From: Takuya Yoshikawa Date: Sun, 5 Feb 2012 11:42:41 +0000 (+0900) Subject: KVM: Fix write protection race during dirty logging X-Git-Tag: v3.4-rc1~59^2~30 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6dbf79e7164e9a86c1e466062c48498142ae6128;p=pandora-kernel.git KVM: Fix write protection race during dirty logging 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 Signed-off-by: Marcelo Tosatti Signed-off-by: Avi Kivity --- Reading git-diff-tree failed