Re: [virtio-dev] [PATCH] virtio: support VIRTIO_F_ORDER_PLATFORM
On Wed, Jan 23, 2019 at 02:56:00PM +0800, Jason Wang wrote:
>
> On 2019/1/23 上午11:49, Michael S. Tsirkin wrote:
> > On Wed, Jan 23, 2019 at 11:08:04AM +0800, Jason Wang wrote:
> > > On 2019/1/23 上午1:03, Tiwei Bie wrote:
> > > > This patch introduces the support for VIRTIO_F_ORDER_PLATFORM.
> > > > When this feature is negotiated, driver will use the barriers
> > > > suitable for hardware devices.
> > > >
> > > > Signed-off-by: Tiwei Bie
> > > > ---
> > > >drivers/virtio/virtio_ring.c | 8
> > > >include/uapi/linux/virtio_config.h | 6 ++
> > > >2 files changed, 14 insertions(+)
> > > >
> > > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> > > > index cd7e755484e3..27d3f057493e 100644
> > > > --- a/drivers/virtio/virtio_ring.c
> > > > +++ b/drivers/virtio/virtio_ring.c
> > > > @@ -1609,6 +1609,9 @@ static struct virtqueue
> > > > *vring_create_virtqueue_packed(
> > > > !context;
> > > > vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX);
> > > > + if (virtio_has_feature(vdev, VIRTIO_F_ORDER_PLATFORM))
> > > > + vq->weak_barriers = false;
> > > > +
> > > > vq->packed.ring_dma_addr = ring_dma_addr;
> > > > vq->packed.driver_event_dma_addr = driver_event_dma_addr;
> > > > vq->packed.device_event_dma_addr = device_event_dma_addr;
> > > > @@ -2079,6 +2082,9 @@ struct virtqueue *__vring_new_virtqueue(unsigned
> > > > int index,
> > > > !context;
> > > > vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX);
> > > > + if (virtio_has_feature(vdev, VIRTIO_F_ORDER_PLATFORM))
> > > > + vq->weak_barriers = false;
> > > > +
> > > > vq->split.queue_dma_addr = 0;
> > > > vq->split.queue_size_in_bytes = 0;
> > > > @@ -2213,6 +2219,8 @@ void vring_transport_features(struct
> > > > virtio_device *vdev)
> > > > break;
> > > > case VIRTIO_F_RING_PACKED:
> > > > break;
> > > > + case VIRTIO_F_ORDER_PLATFORM:
> > > > + break;
> > > > default:
> > > > /* We don't understand this bit. */
> > > > __virtio_clear_bit(vdev, i);
> > > > diff --git a/include/uapi/linux/virtio_config.h
> > > > b/include/uapi/linux/virtio_config.h
> > > > index 1196e1c1d4f6..ff8e7dc9d4dd 100644
> > > > --- a/include/uapi/linux/virtio_config.h
> > > > +++ b/include/uapi/linux/virtio_config.h
> > > > @@ -78,6 +78,12 @@
> > > >/* This feature indicates support for the packed virtqueue layout. */
> > > >#define VIRTIO_F_RING_PACKED 34
> > > > +/*
> > > > + * This feature indicates that memory accesses by the driver and the
> > > > + * device are ordered in a way described by the platform.
> > > > + */
> > > > +#define VIRTIO_F_ORDER_PLATFORM36
> > > > +
> > > >/*
> > > > * Does the device support Single Root I/O Virtualization?
> > > > */
> > >
> > > I wonder whether or not this is sufficient. Is dma barrier implies a mmio
> > > barrier? Looks not.
> > IIUC we don't need an mmio barrier because we are using a
> > serializing API: Documentation/memory-barriers.txt says:
> >
> > Note that, when using writel(), a prior
> > wmb() is not needed to guarantee that the cache coherent memory writes
> > have completed before writing to the MMIO region.
>
>
> Ah, I get this.
>
>
> >
> >
> > > See ia64/include/asm/barrier.h:
> > >
> > > * Note: "mb()" and its variants cannot be used as a fence to order
> > > * accesses to memory mapped I/O registers. For that, mf.a needs to
> > > * be used. However, we don't want to always use mf.a because (a)
> > > * it's (presumably) much slower than mf and (b) mf.a is supported for
> > > * sequential memory pages only.
> > > */
> > > #define mb() ia64_mf()
> > > #define rmb() mb()
> > > #define wmb() mb()
> > >
> > > #define dma_rmb() mb()
> > > =>efine dma_wmb() mb()
> > >
> > > Thanks
> > Frankly no idea about ia64.
>
>
> Neither did me.
>
>
> > Sorry. Are any less esoteric platforms
> > affected?
> >
>
> E.g ppc64?
So
void iowrite32(u32 val, void __iomem *addr)
{
writel(val, addr);
}
and that eventually gets to this one:
#define DEF_MMIO_OUT_D(name, size, insn)\
static inline void name(volatile u##size __iomem *addr, u##size val)\
{ \
__asm__ __volatile__("sync;"#insn"%U0%X0 %1,%0" \
: "=m" (*addr) : "r" (val) : "memory"); \
IO_SET_SYNC_FLAG(); \
}
and
#ifdef CONFIG_PPC64
#define IO_SET_SYNC_FLAG() do { local_paca->io_sync = 1; } while(0)
#else
#define IO_SET_SYNC_FLAG()
#endif
> define
Re: [virtio-dev] [PATCH] virtio: support VIRTIO_F_ORDER_PLATFORM
On 2019/1/23 上午11:49, Michael S. Tsirkin wrote:
On Wed, Jan 23, 2019 at 11:08:04AM +0800, Jason Wang wrote:
On 2019/1/23 上午1:03, Tiwei Bie wrote:
This patch introduces the support for VIRTIO_F_ORDER_PLATFORM.
When this feature is negotiated, driver will use the barriers
suitable for hardware devices.
Signed-off-by: Tiwei Bie
---
drivers/virtio/virtio_ring.c | 8
include/uapi/linux/virtio_config.h | 6 ++
2 files changed, 14 insertions(+)
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index cd7e755484e3..27d3f057493e 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -1609,6 +1609,9 @@ static struct virtqueue *vring_create_virtqueue_packed(
!context;
vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX);
+ if (virtio_has_feature(vdev, VIRTIO_F_ORDER_PLATFORM))
+ vq->weak_barriers = false;
+
vq->packed.ring_dma_addr = ring_dma_addr;
vq->packed.driver_event_dma_addr = driver_event_dma_addr;
vq->packed.device_event_dma_addr = device_event_dma_addr;
@@ -2079,6 +2082,9 @@ struct virtqueue *__vring_new_virtqueue(unsigned int
index,
!context;
vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX);
+ if (virtio_has_feature(vdev, VIRTIO_F_ORDER_PLATFORM))
+ vq->weak_barriers = false;
+
vq->split.queue_dma_addr = 0;
vq->split.queue_size_in_bytes = 0;
@@ -2213,6 +2219,8 @@ void vring_transport_features(struct virtio_device *vdev)
break;
case VIRTIO_F_RING_PACKED:
break;
+ case VIRTIO_F_ORDER_PLATFORM:
+ break;
default:
/* We don't understand this bit. */
__virtio_clear_bit(vdev, i);
diff --git a/include/uapi/linux/virtio_config.h
b/include/uapi/linux/virtio_config.h
index 1196e1c1d4f6..ff8e7dc9d4dd 100644
--- a/include/uapi/linux/virtio_config.h
+++ b/include/uapi/linux/virtio_config.h
@@ -78,6 +78,12 @@
/* This feature indicates support for the packed virtqueue layout. */
#define VIRTIO_F_RING_PACKED 34
+/*
+ * This feature indicates that memory accesses by the driver and the
+ * device are ordered in a way described by the platform.
+ */
+#define VIRTIO_F_ORDER_PLATFORM36
+
/*
* Does the device support Single Root I/O Virtualization?
*/
I wonder whether or not this is sufficient. Is dma barrier implies a mmio
barrier? Looks not.
IIUC we don't need an mmio barrier because we are using a
serializing API: Documentation/memory-barriers.txt says:
Note that, when using writel(), a prior
wmb() is not needed to guarantee that the cache coherent memory writes
have completed before writing to the MMIO region.
Ah, I get this.
See ia64/include/asm/barrier.h:
* Note: "mb()" and its variants cannot be used as a fence to order
* accesses to memory mapped I/O registers. For that, mf.a needs to
* be used. However, we don't want to always use mf.a because (a)
* it's (presumably) much slower than mf and (b) mf.a is supported for
* sequential memory pages only.
*/
#define mb() ia64_mf()
#define rmb() mb()
#define wmb() mb()
#define dma_rmb() mb()
=>efine dma_wmb() mb()
Thanks
Frankly no idea about ia64.
Neither did me.
Sorry. Are any less esoteric platforms
affected?
E.g ppc64?
define dma_wmb() __asm__ __volatile__ (stringify_in_c(SMPWMB) : :
:"memo\
ry")
/*
* Enforce synchronisation of stores vs. spin_unlock
* (this does it explicitly, though our implementation of spin_unlock
* does it implicitely too)
*/
static inline void mmiowb(void)
{
unsigned long tmp;
__asm__ __volatile__("sync; li %0,0; stb %0,%1(13)"
: "=" (tmp) : "i" (offsetof(struct paca_struct, io_sync))
: "memory");
}
dma_wmb() is lwsync which is more lightweight than sync I guess?
Thanks
Re: [virtio-dev] [PATCH] virtio: support VIRTIO_F_ORDER_PLATFORM
On Wed, Jan 23, 2019 at 11:08:04AM +0800, Jason Wang wrote: > > On 2019/1/23 上午1:03, Tiwei Bie wrote: > > This patch introduces the support for VIRTIO_F_ORDER_PLATFORM. > > When this feature is negotiated, driver will use the barriers > > suitable for hardware devices. > > > > Signed-off-by: Tiwei Bie > > --- > > drivers/virtio/virtio_ring.c | 8 > > include/uapi/linux/virtio_config.h | 6 ++ > > 2 files changed, 14 insertions(+) > > > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > > index cd7e755484e3..27d3f057493e 100644 > > --- a/drivers/virtio/virtio_ring.c > > +++ b/drivers/virtio/virtio_ring.c > > @@ -1609,6 +1609,9 @@ static struct virtqueue > > *vring_create_virtqueue_packed( > > !context; > > vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX); > > + if (virtio_has_feature(vdev, VIRTIO_F_ORDER_PLATFORM)) > > + vq->weak_barriers = false; > > + > > vq->packed.ring_dma_addr = ring_dma_addr; > > vq->packed.driver_event_dma_addr = driver_event_dma_addr; > > vq->packed.device_event_dma_addr = device_event_dma_addr; > > @@ -2079,6 +2082,9 @@ struct virtqueue *__vring_new_virtqueue(unsigned int > > index, > > !context; > > vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX); > > + if (virtio_has_feature(vdev, VIRTIO_F_ORDER_PLATFORM)) > > + vq->weak_barriers = false; > > + > > vq->split.queue_dma_addr = 0; > > vq->split.queue_size_in_bytes = 0; > > @@ -2213,6 +2219,8 @@ void vring_transport_features(struct virtio_device > > *vdev) > > break; > > case VIRTIO_F_RING_PACKED: > > break; > > + case VIRTIO_F_ORDER_PLATFORM: > > + break; > > default: > > /* We don't understand this bit. */ > > __virtio_clear_bit(vdev, i); > > diff --git a/include/uapi/linux/virtio_config.h > > b/include/uapi/linux/virtio_config.h > > index 1196e1c1d4f6..ff8e7dc9d4dd 100644 > > --- a/include/uapi/linux/virtio_config.h > > +++ b/include/uapi/linux/virtio_config.h > > @@ -78,6 +78,12 @@ > > /* This feature indicates support for the packed virtqueue layout. */ > > #define VIRTIO_F_RING_PACKED 34 > > +/* > > + * This feature indicates that memory accesses by the driver and the > > + * device are ordered in a way described by the platform. > > + */ > > +#define VIRTIO_F_ORDER_PLATFORM36 > > + > > /* > >* Does the device support Single Root I/O Virtualization? > >*/ > > > I wonder whether or not this is sufficient. Is dma barrier implies a mmio > barrier? Looks not. IIUC we don't need an mmio barrier because we are using a serializing API: Documentation/memory-barriers.txt says: Note that, when using writel(), a prior wmb() is not needed to guarantee that the cache coherent memory writes have completed before writing to the MMIO region. > See ia64/include/asm/barrier.h: > > * Note: "mb()" and its variants cannot be used as a fence to order > * accesses to memory mapped I/O registers. For that, mf.a needs to > * be used. However, we don't want to always use mf.a because (a) > * it's (presumably) much slower than mf and (b) mf.a is supported for > * sequential memory pages only. > */ > #define mb() ia64_mf() > #define rmb() mb() > #define wmb() mb() > > #define dma_rmb() mb() > =>efine dma_wmb() mb() > > Thanks Frankly no idea about ia64. Sorry. Are any less esoteric platforms affected? -- MST
Re: [virtio-dev] [PATCH] virtio: support VIRTIO_F_ORDER_PLATFORM
On 2019/1/23 上午1:03, Tiwei Bie wrote: This patch introduces the support for VIRTIO_F_ORDER_PLATFORM. When this feature is negotiated, driver will use the barriers suitable for hardware devices. Signed-off-by: Tiwei Bie --- drivers/virtio/virtio_ring.c | 8 include/uapi/linux/virtio_config.h | 6 ++ 2 files changed, 14 insertions(+) diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index cd7e755484e3..27d3f057493e 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -1609,6 +1609,9 @@ static struct virtqueue *vring_create_virtqueue_packed( !context; vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX); + if (virtio_has_feature(vdev, VIRTIO_F_ORDER_PLATFORM)) + vq->weak_barriers = false; + vq->packed.ring_dma_addr = ring_dma_addr; vq->packed.driver_event_dma_addr = driver_event_dma_addr; vq->packed.device_event_dma_addr = device_event_dma_addr; @@ -2079,6 +2082,9 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index, !context; vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX); + if (virtio_has_feature(vdev, VIRTIO_F_ORDER_PLATFORM)) + vq->weak_barriers = false; + vq->split.queue_dma_addr = 0; vq->split.queue_size_in_bytes = 0; @@ -2213,6 +2219,8 @@ void vring_transport_features(struct virtio_device *vdev) break; case VIRTIO_F_RING_PACKED: break; + case VIRTIO_F_ORDER_PLATFORM: + break; default: /* We don't understand this bit. */ __virtio_clear_bit(vdev, i); diff --git a/include/uapi/linux/virtio_config.h b/include/uapi/linux/virtio_config.h index 1196e1c1d4f6..ff8e7dc9d4dd 100644 --- a/include/uapi/linux/virtio_config.h +++ b/include/uapi/linux/virtio_config.h @@ -78,6 +78,12 @@ /* This feature indicates support for the packed virtqueue layout. */ #define VIRTIO_F_RING_PACKED 34 +/* + * This feature indicates that memory accesses by the driver and the + * device are ordered in a way described by the platform. + */ +#define VIRTIO_F_ORDER_PLATFORM36 + /* * Does the device support Single Root I/O Virtualization? */ I wonder whether or not this is sufficient. Is dma barrier implies a mmio barrier? Looks not. See ia64/include/asm/barrier.h: * Note: "mb()" and its variants cannot be used as a fence to order * accesses to memory mapped I/O registers. For that, mf.a needs to * be used. However, we don't want to always use mf.a because (a) * it's (presumably) much slower than mf and (b) mf.a is supported for * sequential memory pages only. */ #define mb() ia64_mf() #define rmb() mb() #define wmb() mb() #define dma_rmb() mb() =>efine dma_wmb() mb() Thanks
