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  1. 28 11月, 2014 2 次提交
  3. 07 11月, 2014 3 次提交
    • H
      KVM: s390: fix handling of lctl[g]/stctl[g] · fc56eb66
      由 Heiko Carstens 提交于 
      According to the architecture all instructions are suppressing if memory
access is prohibited due to DAT protection, unless stated otherwise for
an instruction.
The lctl[g]/stctl[g] implementations handled this incorrectly since
control register handling was done piecemeal, which means they had
terminating instead of suppressing semantics.
This patch fixes this.
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Reviewed-by: NThomas Huth <thuth@linux.vnet.ibm.com>
Reviewed-by: NDavid Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>
      fc56eb66
    • C
      KVM: s390: flush CPU on load control · 2dca485f
      由 Christian Borntraeger 提交于 
      some control register changes will flush some aspects of the CPU, e.g.
POP explicitely mentions that for CR9-CR11 "TLBs may be cleared".
Instead of trying to be clever and only flush on specific CRs, let
play safe and flush on all lctl(g) as future machines might define
new bits in CRs. Load control intercept should not happen that often.
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>
Acked-by: NCornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: NDavid Hildenbrand <dahi@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org
      2dca485f
    • C
      KVM: s390: Fix ipte locking · 1365039d
      由 Christian Borntraeger 提交于 
      ipte_unlock_siif uses cmpxchg to replace the in-memory data of the ipte
lock together with ACCESS_ONCE for the intial read.

union ipte_control {
        unsigned long val;
        struct {
                unsigned long k  : 1;
                unsigned long kh : 31;
                unsigned long kg : 32;
        };
};
[...]
static void ipte_unlock_siif(struct kvm_vcpu *vcpu)
{
        union ipte_control old, new, *ic;

        ic = &vcpu->kvm->arch.sca->ipte_control;
        do {
                new = old = ACCESS_ONCE(*ic);
                new.kh--;
                if (!new.kh)
                        new.k = 0;
        } while (cmpxchg(&ic->val, old.val, new.val) != old.val);
        if (!new.kh)
                wake_up(&vcpu->kvm->arch.ipte_wq);
}

The new value, is loaded twice from memory with gcc 4.7.2 of
fedora 18, despite the ACCESS_ONCE:

--->

l       %r4,0(%r3)      <--- load first 32 bit of lock (k and kh) in r4
alfi    %r4,2147483647  <--- add -1 to r4
llgtr   %r4,%r4         <--- zero out the sign bit of r4
lg      %r1,0(%r3)      <--- load all 64 bit of lock into new
lgr     %r2,%r1         <--- load the same into old
risbg   %r1,%r4,1,31,32 <--- shift and insert r4 into the bits 1-31 of
new
llihf   %r4,2147483647
ngrk    %r4,%r1,%r4
jne     aa0 <ipte_unlock+0xf8>
nihh    %r1,32767
lgr     %r4,%r2
csg     %r4,%r1,0(%r3)
cgr     %r2,%r4
jne     a70 <ipte_unlock+0xc8>

If the memory value changes between the first load (l) and the second
load (lg) we are broken. If that happens VCPU threads will hang
(unkillable) in handle_ipte_interlock.

Andreas Krebbel analyzed this and tracked it down to a compiler bug in
that version:
"while it is not that obvious the C99 standard basically forbids
duplicating the memory access also in that case. For an argumentation of
a similiar case please see:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=22278#c43

For the implementation-defined cases regarding volatile there are some
GCC-specific clarifications which can be found here:
https://gcc.gnu.org/onlinedocs/gcc/Volatiles.html#Volatiles

I've tracked down the problem with a reduced testcase. The problem was
that during a tree level optimization (SRA - scalar replacement of
aggregates) the volatile marker is lost. And an RTL level optimizer (CSE
- common subexpression elimination) then propagated the memory read into
  its second use introducing another access to the memory location. So
indeed Christian's suspicion that the union access has something to do
with it is correct (since it triggered the SRA optimization).

This issue has been reported and fixed in the GCC 4.8 development cycle:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145"

This patch replaces the ACCESS_ONCE scheme with a barrier() based scheme
that should work for all supported compilers.
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>
Cc: stable@vger.kernel.org # v3.16+
      1365039d
  5. 28 10月, 2014 10 次提交
  7. 17 10月, 2014 2 次提交
  9. 15 10月, 2014 1 次提交
  11. 10 10月, 2014 1 次提交
  13. 09 10月, 2014 8 次提交
  15. 03 10月, 2014 1 次提交
  17. 01 10月, 2014 2 次提交
  19. 30 9月, 2014 1 次提交
  21. 26 9月, 2014 2 次提交
  23. 25 9月, 2014 7 次提交