[PATCH 1/3] KVM: x86/mmu: Fix off-by-1 when splitting huge pages during CLEAR

[David Matlack <dmatlack@google.com>]

Fix an off-by-1 error when passing in the range of pages to
kvm_mmu_try_split_huge_pages() during CLEAR_DIRTY_LOG. Specifically, end
is the last page that needs to be split (inclusive) so pass in `end + 1`
since kvm_mmu_try_split_huge_pages() expects the `end` to be
non-inclusive.

At worst this will cause a huge page to be write-protected instead of
eagerly split, which is purely a performance issue, not a correctness
issue. But even that is unlikely as it would require userspace pass in a
bitmap where the last page is the only 4K page on a huge page that needs
to be split.

Reported-by: Vipin Sharma <vipinsh@google.com>
Fixes: f2928aae8b9a ("UPSTREAM: KVM: x86/mmu: Split huge pages mapped by the TDP MMU during KVM_CLEAR_DIRTY_LOG")
Signed-off-by: David Matlack <dmatlack@google.com>
---
 arch/x86/kvm/mmu/mmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index f7901cb4d2fa..6aa966631cab 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -1382,7 +1382,7 @@ void kvm_arch_mmu_enable_log_dirty_pt_masked(struct kvm *kvm,
 		gfn_t end = slot->base_gfn + gfn_offset + __fls(mask);
 
 		if (READ_ONCE(eager_page_split))
-			kvm_mmu_try_split_huge_pages(kvm, slot, start, end, PG_LEVEL_4K);
+			kvm_mmu_try_split_huge_pages(kvm, slot, start, end + 1, PG_LEVEL_4K);
 
 		kvm_mmu_slot_gfn_write_protect(kvm, slot, start, PG_LEVEL_2M);
 
-- 
2.42.0.820.g83a721a137-goog