similar to: [PATCH v3 02/38] virtio_ring: sparse warning fixup

virtio_store_mb was built with split ring in mind so it accepts __virtio16 arguments. Packed ring uses __le16 values, so sparse complains. It's just a store with some barriers so let's convert it to a macro, we don't loose too much type safety by doing that. Signed-off-by: Michael S. Tsirkin <mst at redhat.com> --- include/linux/virtio_ring.h | 19 +++++++++---------- 1 file

virtio_store_mb was built with split ring in mind so it accepts __virtio16 arguments. Packed ring uses __le16 values, so sparse complains. It's just a store with some barriers so let's convert it to a macro, we don't loose too much type safety by doing that. Signed-off-by: Michael S. Tsirkin <mst at redhat.com> --- include/linux/virtio_ring.h | 19 +++++++++---------- 1 file

We need a full barrier after writing out event index, using virt_store_mb there seems better than open-coding. As usual, we need a wrapper to account for strong barriers. It's tempting to use this in vhost as well, for that, we'll need a variant of smp_store_mb that works on __user pointers. Signed-off-by: Michael S. Tsirkin <mst at redhat.com> --- include/linux/virtio_ring.h |

Hello. On 12/31/2015 10:09 PM, Michael S. Tsirkin wrote: > We need a full barrier after writing out event index, using > virt_store_mb there seems better than open-coding. As usual, we need a > wrapper to account for strong barriers. > > It's tempting to use this in vhost as well, for that, we'll > need a variant of smp_store_mb that works on __user pointers. > >

Hello. On 12/31/2015 10:09 PM, Michael S. Tsirkin wrote: > We need a full barrier after writing out event index, using > virt_store_mb there seems better than open-coding. As usual, we need a > wrapper to account for strong barriers. > > It's tempting to use this in vhost as well, for that, we'll > need a variant of smp_store_mb that works on __user pointers. > >

On Thu, Dec 17, 2015 at 12:22:22PM +0100, Peter Zijlstra wrote: > On Thu, Dec 17, 2015 at 12:32:53PM +0200, Michael S. Tsirkin wrote: > > Seems to give a speedup on my box but I'm less sure about this one. E.g. as > > xchng faster than mfence on all/most intel CPUs? Anyone has an opinion? > > Would help if you Cc people who would actually know this :-) Good point. Glad

On Thu, Dec 17, 2015 at 12:22:22PM +0100, Peter Zijlstra wrote: > On Thu, Dec 17, 2015 at 12:32:53PM +0200, Michael S. Tsirkin wrote: > > Seems to give a speedup on my box but I'm less sure about this one. E.g. as > > xchng faster than mfence on all/most intel CPUs? Anyone has an opinion? > > Would help if you Cc people who would actually know this :-) Good point. Glad

We need a full barrier after writing out event index, using smp_store_mb there seems better than open-coding. As usual, we need a wrapper to account for strong barriers/non smp. It's tempting to use this in vhost as well, for that, we'll need a variant of smp_store_mb that works on __user pointers. Signed-off-by: Michael S. Tsirkin <mst at redhat.com> --- Seems to give a speedup

We need a full barrier after writing out event index, using smp_store_mb there seems better than open-coding. As usual, we need a wrapper to account for strong barriers/non smp. It's tempting to use this in vhost as well, for that, we'll need a variant of smp_store_mb that works on __user pointers. Signed-off-by: Michael S. Tsirkin <mst at redhat.com> --- Seems to give a speedup

virtio is using barriers to order memory accesses, thus dma_wmb/rmb is a good match. Build-tested on x86: Before [mst at tuck linux]$ size drivers/virtio/virtio_ring.o text data bss dec hex filename 11392 820 0 12212 2fb4 drivers/virtio/virtio_ring.o After mst at tuck linux]$ size drivers/virtio/virtio_ring.o text data bss dec hex filename

virtio is using barriers to order memory accesses, thus dma_wmb/rmb is a good match. Build-tested on x86: Before [mst at tuck linux]$ size drivers/virtio/virtio_ring.o text data bss dec hex filename 11392 820 0 12212 2fb4 drivers/virtio/virtio_ring.o After mst at tuck linux]$ size drivers/virtio/virtio_ring.o text data bss dec hex filename

On 19/04/2018 19:35, Michael S. Tsirkin wrote: > virtio is using barriers to order memory accesses, thus > dma_wmb/rmb is a good match. > > Build-tested on x86: Before > > [mst at tuck linux]$ size drivers/virtio/virtio_ring.o > text data bss dec hex filename > 11392 820 0 12212 2fb4 drivers/virtio/virtio_ring.o > > After > mst

On Thu, Dec 17, 2015 at 11:52:38AM +0100, Peter Zijlstra wrote: > On Thu, Dec 17, 2015 at 12:32:53PM +0200, Michael S. Tsirkin wrote: > > +static inline void virtio_store_mb(bool weak_barriers, > > + __virtio16 *p, __virtio16 v) > > +{ > > +#ifdef CONFIG_SMP > > + if (weak_barriers) > > + smp_store_mb(*p, v); > > + else > > +#endif >

On Thu, Dec 17, 2015 at 11:52:38AM +0100, Peter Zijlstra wrote: > On Thu, Dec 17, 2015 at 12:32:53PM +0200, Michael S. Tsirkin wrote: > > +static inline void virtio_store_mb(bool weak_barriers, > > + __virtio16 *p, __virtio16 v) > > +{ > > +#ifdef CONFIG_SMP > > + if (weak_barriers) > > + smp_store_mb(*p, v); > > + else > > +#endif >

On Thu, Apr 19, 2018 at 07:39:21PM +0200, Paolo Bonzini wrote: > On 19/04/2018 19:35, Michael S. Tsirkin wrote: > > virtio is using barriers to order memory accesses, thus > > dma_wmb/rmb is a good match. > > > > Build-tested on x86: Before > > > > [mst at tuck linux]$ size drivers/virtio/virtio_ring.o > > text data bss dec hex

On Thu, Apr 19, 2018 at 07:39:21PM +0200, Paolo Bonzini wrote: > On 19/04/2018 19:35, Michael S. Tsirkin wrote: > > virtio is using barriers to order memory accesses, thus > > dma_wmb/rmb is a good match. > > > > Build-tested on x86: Before > > > > [mst at tuck linux]$ size drivers/virtio/virtio_ring.o > > text data bss dec hex

On Thu, Dec 17, 2015 at 02:57:26PM +0100, Peter Zijlstra wrote: > On Thu, Dec 17, 2015 at 03:16:20PM +0200, Michael S. Tsirkin wrote: > > On Thu, Dec 17, 2015 at 11:52:38AM +0100, Peter Zijlstra wrote: > > > On Thu, Dec 17, 2015 at 12:32:53PM +0200, Michael S. Tsirkin wrote: > > > > +static inline void virtio_store_mb(bool weak_barriers, > > > > +

On Thu, Dec 17, 2015 at 02:57:26PM +0100, Peter Zijlstra wrote: > On Thu, Dec 17, 2015 at 03:16:20PM +0200, Michael S. Tsirkin wrote: > > On Thu, Dec 17, 2015 at 11:52:38AM +0100, Peter Zijlstra wrote: > > > On Thu, Dec 17, 2015 at 12:32:53PM +0200, Michael S. Tsirkin wrote: > > > > +static inline void virtio_store_mb(bool weak_barriers, > > > > +

On Thu, Dec 17, 2015 at 03:16:20PM +0200, Michael S. Tsirkin wrote: > On Thu, Dec 17, 2015 at 11:52:38AM +0100, Peter Zijlstra wrote: > > On Thu, Dec 17, 2015 at 12:32:53PM +0200, Michael S. Tsirkin wrote: > > > +static inline void virtio_store_mb(bool weak_barriers, > > > + __virtio16 *p, __virtio16 v) > > > +{ > > > +#ifdef CONFIG_SMP > >

On Tue, Apr 07, 2015 at 05:47:42PM -0700, Alexander Duyck wrote: > 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