search for: virt_store_mb

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. > > Signed-off-by: Michael S. Tsirkin <mst...

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. > > Signed-off-by: Michael S. Tsirkin <mst...

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> --- incl...

....b485b13fa50b 100644 --- a/include/linux/virtio_ring.h +++ b/include/linux/virtio_ring.h @@ -46,16 +46,15 @@ static inline void virtio_wmb(bool weak_barriers) dma_wmb(); } -static inline void virtio_store_mb(bool weak_barriers, - __virtio16 *p, __virtio16 v) -{ - if (weak_barriers) { - virt_store_mb(*p, v); - } else { - WRITE_ONCE(*p, v); - mb(); - } -} +#define virtio_store_mb(weak_barriers, p, v) \ +do { \ + if (weak_barriers) { \ + virt_store_mb(*p, v); \ + } else { \ + WRITE_ONCE(*p, v); \ + mb(); \ + } \ +} while (0) \ struct virtio_device; struct virtqueue; -- MST

....b485b13fa50b 100644 --- a/include/linux/virtio_ring.h +++ b/include/linux/virtio_ring.h @@ -46,16 +46,15 @@ static inline void virtio_wmb(bool weak_barriers) dma_wmb(); } -static inline void virtio_store_mb(bool weak_barriers, - __virtio16 *p, __virtio16 v) -{ - if (weak_barriers) { - virt_store_mb(*p, v); - } else { - WRITE_ONCE(*p, v); - mb(); - } -} +#define virtio_store_mb(weak_barriers, p, v) \ +do { \ + if (weak_barriers) { \ + virt_store_mb(*p, v); \ + } else { \ + WRITE_ONCE(*p, v); \ + mb(); \ + } \ +} while (0) \ struct virtio_device; struct virtqueue; -- MST

....b485b13fa50b 100644 --- a/include/linux/virtio_ring.h +++ b/include/linux/virtio_ring.h @@ -46,16 +46,15 @@ static inline void virtio_wmb(bool weak_barriers) dma_wmb(); } -static inline void virtio_store_mb(bool weak_barriers, - __virtio16 *p, __virtio16 v) -{ - if (weak_barriers) { - virt_store_mb(*p, v); - } else { - WRITE_ONCE(*p, v); - mb(); - } -} +#define virtio_store_mb(weak_barriers, p, v) \ +do { \ + if (weak_barriers) { \ + virt_store_mb(*p, v); \ + } else { \ + WRITE_ONCE(*p, v); \ + mb(); \ + } \ +} while (0) \ struct virtio_device; struct virtqueue; -- MST

...xx asm-generic: implement virt_xxx memory barriers Revert "virtio_ring: Update weak barriers to use dma_wmb/rmb" virtio_ring: update weak barriers to use virt_xxx sh: support 1 and 2 byte xchg sh: move xchg_cmpxchg to a header by itself virtio_ring: use virt_store_mb xenbus: use virt_xxx barriers xen/io: use virt_xxx barriers xen/events: use virt_xxx barriers s390: use generic memory barriers s390: more efficient smp barriers checkpatch.pl: add missing memory barriers checkpatch: check for __smp outside barrier.h...

...xx asm-generic: implement virt_xxx memory barriers Revert "virtio_ring: Update weak barriers to use dma_wmb/rmb" virtio_ring: update weak barriers to use virt_xxx sh: support 1 and 2 byte xchg sh: move xchg_cmpxchg to a header by itself virtio_ring: use virt_store_mb xenbus: use virt_xxx barriers xen/io: use virt_xxx barriers xen/events: use virt_xxx barriers s390: use generic memory barriers s390: more efficient smp barriers checkpatch.pl: add missing memory barriers checkpatch: check for __smp outside barrier.h...

...dma_rmb() barrier() -# define dma_wmb() barrier() -# define smp_rmb() barrier() -# define smp_wmb() barrier() +#define virt_mb() __sync_synchronize() +#define virt_rmb() barrier() +#define virt_wmb() barrier() +/* Atomic store should be enough, but gcc generates worse code in that case. */ +#define virt_store_mb(var, value) do { \ + typeof(var) virt_store_mb_value = (value); \ + __atomic_exchange(&(var), &virt_store_mb_value, &virt_store_mb_value, \ + __ATOMIC_SEQ_CST); \ + barrier(); \ +} while (0); /* Weak barriers should be used. If not - it's a bug */ -# define rmb() abort() -# de...

...dma_rmb() barrier() -# define dma_wmb() barrier() -# define smp_rmb() barrier() -# define smp_wmb() barrier() +#define virt_mb() __sync_synchronize() +#define virt_rmb() barrier() +#define virt_wmb() barrier() +/* Atomic store should be enough, but gcc generates worse code in that case. */ +#define virt_store_mb(var, value) do { \ + typeof(var) virt_store_mb_value = (value); \ + __atomic_exchange(&(var), &virt_store_mb_value, &virt_store_mb_value, \ + __ATOMIC_SEQ_CST); \ + barrier(); \ +} while (0); /* Weak barriers should be used. If not - it's a bug */ -# define rmb() abort() -# de...

...lement virt_xxx memory barriers > Revert "virtio_ring: Update weak barriers to use dma_wmb/rmb" > virtio_ring: update weak barriers to use virt_xxx > sh: support 1 and 2 byte xchg > sh: move xchg_cmpxchg to a header by itself > virtio_ring: use virt_store_mb > xenbus: use virt_xxx barriers > xen/io: use virt_xxx barriers > xen/events: use virt_xxx barriers > s390: use generic memory barriers > s390: more efficient smp barriers > checkpatch.pl: add missing memory barriers > checkpatch: check...

...or __smp_, and documents them. After all this work, this requires very few lines of code in the generic header. -. Patches 29,30,33,34 convert virtio xen drivers to use the virt_xxx APIs xen patches are untested virtio ones have been tested on x86 -. Patches 31-32 teach virtio to use virt_store_mb sh architecture was missing a 2-byte smp_store_mb, the fix is trivial although my code is not optimal: if anyone cares, pls send me a patch to apply on top. I didn't build this architecture, but intel's 0-day infrastructure builds it. tested on x86 Davidlohr Bueso (1):...

...or __smp_, and documents them. After all this work, this requires very few lines of code in the generic header. -. Patches 29,30,33,34 convert virtio xen drivers to use the virt_xxx APIs xen patches are untested virtio ones have been tested on x86 -. Patches 31-32 teach virtio to use virt_store_mb sh architecture was missing a 2-byte smp_store_mb, the fix is trivial although my code is not optimal: if anyone cares, pls send me a patch to apply on top. I didn't build this architecture, but intel's 0-day infrastructure builds it. tested on x86 Davidlohr Bueso (1):...

...xxx APIs to work for virt: -. Patch 28 adds virt_ wrappers for __smp_, and documents them. After all this work, this requires very few lines of code in the generic header. -. Patches 29,30 convert virtio drivers to use the virt_xxx APIs tested on x86 -. Patches 31-33 teach virtio to use virt_store_mb sh architecture was missing a 2-byte xchg, needed for 2 byte smp_store_mb, so I had to add this support for sh -. Patches 34-36 teach checkpatch to warn about misuse of the new barriers -. Patches 37-39 convert xen drivers to use the virt_xxx APIs compiled only (by intel 0-day infr...

...xxx APIs to work for virt: -. Patch 28 adds virt_ wrappers for __smp_, and documents them. After all this work, this requires very few lines of code in the generic header. -. Patches 29,30 convert virtio drivers to use the virt_xxx APIs tested on x86 -. Patches 31-33 teach virtio to use virt_store_mb sh architecture was missing a 2-byte xchg, needed for 2 byte smp_store_mb, so I had to add this support for sh -. Patches 34-36 teach checkpatch to warn about misuse of the new barriers -. Patches 37-39 convert xen drivers to use the virt_xxx APIs compiled only (by intel 0-day infr...

Config space endian-ness is currently a mess: fields are not tagged with the correct endian-ness so it's easy to make mistakes like instanciating config space in native endian-ness. The following patches adding sparse tagging are currently in my tree. Lightly tested. As a follow-up, I plan to add new APIs that handle modern config space in a more efficient way (bypassing the version check).

Hi all, Although [smp_]read_barrier_depends() became part of READ_ONCE() in commit 76ebbe78f739 ("locking/barriers: Add implicit smp_read_barrier_depends() to READ_ONCE()"), it still limps on in the Linux memory model with the sinister hope of attracting innocent new users so that it becomes impossible to remove altogether. Let's strike before it's too late: there's only

Hi all, This is version three of the patches I previously posted here: v1: https://lore.kernel.org/lkml/20191108170120.22331-1-will at kernel.org/ v2: https://lore.kernel.org/r/20200630173734.14057-1-will at kernel.org Changes since v2 include: * Actually add the barrier in READ_ONCE() for Alpha! * Implement Alpha's smp_load_acquire() using __READ_ONCE(), rather than the other

Hi everyone, This is the long-awaited version two of the patches I previously posted in November last year: https://lore.kernel.org/lkml/20191108170120.22331-1-will at kernel.org/ I ended up parking the series while the READ_ONCE() implementation was being overhauled, but with that merged during the recent merge window and LTO patches being posted again [1], it was time for a refresh. The

Hi everyone, This is the long-awaited version two of the patches I previously posted in November last year: https://lore.kernel.org/lkml/20191108170120.22331-1-will at kernel.org/ I ended up parking the series while the READ_ONCE() implementation was being overhauled, but with that merged during the recent merge window and LTO patches being posted again [1], it was time for a refresh. The