[PATCH 0/7] KVM/X86/PPC: Clear up kvm mmu memory barriers and update related comments

[PATCH 0/7] KVM/X86/PPC: Clear up kvm mmu memory barriers and update related comments

[Lan Tianyu]

This series is to clear up kvm mmu memory barriers.
1) Remove redundant barrier (PATCH 1)
2) Replace origin barrier functions with preferrable ones (PATCH 2, 3, 5)
3) Fix unpaired barriers (PATCH 4)
4) Update or add barrier related comments (PATCH 6, 7)

Lan Tianyu (7):
  KVM: Remove redundant smp_mb() in the kvm_mmu_commit_zap_page()
  KVM/x86: Replace smp_mb() with smp_store_mb/release() in the
    walk_shadow_page_lockless_begin/end()
  KVM: Replace smp_mb() with smp_mb_after_atomic() in the
    kvm_make_all_cpus_request()
  KVM/x86: Call smp_wmb() before increasing tlbs_dirty
  KVM: Replace smp_mb() with smp_load_acquire() in the
    kvm_flush_remote_tlbs()
  KVM/x86: update the comment of memory barrier in the
    vcpu_enter_guest()
  KVM/PPC:  update the comment of memory barrier in the
    kvmppc_prepare_to_enter()

 arch/powerpc/kvm/powerpc.c |  3 +++
 arch/x86/kvm/mmu.c         | 23 ++++++++++-------------
 arch/x86/kvm/paging_tmpl.h | 11 +++++++++++
 arch/x86/kvm/x86.c         |  8 ++++++--
 virt/kvm/kvm_main.c        | 22 ++++++++++++++++++----
 5 files changed, 48 insertions(+), 19 deletions(-)

-- 
1.8.4.rc0.1.g8f6a3e5.dirty

[PATCH 7/7] KVM/PPC: update the comment of memory barrier in the kvmppc_prepare_to_enter()

[Lan Tianyu]

The barrier also orders the write to mode from any reads
to the page tables done and so update the comment.

Signed-off-by: Lan Tianyu <tianyu.lan@intel.com>
---
 arch/powerpc/kvm/powerpc.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 19aa59b..6a68730 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -96,6 +96,9 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu)
 		 * so we don't miss a request because the requester sees
 		 * OUTSIDE_GUEST_MODE and assumes we'll be checking requests
 		 * before next entering the guest (and thus doesn't IPI).
+		 * This also orders the write to mode from any reads
+		 * to the page tables done while the VCPU is running.
+		 * Please see the comment in kvm_flush_remote_tlbs.
 		 */
 		smp_mb();
 
-- 
1.8.4.rc0.1.g8f6a3e5.dirty

Re: [PATCH 0/7] KVM/X86/PPC: Clear up kvm mmu memory barriers and update related comments

[Paolo Bonzini]

On 13/03/2016 04:10, Lan Tianyu wrote:
> This series is to clear up kvm mmu memory barriers.
> 1) Remove redundant barrier (PATCH 1)
> 2) Replace origin barrier functions with preferrable ones (PATCH 2, 3, 5)
> 3) Fix unpaired barriers (PATCH 4)
> 4) Update or add barrier related comments (PATCH 6, 7)

Thanks, this looks pretty good!  I will apply it for 4.6 if I have to
send two pull requests during this merge window; otherwise, it will have
to wait for the next merge window.

Paolo