search for: smp_wmb

...wrote: > > > This defines __smp_xxx barriers for s390, > > > for use by virtualization. > > > > > > Some smp_xxx barriers are removed as they are > > > defined correctly by asm-generic/barriers.h > > > > > > Note: smp_mb, smp_rmb and smp_wmb are defined as full barriers > > > unconditionally on this architecture. > > > > > > Signed-off-by: Michael S. Tsirkin <mst at redhat.com> > > > Acked-by: Arnd Bergmann <arnd at arndb.de> > > > --- > > > arch/s390/include/asm/barri...

...wrote: > > > This defines __smp_xxx barriers for s390, > > > for use by virtualization. > > > > > > Some smp_xxx barriers are removed as they are > > > defined correctly by asm-generic/barriers.h > > > > > > Note: smp_mb, smp_rmb and smp_wmb are defined as full barriers > > > unconditionally on this architecture. > > > > > > Signed-off-by: Michael S. Tsirkin <mst at redhat.com> > > > Acked-by: Arnd Bergmann <arnd at arndb.de> > > > --- > > > arch/s390/include/asm/barri...

...390, > > > > > for use by virtualization. > > > > > > > > > > Some smp_xxx barriers are removed as they are > > > > > defined correctly by asm-generic/barriers.h > > > > > > > > > > Note: smp_mb, smp_rmb and smp_wmb are defined as full barriers > > > > > unconditionally on this architecture. > > > > > > > > > > Signed-off-by: Michael S. Tsirkin <mst at redhat.com> > > > > > Acked-by: Arnd Bergmann <arnd at arndb.de> > > > > &g...

...390, > > > > > for use by virtualization. > > > > > > > > > > Some smp_xxx barriers are removed as they are > > > > > defined correctly by asm-generic/barriers.h > > > > > > > > > > Note: smp_mb, smp_rmb and smp_wmb are defined as full barriers > > > > > unconditionally on this architecture. > > > > > > > > > > Signed-off-by: Michael S. Tsirkin <mst at redhat.com> > > > > > Acked-by: Arnd Bergmann <arnd at arndb.de> > > > > &g...

Patch 1 removes CONFIG_SMP Patch 2 removes separate smp_{,r,w}mb()s as a result of patch 1 Patch 4 removes __ia64__ defines from the x86 arch tree Patch 3 is related to patch 4 and changes the VIOAPIC to emulate version 0x20 as a performance gain. It preceeds Patch 4 so as to be more clear about the functional change. Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

...fines __smp_xxx barriers for s390, > > > > for use by virtualization. > > > > > > > > Some smp_xxx barriers are removed as they are > > > > defined correctly by asm-generic/barriers.h > > > > > > > > Note: smp_mb, smp_rmb and smp_wmb are defined as full barriers > > > > unconditionally on this architecture. > > > > > > > > Signed-off-by: Michael S. Tsirkin <mst at redhat.com> > > > > Acked-by: Arnd Bergmann <arnd at arndb.de> > > > > --- > > > &gt...

...> for use by virtualization. > > > > > > > > > > > > Some smp_xxx barriers are removed as they are > > > > > > defined correctly by asm-generic/barriers.h > > > > > > > > > > > > Note: smp_mb, smp_rmb and smp_wmb are defined as full barriers > > > > > > unconditionally on this architecture. > > > > > > > > > > > > Signed-off-by: Michael S. Tsirkin <mst at redhat.com> > > > > > > Acked-by: Arnd Bergmann <arnd at arndb.de> &g...

...le now and no bugs were reported there should be something. Actually, we already have an implementation of TSC page update in KVM (see arch/x86/kvm/hyperv.c, kvm_hv_setup_tsc_page()) and the update does the following: 0) stash seq into seq_prev 1) seq = 0 making all reads from the page invalid 2) smp_wmb() 3) update tsc_scale, tsc_offset 4) smp_wmb() 5) set seq = seq_prev + 1 As far as I understand this helps with situations you described above as guest will notice either invalid value of 0 or seq change. In case the implementation in real Hyper-V is the same we're safe with compile barriers o...

...le now and no bugs were reported there should be something. Actually, we already have an implementation of TSC page update in KVM (see arch/x86/kvm/hyperv.c, kvm_hv_setup_tsc_page()) and the update does the following: 0) stash seq into seq_prev 1) seq = 0 making all reads from the page invalid 2) smp_wmb() 3) update tsc_scale, tsc_offset 4) smp_wmb() 5) set seq = seq_prev + 1 As far as I understand this helps with situations you described above as guest will notice either invalid value of 0 or seq change. In case the implementation in real Hyper-V is the same we're safe with compile barriers o...

This change makes it so that instead of using smp_wmb/rmb which varies depending on the kernel configuration we can can use dma_wmb/rmb which for most architectures should be equal to or slightly more strict than smp_wmb/rmb. The advantage to this is that these barriers are available to uniprocessor builds as well so the performance should improve un...

This change makes it so that instead of using smp_wmb/rmb which varies depending on the kernel configuration we can can use dma_wmb/rmb which for most architectures should be equal to or slightly more strict than smp_wmb/rmb. The advantage to this is that these barriers are available to uniprocessor builds as well so the performance should improve un...

...t;> Actually, we already have an implementation of TSC page update in KVM >> (see arch/x86/kvm/hyperv.c, kvm_hv_setup_tsc_page()) and the update does >> the following: >> >> 0) stash seq into seq_prev >> 1) seq = 0 making all reads from the page invalid >> 2) smp_wmb() >> 3) update tsc_scale, tsc_offset >> 4) smp_wmb() >> 5) set seq = seq_prev + 1 > > I hope they handle the case where seq_prev overflows and becomes 0 :) > >> As far as I understand this helps with situations you described above as >> guest will notice eithe...

...t;> Actually, we already have an implementation of TSC page update in KVM >> (see arch/x86/kvm/hyperv.c, kvm_hv_setup_tsc_page()) and the update does >> the following: >> >> 0) stash seq into seq_prev >> 1) seq = 0 making all reads from the page invalid >> 2) smp_wmb() >> 3) update tsc_scale, tsc_offset >> 4) smp_wmb() >> 5) set seq = seq_prev + 1 > > I hope they handle the case where seq_prev overflows and becomes 0 :) > >> As far as I understand this helps with situations you described above as >> guest will notice eithe...

On Thu, Dec 31, 2015 at 09:08:38PM +0200, Michael S. Tsirkin wrote: > This defines __smp_xxx barriers for s390, > for use by virtualization. > > Some smp_xxx barriers are removed as they are > defined correctly by asm-generic/barriers.h > > Note: smp_mb, smp_rmb and smp_wmb are defined as full barriers > unconditionally on this architecture. > > Signed-off-by: Michael S. Tsirkin <mst at redhat.com> > Acked-by: Arnd Bergmann <arnd at arndb.de> > --- > arch/s390/include/asm/barrier.h | 15 +++++++++------ > 1 file changed, 9 insertions...

On Thu, Dec 31, 2015 at 09:08:38PM +0200, Michael S. Tsirkin wrote: > This defines __smp_xxx barriers for s390, > for use by virtualization. > > Some smp_xxx barriers are removed as they are > defined correctly by asm-generic/barriers.h > > Note: smp_mb, smp_rmb and smp_wmb are defined as full barriers > unconditionally on this architecture. > > Signed-off-by: Michael S. Tsirkin <mst at redhat.com> > Acked-by: Arnd Bergmann <arnd at arndb.de> > --- > arch/s390/include/asm/barrier.h | 15 +++++++++------ > 1 file changed, 9 insertions...

...ichael S. Tsirkin wrote: > > arch/s390/kernel/vdso.c: smp_mb(); > > Looking at > Author: Christian Borntraeger <borntraeger at de.ibm.com> > Date: Fri Sep 11 16:23:06 2015 +0200 > > s390/vdso: use correct memory barrier > > By definition smp_wmb only orders writes against writes. (Finish all > previous writes, and do not start any future write). To protect the > vdso init code against early reads on other CPUs, let's use a full > smp_mb at the end of vdso init. As right now smp_wmb is implemented > as fu...

...ichael S. Tsirkin wrote: > > arch/s390/kernel/vdso.c: smp_mb(); > > Looking at > Author: Christian Borntraeger <borntraeger at de.ibm.com> > Date: Fri Sep 11 16:23:06 2015 +0200 > > s390/vdso: use correct memory barrier > > By definition smp_wmb only orders writes against writes. (Finish all > previous writes, and do not start any future write). To protect the > vdso init code against early reads on other CPUs, let's use a full > smp_mb at the end of vdso init. As right now smp_wmb is implemented > as fu...

...ckpatch.pl > index 2b3c228..0245bbe 100755 > --- a/scripts/checkpatch.pl > +++ b/scripts/checkpatch.pl > @@ -5116,7 +5116,14 @@ sub process { > ? } > ? } > ?# check for memory barriers without a comment. > - if ($line =~ /\b(mb|rmb|wmb|read_barrier_depends|smp_mb|smp_rmb|smp_wmb|smp_read_barrier_depends)\(/) { > + > + my @barriers = ('mb', 'rmb', 'wmb', 'read_barrier_depends'); > + my @smp_barriers = ('smp_store_release', 'smp_load_acquire', 'smp_store_mb'); > + > + @smp_barriers = (@smp_barriers, ma...

...ckpatch.pl > index 2b3c228..0245bbe 100755 > --- a/scripts/checkpatch.pl > +++ b/scripts/checkpatch.pl > @@ -5116,7 +5116,14 @@ sub process { > ? } > ? } > ?# check for memory barriers without a comment. > - if ($line =~ /\b(mb|rmb|wmb|read_barrier_depends|smp_mb|smp_rmb|smp_wmb|smp_read_barrier_depends)\(/) { > + > + my @barriers = ('mb', 'rmb', 'wmb', 'read_barrier_depends'); > + my @smp_barriers = ('smp_store_release', 'smp_load_acquire', 'smp_store_mb'); > + > + @smp_barriers = (@smp_barriers, ma...

...this looks a bit confusing. Shouldn't we do if (!node) { schedule(); continue; } just to make the code a bit more clear? If node == NULL then llist_reverse_order() and llist_for_each_entry_safe() will do nothing. But this is minor. /* make sure flag is seen after deletion */ smp_wmb(); llist_for_each_entry_safe(work, work_next, node, node) { clear_bit(VHOST_WORK_QUEUED, &work->flags); I am not sure about smp_wmb + clear_bit. Once we clear VHOST_WORK_QUEUED, vhost_work_queue() can add this work again and change work->node->next. That is why we use _safe, but...