From: Ben Gardon Date: Tue, 2 Feb 2021 18:57:22 +0000 (-0800) Subject: KVM: x86/mmu: Clear dirtied pages mask bit before early break X-Git-Tag: v5.15~1543^2~141 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=f1b3b06a058bb5c636ffad0afae138fe30775881;p=platform%2Fkernel%2Flinux-starfive.git KVM: x86/mmu: Clear dirtied pages mask bit before early break In clear_dirty_pt_masked, the loop is intended to exit early after processing each of the GFNs with corresponding bits set in mask. This does not work as intended if another thread has already cleared the dirty bit or writable bit on the SPTE. In that case, the loop would proceed to the next iteration early and the bit in mask would not be cleared. As a result the loop could not exit early and would proceed uselessly. Move the unsetting of the mask bit before the check for a no-op SPTE change. Fixes: a6a0b05da9f3 ("kvm: x86/mmu: Support dirty logging for the TDP MMU") Suggested-by: Sean Christopherson Signed-off-by: Ben Gardon Message-Id: <20210202185734.1680553-17-bgardon@google.com> Signed-off-by: Paolo Bonzini --- diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index aeb05f6..a75e921 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -1007,6 +1007,8 @@ static void clear_dirty_pt_masked(struct kvm *kvm, struct kvm_mmu_page *root, !(mask & (1UL << (iter.gfn - gfn)))) continue; + mask &= ~(1UL << (iter.gfn - gfn)); + if (wrprot || spte_ad_need_write_protect(iter.old_spte)) { if (is_writable_pte(iter.old_spte)) new_spte = iter.old_spte & ~PT_WRITABLE_MASK; @@ -1020,8 +1022,6 @@ static void clear_dirty_pt_masked(struct kvm *kvm, struct kvm_mmu_page *root, } tdp_mmu_set_spte_no_dirty_log(kvm, &iter, new_spte); - - mask &= ~(1UL << (iter.gfn - gfn)); } }