Re: [Xen-devel] [PATCH v2 2/4] xen/x86: Drop unnecessary barriers

At 09:04 -0600 on 18 Aug (1503047077), Jan Beulich wrote: > >>> On 18.08.17 at 16:47, wrote: > > At 01:48 -0600 on 17 Aug (1502934495), Jan Beulich wrote: > >> >>> On 16.08.17 at 18:47, wrote: > >> > On 16/08/17 16:23, Jan Beulich wrote: > >> > On

Re: [Xen-devel] [PATCH v2 2/4] xen/x86: Drop unnecessary barriers

At 15:47 +0100 on 18 Aug (1503071247), Tim Deegan wrote: > At 01:48 -0600 on 17 Aug (1502934495), Jan Beulich wrote: > > >>> On 16.08.17 at 18:47, wrote: > > > atomic_read() is not free to be reordered by the compiler. It is an asm > > > volatile with a volatile memory

Re: [Xen-devel] [PATCH v2 2/4] xen/x86: Drop unnecessary barriers

>>> On 18.08.17 at 16:47, wrote: > At 01:48 -0600 on 17 Aug (1502934495), Jan Beulich wrote: >> >>> On 16.08.17 at 18:47, wrote: >> > On 16/08/17 16:23, Jan Beulich wrote: >> > On 16.08.17 at 13:22, wrote: >> >>> ---

Re: [Xen-devel] [PATCH v2 2/4] xen/x86: Drop unnecessary barriers

At 01:48 -0600 on 17 Aug (1502934495), Jan Beulich wrote: > >>> On 16.08.17 at 18:47, wrote: > > On 16/08/17 16:23, Jan Beulich wrote: > > On 16.08.17 at 13:22, wrote: > >>> --- a/xen/arch/x86/mm/shadow/multi.c > >>> +++

Re: [Xen-devel] [PATCH v2 2/4] xen/x86: Drop unnecessary barriers

At 14:55 +0100 on 18 Aug (1503068128), Tim Deegan wrote: > At 12:22 +0100 on 16 Aug (1502886128), Andrew Cooper wrote: > > diff --git a/xen/arch/x86/mm/shadow/multi.c b/xen/arch/x86/mm/shadow/multi.c > > index c9c2252..1e3dfaf 100644 > > --- a/xen/arch/x86/mm/shadow/multi.c > > +++

Re: [Xen-devel] [PATCH v2 2/4] xen/x86: Drop unnecessary barriers

At 12:22 +0100 on 16 Aug (1502886128), Andrew Cooper wrote: > diff --git a/xen/arch/x86/mm/shadow/multi.c b/xen/arch/x86/mm/shadow/multi.c > index c9c2252..1e3dfaf 100644 > --- a/xen/arch/x86/mm/shadow/multi.c > +++ b/xen/arch/x86/mm/shadow/multi.c > @@ -3112,7 +3112,6 @@ static int

Re: [Xen-devel] [PATCH v2 2/4] xen/x86: Drop unnecessary barriers

>>> On 16.08.17 at 19:03, wrote: > On 16/08/17 17:47, Andrew Cooper wrote: >> On 16/08/17 16:23, Jan Beulich wrote: >> On 16.08.17 at 13:22, wrote: --- a/xen/drivers/passthrough/amd/iommu_init.c +++

Re: [Xen-devel] [PATCH v2 2/4] xen/x86: Drop unnecessary barriers

>>> On 16.08.17 at 18:47, wrote: > On 16/08/17 16:23, Jan Beulich wrote: > On 16.08.17 at 13:22, wrote: >>> --- a/xen/arch/x86/mm/shadow/multi.c >>> +++ b/xen/arch/x86/mm/shadow/multi.c >>> @@ -3112,7 +3112,6 @@ static int

Re: [Xen-devel] [PATCH v2 2/4] xen/x86: Drop unnecessary barriers

On 16/08/17 17:47, Andrew Cooper wrote: > On 16/08/17 16:23, Jan Beulich wrote: > On 16.08.17 at 13:22, wrote: >>> x86's current implementation of wmb() is a compiler barrier. As a result, >>> the >>> only change in this patch is to remove an mfence instruction

Re: [Xen-devel] [PATCH v2 2/4] xen/x86: Drop unnecessary barriers

On 16/08/17 16:23, Jan Beulich wrote: On 16.08.17 at 13:22, wrote: >> x86's current implementation of wmb() is a compiler barrier. As a result, >> the >> only change in this patch is to remove an mfence instruction from >> cpuidle_disable_deep_cstate(). >> >>

Re: [Xen-devel] [PATCH v2 2/4] xen/x86: Drop unnecessary barriers

>>> On 16.08.17 at 13:22, wrote: > x86's current implementation of wmb() is a compiler barrier. As a result, the > only change in this patch is to remove an mfence instruction from > cpuidle_disable_deep_cstate(). > > None of these barriers serve any purpose. Most

[Xen-devel] [PATCH v2 2/4] xen/x86: Drop unnecessary barriers

x86's current implementation of wmb() is a compiler barrier. As a result, the only change in this patch is to remove an mfence instruction from cpuidle_disable_deep_cstate(). None of these barriers serve any purpose. Most aren't aren't synchronising with any remote cpus, where as the mcetelem