On Thu, 25 Apr 2019, David Laight wrote: > From: Thomas Gleixne] > > Sent: 25 April 2019 11:59 > > On Thu, 25 Apr 2019, David Laight wrote: > > > > > From: Fenghua Yu > > > > Sent: 24 April 2019 20:33 > > > > A split locked access locks bus and degrades overall memory access > > > > performance. When split lock detection feature is enumerated, enable > > > > the feature by default by writing 1 to bit 29 in MSR TEST_CTL to find > > > > any split lock issue. > > > > > > You can't enable this by default until ALL the known potentially > > > misaligned locked memory operations have been fixed. > > > > Errm? The result will be a WARN_ON() printed and no further damage. > > ISTR something about sending SIGSEGV to userspace. Nope. If the #AC originates from kernel then a warning is printed and the detection is disabled. Userspace is a different story. We cannot audit all user space upfront, right? > > It's not making anything worse than it is now. In fact we just should add a > > > > WARN_ON_ONCE(!aligned_to_long(p)) to all the xxx_bit() operations. > > > > so we catch them even when they do not trigger that #AC thingy. > > That will explode the kernel code size. So what? We have enough debug options which make the kernel big. One more does not really matter. Thanks, tglx
