally since legacy devices return 0 immediately, feature negotiation happens after reset, won't be useful here. > > } > > > > > > -- > > 2.17.1 > > ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v2] virtio: Add polling virtio-mmio device reset completion 2024-09-26 6:09 ` Michael S. Tsirkin @ 2024-09-27 4:08 ` Jason Wang 2024-09-29 17:51 ` Michael S. Tsirkin 0 siblings, 1 reply; 7+ messages in thread From: Jason Wang @ 2024-09-27 4:08 UTC (permalink / raw) To: Michael S. Tsirkin Cc: Jianguo Sun, xuanzhuo, eperezma, virtualization, Sreenad Menon, Anant Goel On Thu, Sep 26, 2024 at 2:09 PM Michael S. Tsirkin <mst@redhat.com> wrote: > > On Thu, Sep 26, 2024 at 11:21:25AM +0800, Jason Wang wrote: > > On Thu, Sep 26, 2024 at 10:27 AM Jianguo Sun <quic_jianguos@quicinc.com> wrote: > > > > > > We write 0 to device_status to initiate reset of a virtio-mmio device. > > > The reset operation itself may or may not be completed by the time > > > write instruction completes. Add polling device_status to return > > > 0 to ensure reset completion before reinitializing the device. > > > > > > Change-Id: If15d11d090dfd0d4972ad35f49af03e076872413 > > > Signed-off-by: Jianguo Sun <quic_jianguos@quicinc.com> > > > Signed-off-by: Sreenad Menon <quic_sreemeno@quicinc.com> > > > Signed-off-by: Anant Goel <quic_anantg@quicinc.com> > > > --- > > > drivers/virtio/virtio_mmio.c | 6 ++++++ > > > 1 file changed, 6 insertions(+) > > > > > > diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c > > > index 90e784e7b721..cf1a4a3dd35d 100644 > > > --- a/drivers/virtio/virtio_mmio.c > > > +++ b/drivers/virtio/virtio_mmio.c > > > @@ -70,6 +70,7 @@ > > > #include <linux/virtio_config.h> > > > #include <uapi/linux/virtio_mmio.h> > > > #include <linux/virtio_ring.h> > > > +#include <linux/delay.h> > > > > > > > > > > > > @@ -269,6 +270,11 @@ static void vm_reset(struct virtio_device *vdev) > > > > > > /* 0 status means a reset. */ > > > writel(0, vm_dev->base + VIRTIO_MMIO_STATUS); > > > + /* After writing 0 to device_status, the driver MUST wait for a read of > > > + * device_status to return 0 before reinitializing the device. > > > + */ > > > > Is this copied from the spec? I can only see a similar description in > > the PCI but not MMIO part. > > Not in spec. We can add something like this in spec, but it > can not be a MUST, has to be a SHOULD. > > > > + while (readl(vm_dev->base + VIRTIO_MMIO_STATUS)) > > > + msleep(1); > > > > Again, we probably need a feature bit to unbreak existing MMIO devices? > > > > THanks > > We can do this unconditionally since legacy devices return 0 > immediately, The problem is that we can't audit all legacy device implementations. Current driver still works if a device doesn't reset status to 0. > feature negotiation happens after reset, won't be useful > here. Right, as said in another thread, it could be mmio specific flag or version. Thanks > > > > > } > > > > > > > > > -- > > > 2.17.1 > > > > ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v2] virtio: Add polling virtio-mmio device reset completion 2024-09-27 4:08 ` Jason Wang @ 2024-09-29 17:51 ` Michael S. Tsirkin 2024-10-09 8:24 ` Jason Wang 0 siblings, 1 reply; 7+ messages in thread From: Michael S. Tsirkin @ 2024-09-29 17:51 UTC (permalink / raw) To: Jason Wang Cc: Jianguo Sun, xuanzhuo, eperezma, virtualization, Sreenad Menon, Anant Goel On Fri, Sep 27, 2024 at 12:08:34PM +0800, Jason Wang wrote: > On Thu, Sep 26, 2024 at 2:09 PM Michael S. Tsirkin <mst@redhat.com> wrote: > > > > On Thu, Sep 26, 2024 at 11:21:25AM +0800, Jason Wang wrote: > > > On Thu, Sep 26, 2024 at 10:27 AM Jianguo Sun <quic_jianguos@quicinc.com> wrote: > > > > > > > > We write 0 to device_status to initiate reset of a virtio-mmio device. > > > > The reset operation itself may or may not be completed by the time > > > > write instruction completes. Add polling device_status to return > > > > 0 to ensure reset completion before reinitializing the device. > > > > > > > > Change-Id: If15d11d090dfd0d4972ad35f49af03e076872413 > > > > Signed-off-by: Jianguo Sun <quic_jianguos@quicinc.com> > > > > Signed-off-by: Sreenad Menon <quic_sreemeno@quicinc.com> > > > > Signed-off-by: Anant Goel <quic_anantg@quicinc.com> > > > > --- > > > > drivers/virtio/virtio_mmio.c | 6 ++++++ > > > > 1 file changed, 6 insertions(+) > > > > > > > > diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c > > > > index 90e784e7b721..cf1a4a3dd35d 100644 > > > > --- a/drivers/virtio/virtio_mmio.c > > > > +++ b/drivers/virtio/virtio_mmio.c > > > > @@ -70,6 +70,7 @@ > > > > #include <linux/virtio_config.h> > > > > #include <uapi/linux/virtio_mmio.h> > > > > #include <linux/virtio_ring.h> > > > > +#include <linux/delay.h> > > > > > > > > > > > > > > > > @@ -269,6 +270,11 @@ static void vm_reset(struct virtio_device *vdev) > > > > > > > > /* 0 status means a reset. */ > > > > writel(0, vm_dev->base + VIRTIO_MMIO_STATUS); > > > > + /* After writing 0 to device_status, the driver MUST wait for a read of > > > > + * device_status to return 0 before reinitializing the device. > > > > + */ > > > > > > Is this copied from the spec? I can only see a similar description in > > > the PCI but not MMIO part. > > > > Not in spec. We can add something like this in spec, but it > > can not be a MUST, has to be a SHOULD. > > > > > > + while (readl(vm_dev->base + VIRTIO_MMIO_STATUS)) > > > > + msleep(1); > > > > > > Again, we probably need a feature bit to unbreak existing MMIO devices? > > > > > > THanks > > > > We can do this unconditionally since legacy devices return 0 > > immediately, > > The problem is that we can't audit all legacy device implementations. > Current driver still works if a device doesn't reset status to 0. These would be out of spec though, would they not? The reset value for the register is 0, and it is R/W. > > feature negotiation happens after reset, won't be useful > > here. > > Right, as said in another thread, it could be mmio specific flag or version. > > Thanks > > > > > > > > > } > > > > > > > > > > > > -- > > > > 2.17.1 > > > > > > ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v2] virtio: Add polling virtio-mmio device reset completion 2024-09-29 17:51 ` Michael S. Tsirkin @ 2024-10-09 8:24 ` Jason Wang 2024-10-09 9:31 ` Michael S. Tsirkin 0 siblings, 1 reply; 7+ messages in thread From: Jason Wang @ 2024-10-09 8:24 UTC (permalink / raw) To: Michael S. Tsirkin Cc: Jianguo Sun, xuanzhuo, eperezma, virtualization, Sreenad Menon, Anant Goel On Mon, Sep 30, 2024 at 1:51 AM Michael S. Tsirkin <mst@redhat.com> wrote: > > On Fri, Sep 27, 2024 at 12:08:34PM +0800, Jason Wang wrote: > > On Thu, Sep 26, 2024 at 2:09 PM Michael S. Tsirkin <mst@redhat.com> wrote: > > > > > > On Thu, Sep 26, 2024 at 11:21:25AM +0800, Jason Wang wrote: > > > > On Thu, Sep 26, 2024 at 10:27 AM Jianguo Sun <quic_jianguos@quicinc.com> wrote: > > > > > > > > > > We write 0 to device_status to initiate reset of a virtio-mmio device. > > > > > The reset operation itself may or may not be completed by the time > > > > > write instruction completes. Add polling device_status to return > > > > > 0 to ensure reset completion before reinitializing the device. > > > > > > > > > > Change-Id: If15d11d090dfd0d4972ad35f49af03e076872413 > > > > > Signed-off-by: Jianguo Sun <quic_jianguos@quicinc.com> > > > > > Signed-off-by: Sreenad Menon <quic_sreemeno@quicinc.com> > > > > > Signed-off-by: Anant Goel <quic_anantg@quicinc.com> > > > > > --- > > > > > drivers/virtio/virtio_mmio.c | 6 ++++++ > > > > > 1 file changed, 6 insertions(+) > > > > > > > > > > diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c > > > > > index 90e784e7b721..cf1a4a3dd35d 100644 > > > > > --- a/drivers/virtio/virtio_mmio.c > > > > > +++ b/drivers/virtio/virtio_mmio.c > > > > > @@ -70,6 +70,7 @@ > > > > > #include <linux/virtio_config.h> > > > > > #include <uapi/linux/virtio_mmio.h> > > > > > #include <linux/virtio_ring.h> > > > > > +#include <linux/delay.h> > > > > > > > > > > > > > > > > > > > > @@ -269,6 +270,11 @@ static void vm_reset(struct virtio_device *vdev) > > > > > > > > > > /* 0 status means a reset. */ > > > > > writel(0, vm_dev->base + VIRTIO_MMIO_STATUS); > > > > > + /* After writing 0 to device_status, the driver MUST wait for a read of > > > > > + * device_status to return 0 before reinitializing the device. > > > > > + */ > > > > > > > > Is this copied from the spec? I can only see a similar description in > > > > the PCI but not MMIO part. > > > > > > Not in spec. We can add something like this in spec, but it > > > can not be a MUST, has to be a SHOULD. > > > > > > > > + while (readl(vm_dev->base + VIRTIO_MMIO_STATUS)) > > > > > + msleep(1); > > > > > > > > Again, we probably need a feature bit to unbreak existing MMIO devices? > > > > > > > > THanks > > > > > > We can do this unconditionally since legacy devices return 0 > > > immediately, > > > > The problem is that we can't audit all legacy device implementations. > > Current driver still works if a device doesn't reset status to 0. > > These would be out of spec though, would they not? Yes, but it would work. Should we care about those? > The reset value for the register is 0, and it is R/W. > > > > > feature negotiation happens after reset, won't be useful > > > here. > > > > Right, as said in another thread, it could be mmio specific flag or version. > > > > Thanks > > > > > > > > > > > > > } > > > > > > > > > > > > > > > -- > > > > > 2.17.1 > > > > > > > > > Thanks ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v2] virtio: Add polling virtio-mmio device reset completion 2024-10-09 8:24 ` Jason Wang @ 2024-10-09 9:31 ` Michael S. Tsirkin 0 siblings, 0 replies; 7+ messages in thread From: Michael S. Tsirkin @ 2024-10-09 9:31 UTC (permalink / raw) To: Jason Wang Cc: Jianguo Sun, xuanzhuo, eperezma, virtualization, Sreenad Menon, Anant Goel On Wed, Oct 09, 2024 at 04:24:38PM +0800, Jason Wang wrote: > On Mon, Sep 30, 2024 at 1:51 AM Michael S. Tsirkin <mst@redhat.com> wrote: > > > > On Fri, Sep 27, 2024 at 12:08:34PM +0800, Jason Wang wrote: > > > On Thu, Sep 26, 2024 at 2:09 PM Michael S. Tsirkin <mst@redhat.com> wrote: > > > > > > > > On Thu, Sep 26, 2024 at 11:21:25AM +0800, Jason Wang wrote: > > > > > On Thu, Sep 26, 2024 at 10:27 AM Jianguo Sun <quic_jianguos@quicinc.com> wrote: > > > > > > > > > > > > We write 0 to device_status to initiate reset of a virtio-mmio device. > > > > > > The reset operation itself may or may not be completed by the time > > > > > > write instruction completes. Add polling device_status to return > > > > > > 0 to ensure reset completion before reinitializing the device. > > > > > > > > > > > > Change-Id: If15d11d090dfd0d4972ad35f49af03e076872413 > > > > > > Signed-off-by: Jianguo Sun <quic_jianguos@quicinc.com> > > > > > > Signed-off-by: Sreenad Menon <quic_sreemeno@quicinc.com> > > > > > > Signed-off-by: Anant Goel <quic_anantg@quicinc.com> > > > > > > --- > > > > > > drivers/virtio/virtio_mmio.c | 6 ++++++ > > > > > > 1 file changed, 6 insertions(+) > > > > > > > > > > > > diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c > > > > > > index 90e784e7b721..cf1a4a3dd35d 100644 > > > > > > --- a/drivers/virtio/virtio_mmio.c > > > > > > +++ b/drivers/virtio/virtio_mmio.c > > > > > > @@ -70,6 +70,7 @@ > > > > > > #include <linux/virtio_config.h> > > > > > > #include <uapi/linux/virtio_mmio.h> > > > > > > #include <linux/virtio_ring.h> > > > > > > +#include <linux/delay.h> > > > > > > > > > > > > > > > > > > > > > > > > @@ -269,6 +270,11 @@ static void vm_reset(struct virtio_device *vdev) > > > > > > > > > > > > /* 0 status means a reset. */ > > > > > > writel(0, vm_dev->base + VIRTIO_MMIO_STATUS); > > > > > > + /* After writing 0 to device_status, the driver MUST wait for a read of > > > > > > + * device_status to return 0 before reinitializing the device. > > > > > > + */ > > > > > > > > > > Is this copied from the spec? I can only see a similar description in > > > > > the PCI but not MMIO part. > > > > > > > > Not in spec. We can add something like this in spec, but it > > > > can not be a MUST, has to be a SHOULD. > > > > > > > > > > + while (readl(vm_dev->base + VIRTIO_MMIO_STATUS)) > > > > > > + msleep(1); > > > > > > > > > > Again, we probably need a feature bit to unbreak existing MMIO devices? > > > > > > > > > > THanks > > > > > > > > We can do this unconditionally since legacy devices return 0 > > > > immediately, > > > > > > The problem is that we can't audit all legacy device implementations. > > > Current driver still works if a device doesn't reset status to 0. > > > > These would be out of spec though, would they not? > > Yes, but it would work. Should we care about those? Not unless there's an actual, common device that does it. > > The reset value for the register is 0, and it is R/W. > > > > > > > > feature negotiation happens after reset, won't be useful > > > > here. > > > > > > Right, as said in another thread, it could be mmio specific flag or version. > > > > > > Thanks > > > > > > > > > > > > > > > > > } > > > > > > > > > > > > > > > > > > -- > > > > > > 2.17.1 > > > > > > > > > > > > > > Thanks ^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2024-10-09 9:31 UTC | newest] Thread overview: 7+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2024-09-26 2:25 [PATCH v2] virtio: Add polling virtio-mmio device reset completion Jianguo Sun 2024-09-26 3:21 ` Jason Wang 2024-09-26 6:09 ` Michael S. Tsirkin 2024-09-27 4:08 ` Jason Wang 2024-09-29 17:51 ` Michael S. Tsirkin 2024-10-09 8:24 ` Jason Wang 2024-10-09 9:31 ` Michael S. Tsirkin
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for NNTP newsgroup(s).