[RFC PATCH v2 6/8] KVM: arm64: Only write protect selected PTE

[Shameer Kolothum]

From: Keqian Zhu <zhukeqian1 at huawei.com>

This function write protects all PTEs between the ffs and fls of mask.
There may be unset bits between this range. It works well under pure
software dirty log, as software dirty log is not working during this
process.

But it will unexpectly clear dirty status of PTE when hardware dirty
log is enabled. So change it to only write protect selected PTE.

Signed-off-by: Keqian Zhu <zhukeqian1 at huawei.com>
Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi at huawei.com>
---
 arch/arm64/kvm/mmu.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index f5ae4b97df4d..34251932560e 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1132,10 +1132,17 @@ void kvm_arch_mmu_enable_log_dirty_pt_masked(struct kvm *kvm,
 	phys_addr_t base_gfn = slot->base_gfn + gfn_offset;
 	phys_addr_t start = (base_gfn +  __ffs(mask)) << PAGE_SHIFT;
 	phys_addr_t end = (base_gfn + __fls(mask) + 1) << PAGE_SHIFT;
+	int rs, re;
 
 	lockdep_assert_held_write(&kvm->mmu_lock);
 
-	stage2_wp_range(&kvm->arch.mmu, start, end);
+	for_each_set_bitrange(rs, re, &mask, BITS_PER_LONG) {
+		phys_addr_t addr_s, addr_e;
+
+		addr_s = (base_gfn + rs) << PAGE_SHIFT;
+		addr_e = (base_gfn + re) << PAGE_SHIFT;
+		stage2_wp_range(&kvm->arch.mmu, addr_s, addr_e);
+	}
 
 	/*
 	 * Eager-splitting is done when manual-protect is set.  We
-- 
2.34.1