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author | Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp> | 2012-05-09 16:10:39 +0300 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-05-12 09:32:19 -0700 |
commit | 87a6c3e2b97b6556a7184a198d7b862b101c24cd (patch) | |
tree | 9dcec2e712135f5489aca2364199deed7f0a8dcd /virt/kvm | |
parent | f6a0ce750df3fd54adbdbfbaf9f0736763f4f7ac (diff) |
KVM: Fix write protection race during dirty logging
(cherry picked from commit 6dbf79e7164e9a86c1e466062c48498142ae6128)
This patch fixes a race introduced by:
commit 95d4c16ce78cb6b7549a09159c409d52ddd18dae
KVM: Optimize dirty logging by rmap_write_protect()
During protecting pages for dirty logging, other threads may also try
to protect a page in mmu_sync_children() or kvm_mmu_get_page().
In such a case, because get_dirty_log releases mmu_lock before flushing
TLB's, the following race condition can happen:
A (get_dirty_log) B (another thread)
lock(mmu_lock)
clear pte.w
unlock(mmu_lock)
lock(mmu_lock)
pte.w is already cleared
unlock(mmu_lock)
skip TLB flush
return
...
TLB flush
Though thread B assumes the page has already been protected when it
returns, the remaining TLB entry will break that assumption.
This patch fixes this problem by making get_dirty_log hold the mmu_lock
until it flushes the TLB's.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'virt/kvm')
0 files changed, 0 insertions, 0 deletions