search for: smp_xx

Documentation/memory-barriers.txt says: Mandatory barriers should not be used to control SMP effects, since mandatory barriers unnecessarily impose overhead on UP systems. This rule applies to virtio, so let's do it correctly. Signed-off-by: Michael S. Tsirkin <mst at redhat.com> --- drivers/virtio/virtio_ring.c | 12 ++++++------ 1 files changed, 6 insertions(+), 6 deletions(-)

Documentation/memory-barriers.txt says: Mandatory barriers should not be used to control SMP effects, since mandatory barriers unnecessarily impose overhead on UP systems. This rule applies to virtio, so let's do it correctly. Signed-off-by: Michael S. Tsirkin <mst at redhat.com> --- drivers/virtio/virtio_ring.c | 12 ++++++------ 1 files changed, 6 insertions(+), 6 deletions(-)

virtio is communicating with a virtual "device" that actually runs on another host processor. Thus SMP barriers can be used to control memory access ordering. Where possible, we should use SMP barriers which are more lightweight than mandatory barriers, because mandatory barriers also control MMIO effects on accesses through relaxed memory I/O windows (which virtio does not use)

virtio is communicating with a virtual "device" that actually runs on another host processor. Thus SMP barriers can be used to control memory access ordering. Where possible, we should use SMP barriers which are more lightweight than mandatory barriers, because mandatory barriers also control MMIO effects on accesses through relaxed memory I/O windows (which virtio does not use)

vhost-net only uses memory barriers to control SMP effects (communication with userspace potentially running on a different CPU), so it should use SMP barriers and not mandatory barriers for memory access ordering, as suggested by Documentation/memory-barriers.txt Signed-off-by: Michael S. Tsirkin <mst at redhat.com> --- drivers/vhost/vhost.c | 10 +++++----- 1 files changed, 5

vhost-net only uses memory barriers to control SMP effects (communication with userspace potentially running on a different CPU), so it should use SMP barriers and not mandatory barriers for memory access ordering, as suggested by Documentation/memory-barriers.txt Signed-off-by: Michael S. Tsirkin <mst at redhat.com> --- drivers/vhost/vhost.c | 10 +++++----- 1 files changed, 5

...) processors, each of which might either be UP or SMP. To control the ordering of memory references when the vrings are shared between two external processors, we must always use mandatory barriers. A trivial, albeit sub-optimal, solution would be to simply revert commit d57ed95 "virtio: use smp_XX barriers on SMP". Obviously, though, that's going to have a negative impact on performance of SMP-based virtualization use cases. A different approach, as demonstrated by this patch, would pick the type of memory barriers, in run time, according to the requirements of the virtio device. T...

...) processors, each of which might either be UP or SMP. To control the ordering of memory references when the vrings are shared between two external processors, we must always use mandatory barriers. A trivial, albeit sub-optimal, solution would be to simply revert commit d57ed95 "virtio: use smp_XX barriers on SMP". Obviously, though, that's going to have a negative impact on performance of SMP-based virtualization use cases. A different approach, as demonstrated by this patch, would pick the type of memory barriers, in run time, according to the requirements of the virtio device. T...

...virtio: console: Fill ports' entire in_vq with buffers Add MAINTAINERS entry for virtio_console Christoph Hellwig (1): virtio_blk: add block topology support Jamie Lokier (1): Add __devexit_p around reference to virtio_pci_remove Michael S. Tsirkin (1): virtio: use smp_XX barriers on SMP Rusty Russell (9): virtio: fix balloon without VIRTIO_BALLOON_F_STATS_VQ lguest: remove unneeded zlib.h include in example launcher virtio: remove bogus barriers from DEBUG version of virtio_ring.c virtio: console: comment cleanup virtio: console: stat...

...virtio: console: Fill ports' entire in_vq with buffers Add MAINTAINERS entry for virtio_console Christoph Hellwig (1): virtio_blk: add block topology support Jamie Lokier (1): Add __devexit_p around reference to virtio_pci_remove Michael S. Tsirkin (1): virtio: use smp_XX barriers on SMP Rusty Russell (9): virtio: fix balloon without VIRTIO_BALLOON_F_STATS_VQ lguest: remove unneeded zlib.h include in example launcher virtio: remove bogus barriers from DEBUG version of virtio_ring.c virtio: console: comment cleanup virtio: console: stat...

...pu(vqconfig[i].used_address)) { > + dev_warn(mic_dev(mvdev), "used_address zero??\n"); > + continue; > + } > + mvdev->vring[i].vr.used = > + mvdev->mdev->aper.va + > + le64_to_cpu(vqconfig[i].used_address); > + } > + > + smp_wmb(); Looking at smp_XX macros, here and elsewhere this driver only has smp_wmb. This seems to violate SMP barrier pairing rules in Documentation/memory-barriers.txt > + mvdev->dc->used_address_updated = 0; > + > + dev_info(mic_dev(mvdev), "%s: device type %d LINKUP\n", > + __func__, mvdev-&...

An Intel MIC X100 device is a PCIe form factor add-in coprocessor card based on the Intel Many Integrated Core (MIC) architecture that runs a Linux OS. It is a PCIe endpoint in a platform and therefore implements the three required standard address spaces i.e. configuration, memory and I/O. The host OS loads a device driver as is typical for PCIe devices. The card itself runs a bootstrap after

An Intel MIC X100 device is a PCIe form factor add-in coprocessor card based on the Intel Many Integrated Core (MIC) architecture that runs a Linux OS. It is a PCIe endpoint in a platform and therefore implements the three required standard address spaces i.e. configuration, memory and I/O. The host OS loads a device driver as is typical for PCIe devices. The card itself runs a bootstrap after