FAILED: patch "[PATCH] kvm: check tlbs_dirty directly" failed to apply to 4.4-stable tree

The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 88bf56d04bc3564542049ec4ec168a8b60d0b48c Mon Sep 17 00:00:00 2001
From: Lai Jiangshan <[email protected]>
Date: Thu, 17 Dec 2020 23:41:18 +0800
Subject: [PATCH] kvm: check tlbs_dirty directly

In kvm_mmu_notifier_invalidate_range_start(), tlbs_dirty is used as:

        need_tlb_flush |= kvm->tlbs_dirty;

with need_tlb_flush's type being int and tlbs_dirty's type being long.

It means that tlbs_dirty is always used as int and the higher 32 bits is useless. We need to check tlbs_dirty in a correct way and this change checks it directly without propagating it to need_tlb_flush.

Note: it's _extremely_ unlikely this neglecting of higher 32 bits can cause problems in practice. It would require encountering tlbs_dirty on a 4 billion count boundary, and KVM would need to be using shadow paging or be running a nested guest.

Message-Id: <[email protected]>

index 3abcb2ce5b7d..19dae28904f7 100644
@@ -485,9 +485,8 @@ static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
 	kvm->mmu_notifier_count++;
 	need_tlb_flush = kvm_unmap_hva_range(kvm, range->start, range->end,
 					     range->flags);
-	need_tlb_flush |= kvm->tlbs_dirty;
 	/* we've to flush the tlb before the pages can be freed */
-	if (need_tlb_flush)
+	if (need_tlb_flush || kvm->tlbs_dirty)
 		kvm_flush_remote_tlbs(kvm);
 
 	spin_unlock(&kvm->mmu_lock);